Development Answers (No Questions)

Can not remote desktop - no Terminal Server License Servers available

2011-10-19T12:18:00.000+11:00

Keywords:
remote desktop console disconnected terminal server license "no Terminal Server License Servers available"

Problem:
On trying to remote desktop to a machine get the popup message:

The remote session was disconnected because there are no Terminal Server License Servers available to provide a license.
Please contact the server administrator.

A quick search suggests:

Restarting the "Terminal Server" can help
but lets say (hypothetically) that we don't know where this is and/or how to do it.
Installing a Microsoft 'Hotfix'
but after accepting the terms; filling in the hotfix request form; getting the email with the link to the hotfix executable - we (at the moment anyway) get a 500 Internal Server Error on the MS hotfix download site.

If you just need to access the machine is there another option?

Solution:
You can remote desktop to the "console" - this is effectively like 'physically' logging into the machine rather than a remote session.

mstsc /console

or on Vista / Windows Server 2008:

mstsc /admin

mstsc allows specifying the machine on the command line itself to avoid the computer selection popup (use /help option for other options):

mstsc /v:remote-server /admin

Be aware that - if someone else had a console session on this machine they'd be kicked off. If you're logged on in console/admin mode anyone with access to the terminal - if it's plugged into a monitor for example - will see what you're doing.

Get the generated source code for JSPs in WebLogic

2011-09-21T16:27:00.002+10:00

Keywords:
generated JSP java class source Oracle WebLogic line numbers

Problem:
Given a stack trace such as the following:

java.lang.NullPointerException
 at jsp_servlet._web_45_inf._jsp._demo.__example._jspService(__example.java:117)
 at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
 at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
 at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
 at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
 at weblogic.servlet.internal.ServletStubImpl.onAddToMapException(ServletStubImpl.java:416)
 at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:326)
 at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
 at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:526)
 at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)

It won't always be obvious what the issue in example.jsp corresponds to in the generated __example.java. How do you get at the generated source code for the JSPs?

Solution:
The solution involves configuring a [app_name]/WEB-INF/weblogic.xml file in your web-app. The documentation is in the WebLogic 10.3 docs - see weblogic.xml Deployment Descriptor Elements but keep in mind the file will be validated against the schema so the elements must be in the correct spot.

Below is an example - defining the jsp-descriptor with keepgenerated and working-dir elements:

<?xml version="1.0" encoding="UTF-8"?>
<weblogic-web-app
    xmlns="http://www.bea.com/ns/weblogic/90"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.bea.com/ns/weblogic/90 http://www.bea.com/ns/weblogic/90/weblogic-web-app.xsd">
    <jsp-descriptor>
        <keepgenerated>true</keepgenerated>
        <working-dir>c:/my_folder/temp</working-dir>
    </jsp-descriptor>
    <container-descriptor>
        <prefer-web-inf-classes>true</prefer-web-inf-classes>
    </container-descriptor>
</weblogic-web-app>

Beware: an empty string in Oracle is NULL

2011-08-25T11:41:00.005+10:00

Keywords:
empty string '' CLOB varchar varchar2 text null isnull nvl NullPointerException JDBC

Problem:
There's code that is (seemingly) working with writing strings to CLOB columns and with the code from a previous post (Convert Oracle CLOBs to String) the reading of strings from the CLOB columns is working ok too ... until we get to empty strings - could it be that something is converting '' to NULL?

Here's a test case:

create table test_clobtext(

      id   number

    , text clob

);

insert into test_clobtext values (1, 'some clob text');

insert into test_clobtext values (2, '');

select id, text from test_clobtext;

You get:

        ID TEXT

---------- ----------------

         1 some clob text

         2

What's the value in the 2nd row? You can use the NVL() (which is just like ISNULL()):


select id, NVL(text,'IT IS A NULL') as text from test_clobtext;

Shock, horror, this is the result:

        ID TEXT

---------- ----------------

         1 some clob text

         2 IT IS A NULL

... and because I'm still in disbelief:


select id, NVL(text,'IT IS A NULL') as text from test_clobtext

where text IS NULL;

This is definitely the result:

        ID TEXT

---------- ----------------

         2 IT IS A NULL

So it's something to do with CLOBs? No, changing the text column to a varchar or varchar2 and you will get the same result! Is this right?

Solution:
This is apparently a well known issue (that I've only just stumbled across). A discussion is on stackoverflow: Why does Oracle treat empty string as NULL which links to more details information on ask-tom: Strings of Zero Length Not Equivalent To NULL.

It would seem that there are some scenarios where it won't be NULL but I can't reproduce this - changing the test case to have text as a char(1) still gives me NULL for the column.

The bottom line is if you're working with strings/text in a Oracle database you must expect and handle NULL values coming back - there will be no way to distinguish between whether what was originally stored was actually a NULL or an empty string ('').

Notes:
If you're dealing with CLOB columns you do have the option of storing (vendor specific) empty_clob() where you do want to distinguish between the cell being set to empty from it not being set at all (ie NULL). This post "An Empty Clob is not NULL" is a good discussion.

Convert Oracle CLOBs to String in JSTL and tag file

2011-06-20T13:22:00.007+10:00

Keywords:
java.lang.ClassCastException oracle.sql.CLOB cast java.lang.String CLOB jstl tag requestScope requestContext pageContext jspContext

Problem:
It's annoying when SQL that works for other vendors fails for a specific one ... in this case a "text" column in a schema is defined as "clob" in the corresponding oracle schema. Problem is that this is not necessarily equivalent - especially when querying the data. This is even more complex when the SQL is in JSTL. So with the JSTL code (where textValue is a CLOB):


<sql:query var="data" >

    select id, 

    textValue 

    from example 

    where id=?

    <sql:param value="${param['id']}"/>

</sql:query>

<c:forEach items="${data.rows}" var="row">

    <c:out value="${row.textValue}"/><br/>

</c:forEach>

You get the result:


oracle.sql.CLOB@e645e0

oracle.sql.CLOB@1f58913

oracle.sql.CLOB@fa6b82

...

Or if you try to use the textValue in something expecting a string, you'll get:

java.lang.ClassCastException: oracle.sql.CLOB cannot be cast to java.lang.String

How do you turn a Clob to a String without filling the JSP with vendor-specific code (leaving out the argument for not having SQL in the JSP for now)?

Solution:
Great discussion of this very issue is on the OTN Forum: JSP and CLOB. It essentially involves putting the Clob to String code in a scriptlet. To keep this vendor-neutral and take some of the "ugliness" out of the JSP I'd opt for putting this code in a tag file and stick to referencing just the java.sql.* interfaces.

Step 1: create a `/WEB-INF/tags/to-string.tag` tag file

(Or in a subfolder - the path must start with /WEB-INF/tags/.. if using the tagdir approach).

This takes the CLOB (or other) column value and sets it back in the request context as a String.


<%-- 

    Can turn a CLOB to String for Oracle schema

--%>

<%@ tag body-content="empty" %>

<%@ attribute name="var" required="true" type="java.lang.String" %>

<%@ attribute name="value" required="true" type="java.lang.Object" %>



<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>



<%@ tag import="java.sql.*" %>

<%@ tag import="javax.servlet.jsp.*" %>

<%

    String strValue = null; 

    if (value == null) {

        strValue = ""; // NB: oracle empty string is null

    } else if (value instanceof Clob) {

        Clob clob = (Clob)value;

        long size = clob.length();

        strValue = clob.getSubString(1, (int)size);

    } else {

        strValue = value.toString();

    }

    jspContext.setAttribute(var, strValue, PageContext.REQUEST_SCOPE);

%>

In this tag file, var is the name of the variable to define in the requestScope. Note how this is done by referencing the jspContext variable.

Step 2: Use the `to-string` tag for your `text`, `clob` or Other columns

This involves first defining the new taglib (putting all .tag files in tagdir in the JSP scope using the "eg" prefix in this example) and then simply using the eg:to-string tag to put the string-value of the column in a "local" requestScope variable.


<%@ taglib prefix="eg" tagdir="/WEB-INF/tags" %>

<sql:query var="data" >

    select id, 

    textValue 

    from example 

    where id=?

    <sql:param value="${param['id']}"/>

</sql:query>

<c:forEach items="${data.rows}" var="row">

    <eg:to-string var="textValue" value="${row.textValue}"/>

    <c:out value="${textValue}"/><br/>

</c:forEach>

IIS7 hiding tomcat webapp error pages

2011-04-05T13:06:00.006+10:00

Keywords:
IIS IIS7 custom error pages hiding masking tomcat 500 webapp error page jk connector AJP

Problem:
With tomcat integrated into IIS7 using the jk connector error pages from the webapp that have the http-response status set (eg to 500) get "replaced" with a generic IIS custom error page:


500 - Internal server error. 
There is a problem with the resource you are looking for, and it cannot be displayed

A quick web-search reveals it's a common issue for ASP.NET developers and the solution is simply to make changes to the ASP.NET application config or in code setting a special HttpResponse.TrySkipIisCustomErrors property(!) ... but what are the options for when the pages are being supplied by an ISAPI redirector/plugin (i.e. the JK connector in this case)?

Solution:
Based on the detailed notes on the IIS Blog (What to expect from IIS7 custom error module) the minimal steps required seem to be the following:

Step 1: create a `Web.config` file in the root folder of the Web Site

This is the Web Site where you've configured the "jakarta" virtual directory. If it's "Default Web Site" this may be C:\inetpub\wwwroot but check the properties to be sure (Right click Web Site > Manage Web Site > Advanced Settings ... and note the setting for 'Physical Path').

Step 2: add configuration to the `Web.config` file

<configuration>
   <system.webServer>
      <httpErrors errorMode="Detailed" existingResponse="Auto" />
   </system.webServer>
</configuration>

Step 3: restart the web site

Eg Right click Web Site > Manage Web Site > Restart

Be sure to to test this on the local machine (where IIS7 is installed) and from another machine in the network as IIS may give different error-page behaviour for local and 'remote' requests.

NTLM from an Axis (SOAP) service client - in 3 steps

2011-03-08T15:15:00.006+11:00

Keywords:
NTLM authentication Negotiate Apache axis SOAP IIS Windows Integrated Authentication CommonsHTTPSender NTCredentials

Problem:
Authenticating a service request with BASIC authentication is (relatively) straightforward:


        import java.net.URL;

        import org.apache.axis.client.Stub;

        import com.example.service.Example;

        import com.example.service.ExampleServiceLocator;

        import com.example.service.ExampleRequest;

        import com.example.service.ExampleResponse;



        // get access to the web service

        ExampleServiceLocator locator = new ExampleServiceLocator();

        String serviceURL = "http://server/application/services/example";

        Example example = locator.getexample(new URL(serviceURL));

        // set credentials 

        ((Stub)example).setUsername("myusername");

        ((Stub)example).setPassword("mypassword");

        

        // setup request

        ExampleRequest request = new ExampleRequest();

        request.setProperty("SomeProperty");

        

        ExampleResponse response = example.example(request);

What if the (SOAP) service being called required NTLM authentication (e.g. the service is running in IIS and security is set as "Windows Integrated Authentication")?

Solution:
The following three steps are assuming Axis 1.x. The Apache Axis Client Tips and Tricks is a good reference, in particular for step 2, but also for other "tips".

Step 1: Add Apache commons-httpclient (3.1) and commons-codec libraries

Note you must add the commons httpclient jar file and not the (latest/refactored) apache httpclient to the project - or you will get ClassNotFound exceptions.

Step 2: Define custom client-config with CommonsHTTPSender

It's mentioned in the "Tips and Tricks" article mentioned above, but you can either: (a) define a custom client-config.wsdd file in the classpath before axis.jar; (b) edit the generated ...ServiceLocator.java generated class and make it override getEngine...; or (c) at runtime simply feed the customised config XML to your ...ServiceLocator object.

I prefer the latter - for example, define a static method with the config XML as a string:


    protected static org.apache.axis.EngineConfiguration getEngineConfiguration() {

        java.lang.StringBuffer sb = new java.lang.StringBuffer();

        sb.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n");

        sb.append("<deployment name=\"defaultClientConfig\"\r\n");

        sb.append("xmlns=\"http://xml.apache.org/axis/wsdd/\"\r\n");

        sb.append("xmlns:java=\"http://xml.apache.org/axis/wsdd/providers/java\">\r\n");

        // sb.append("<transport name=\"http\" pivot=\"java:org.apache.axis.transport.http.HTTPSender\" />\r\n");

        sb.append("<transport name=\"http\" pivot=\"java:org.apache.axis.transport.http.CommonsHTTPSender\" />\r\n");

        sb.append("<transport name=\"local\" pivot=\"java:org.apache.axis.transport.local.LocalSender\" />\r\n");

        sb.append("<transport name=\"java\" pivot=\"java:org.apache.axis.transport.java.JavaSender\" />\r\n");

        sb.append("</deployment>\r\n");

        org.apache.axis.configuration.XMLStringProvider config = 

            new org.apache.axis.configuration.XMLStringProvider(sb.toString());

        return config;

    }

Then the call to the locator would become:


        // get access to the web service

        ExampleServiceLocator locator = new ExampleServiceLocator(getEngineConfiguration());

Step 3: Set the username as `DOMAIN\username`

Set the username as you did with BASIC authentication but you must ensure is set in the form DOMAIN\username (keeping in mind that if expressing this in java code - as a string - or as a property value in a properties file this would be set as "DOMAIN\\username" - \\ being the escape sequence for \):


        ((Stub)example).setUsername("MY_NT_DOMAIN\\myusername");

        ((Stub)example).setPassword("mypassword");

With the above 3 steps covered you're using NTLM.

Notes:
Avoid setting the system property -Djava.ext.dirs as the above relies on the sunjce_provider.jar library which is in JRE_HOME\lib\ext by default. Ext-path problems may give you errors such as:
"Cannot find any provider supporting DES/ECB/NoPadding"

Failing to set the username in the form DOMAIN\username will result in the error:

org.apache.commons.httpclient.auth.InvalidCredentialsException: 

    Credentials cannot be used for NTLM authentication: 

        org.apache.commons.httpclient.UsernamePasswordCredentials

 at org.apache.commons.httpclient.auth.NTLMScheme.authenticate(NTLMScheme.java:332)

 at org.apache.commons.httpclient.HttpMethodDirector.authenticateHost(HttpMethodDirector.java:282)

 at org.apache.commons.httpclient.HttpMethodDirector.authenticate(HttpMethodDirector.java:234)

 at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:170)

 at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)

 at org.apache.axis.transport.http.CommonsHTTPSender.invoke(CommonsHTTPSender.java:186)

This is because the format of the username determines the Credentials instance created. With the DOMAIN\... prefix on the username you get an instance of org.apache.commons.httpclient.NTCredentials rather than org.apache.commons.httpclient.UsernamePasswordCredentials - which as the message explains can't be used for NTLM.

Is the IBM DB2 UDB service not running? Can't make JDBC Type 4 connections

2011-01-28T08:41:00.010+11:00

Keywords:
IBM DB2 v8 UDB Universal Driver TCP/IP which port windows service JDBC Type 4

Problem:
Attempting to make a JDBC Type 4 connection (ie pure java talking TCP/IP, no native code) to the DB2 server gives me:


com.ibm.db2.jcc.b.SqlException: IO Exception opening socket to server <myservername> on port 50000. 
The DB2 Server may be down.

The DB2 server (running on Windows) is definitely running. In DB2 "Control Center" the "instance" ("DB2" the default name?) is definitely started. Looking at the local TCP ports being listened via netstat -abno there's no 50000 or anything close. So either the service that accepts the Type-4 JDBC connections (UDB) is not running or it's listening on a different port. How do you check?

Solution:
I couldn't find any mention of this in searching (though I did find "DB2 Version 8 Connectivity Cheat Sheet" which is good reference for DB2 generally), but by accident I stumbled on "Setup communications..." on right clicking the "DB2" instance in DB2 Control Center. From here the rest is straight forward:

so, right click the "DB2" instance and select "Setup communications..."

check TCP/IP

click the Properties button and then just click the Default button to get default values
- Note the port number: 50000 by default

after clicking OK from the Properties and the communications dialog you'll have to restart the instance
- right click the "DB2" instance and select Stop and then Start

Now when you check the open ports via netstat -abno you should hopefully see:


  TCP    0.0.0.0:50000          0.0.0.0:0              LISTENING       3012
  [db2syscs.exe]

To recap the IBM DB2 Universal Driver Type 4 (thin) connection details:

Driver Class:	`com.ibm.db2.jcc.DB2Driver`
URL:	`jdbc:db2://<host>[:<port>]/<database_name>` eg:`jdbc:db2://myservername:50000/MYDATABASE`
Driver Class:	`com.ibm.db2.jcc.DB2Driver`
Jar file(s):	`db2jcc.jar` & `db2jcc_license_cu.jar`

Type coercion in JSTL - for sql:param

2010-08-18T15:31:00.005+10:00

Keywords:
jstl sql integer string type coercion postgres serial operator does not exist: bigint = character varying

Problem:
After upgrading from PostgreSQL 8.0 to 8.4 the following JSTL that queries a table by a passed in "ID":


<sql:query var="examples" dataSource="${exampleDataSource}">
    select ExampleName as "name"
    from ExampleTable 
    where ExampleId = ?
    order by ExampleName ASC
    <sql:param value="${param['ID']}"/>
</sql:query>

Fails with the exception:


javax.servlet.jsp.JspException:
    select ExampleName as "name"
    from ExampleTable
    where ExampleId = ?
    order by ExampleName ASC

: ERROR: operator does not exist: bigint = character varying
        at org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.doEndTag(QueryTagSupport.java:220)
        ....
Caused by: java.sql.SQLException: ERROR: operator does not exist: bigint = character varying
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1471)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1256)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:175)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:330)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:240)
        at org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:93)
        at org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.doEndTag(QueryTagSupport.java:215)

Why are there data type errors all of a sudden? ... and how do you fix it?

Solution:
There is normally Type Coercion for EL expressions but it's a bit vague for sql:param. Ideally it should coerce the param into the type required but this would require knowing the schema & the SQL being executed. So looking at the source for QueryTagSupport it will just call setObject using the default type that was supplied in the param.

Contrary to the sql:param documentation the value does not have to be a String.

To get the right type into sql:param use type coercion in EL before the param gets the value. To coerce a String to Integer, you could multiply by 1. For example:


<sql:query var="examples" dataSource="${exampleDataSource}">
    select ExampleName as "name"
    from ExampleTable 
    where ExampleId = ?
    order by ExampleName ASC
    <sql:param value="${param['ID']*1}"/>
</sql:query>

Or in two steps:


<c:set var="exampleId" value="${param['ID']*1}"/>
<sql:query var="examples" dataSource="${exampleDataSource}">
    select ExampleName as "name"
    from ExampleTable 
    where ExampleId = ?
    order by ExampleName ASC
    <sql:param value="${exampleId}"/>
</sql:query>

Why did this come up after a PostgreSQL upgrade? It seems something to do with different handling of the SERIAL data type which is now compiled to it's actual representation of integer with sequence rather than leaving it as it's "notational convenience" name. Perhaps the PostgreSQL JDBC will coerce a String to a serial but not an integer?

It's hard to say the above work around is best practice but it will be harmless for databases that handle coercion at the JDBC level and necessary for those that don't.

Stop AXIS output of anonymous complex types in xsi:type

2010-06-03T11:29:00.007+10:00

Keywords:
apache axis xsi:type anonymous complex type .NET "No type definition found for the type referenced by the attribute 'xsi:type'"

Problem:
The schema definition for a response element may define the complex type "inline" rather than by reference. This is known as an "anonymous type". Eg:

<xs:element name="MyResponse">
    <xs:annotation>
        <xs:documentation>This is the root element of the Response.</xs:documentation>
    </xs:annotation>
    <xs:complexType>
        <xs:sequence>
            <xs:element name="PropertyOne" type="xs:string" minOccurs="0"/>
            <xs:element name="PropertyTwo" type="xs:string" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
</xs:element>

When axis generates the SOAP response (with the default settings) this includes xsi:type attributes. Eg:

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
     <MyResponse xsi:type="ns1:MyResponse" xmlns="http://example.com/service" xmlns:ns1="http://example.com/service">
        ...

This is accepted by AXIS-generated client code but in .NET (and other schema-validating tools such as XMLSpy) you'll get an error along the lines of


No type definition found for the type referenced by the attribute 'xsi:type'='ns1:MyResponse' of element <MyResponse>

The error inidicates validation is probably doing the right thing with the xsi:type attribute and checking it - there is actually no type with this name, it's anonymous. Can the behavour in AXIS be changed?

Solution:
Thankfully there is a configuration setting in AXIS to stop this output - sendXsiTypes, which is true by default:

<parameter name="sendXsiTypes" value="false"/>

There are a number of ways to get this setting in there. I'd recommend creating a wsdd deploy file for just the globalConfiguration and deploy this to the AXIS AdminServlet as you would do with the deploy.wsdd definitions for the other service(s).
So an example globalConfig-deploy.wsdd:


<deployment xmlns="http://xml.apache.org/axis/wsdd/"
    xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">
    <globalConfiguration>
        ...
        <parameter name="sendXsiTypes" value="false" />
        ...
    </globalConfiguration>
</deployment>

You'll find the MyApp/WEB-INF/server-config.wsdd will then be updated and the SOAP excludes this attribute as advertised:

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
     <MyResponse xmlns="http://example.com/service">
        ...

The alternative to this (if you do want the xsi:type attributes) is to define explicit types for your root response elements. Eg:

<xs:element name="MyResponse" type="MyResponseType">
    <xs:annotation>
        <xs:documentation>This is the root element of the Response.</xs:documentation>
    </xs:annotation>
</xs:element>
<xs:complexType name="MyResponseType">
    <xs:annotation>
        <xs:documentation>This is the type for the root element of the Response.</xs:documentation>
    </xs:annotation>
    <xs:sequence>
        <xs:element name="PropertyOne" type="xs:string" minOccurs="0"/>
        <xs:element name="PropertyTwo" type="xs:string" minOccurs="0"/>
    </xs:sequence>
</xs:complexType>

The XML from AXIS will then include xsi:type but the value will be correct - referencing a type that does exist. Eg:

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Body>
     <MyResponse xsi:type="ns1:MyResponseType" xmlns="http://example.com/service" xmlns:ns1="http://example.com/service">
        ...

Enable debug/trace level logging for Tomcat 6 Realms

2010-03-03T10:53:00.010+11:00

Keywords:
tomcat 6 realm logging juli logging.properties debug="9" debug="99" debug="true" JNDIRealm trace verbose jndi realm JNDIRealm

Problem:
Apparently Tomcat 6 Logging is greatly improved ... more granularity, flexibility in choosing java.util.logging or log4j, etc. This is great, but I'm happy with the default logging - ie if something goes wrong let me get the detail from a log file.

This attitude hits a snag where things go wrong and there's nothing in the logs - in my case, setup of a com.speedlegal.catalina.realm.JNDIRealm is not letting me in but there's no details why. It used to be a matter of simply setting debug="9" on the Realm definition and you have verbose logging - the examples in the Tomcat 6 Realm documentation still use this:

<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
    connectionURL="ldap://localhost:389"
    userPattern="uid={0},ou=people,dc=mycompany,dc=com"
    roleBase="ou=groups,dc=mycompany,dc=com"
    roleName="cn"
    roleSearch="(uniqueMember={0})"
/>

But this has no effect on logging. You'll get a warning telling you as much:

03/03/2010 10:56:08 AM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Realm} Setting property 'debug'
 to '99' did not find a matching property.

What's the minimum I have to do to enable debug?

Solution:
You have to edit the $CATALINA_HOME/conf/logging.properties file.

1. Configure debug logging for Realms and Authentication

Insert the following lines (in blue):

############################################################
# Facility specific properties.
# Provides extra control for each logger.
############################################################
# This would turn on trace-level for everything
# the possible levels are: SEVERE, WARNING, INFO, CONFIG, FINE, FINER, FINEST or ALL
#org.apache.catalina.level = ALL
#org.apache.catalina.handlers = 2localhost.org.apache.juli.FileHandler
org.apache.catalina.realm.level = ALL
org.apache.catalina.realm.useParentHandlers = true
org.apache.catalina.authenticator.level = ALL
org.apache.catalina.authenticator.useParentHandlers = true

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = 2localhost.org.apache.juli.FileHandler

This will give you debug/trace level logging to console and the file assuming you've kept the default config. But you only see debug in the console, not the catalina.[date yyyy-MM-dd].log file - in fact, the log file empty? The buffering means the file-logging is only written when the buffer is full.

2. Disable buffering for FileHandler logging

(until the issue is resolved of course) Insert the line (in blue):


1catalina.org.apache.juli.FileHandler.level = FINE
1catalina.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
1catalina.org.apache.juli.FileHandler.prefix = catalina.
1catalina.org.apache.juli.FileHandler.bufferSize = -1

These two inserts give you pretty much the equivalent of the old debug="9" and you'll (hopefully) get the verbose information required - happy debugging ...

Configure endorsed libraries in Tomcat 6

2010-02-18T16:01:00.002+11:00

Keywords:
Tomcat 6 endorsed java.endorsed.dirs Endorsed Standards Override Mechanism XML libraries xerces

Problem:
If your webapp needs its own XML libraries (xerces in particular) how do you get Tomcat 6 to use this and not the JAXP APIs packaged into the JSE? This used to be as simple as dropping them into ${CATALINA_BASE}/common/endorsed but there's only a ${CATALINA_BASE}/lib folder ...

Solution:
Thankfully found the solution in this blog (and comments).

Simply, create a ${CATALINA_BASE}/endorsed folder and drop the jar files in there. Tomcat will be setup to use this if it exists.

Notes:
No explicit mention of this in Tomcat 6 Class Loader notes

It does note the -Djava.endorsed.dirs system property is set but you need to check setclasspath.[bat|sh] for when it's set and what it's set to by default - ie ${CATALINA_BASE}/endorsed.

HSQL random function - calling scalar functions via JDBC

2010-02-04T16:02:00.008+11:00

Keywords:
HSQL JDBC select random scalar built-in function rand fn

Problem:
I want to demstrate database interaction but the data doesn't really matter in this case. HSQL is ideal because you can set a connection to in-memory database .. but there's no data. Random would do, is there a random function in HSQL? Where is the function reference? Is it called rand(), random() or other?

Solution:
Short answer is it's called "rand". So the SQL would be:

CALL rand()

With JDBC this is:

PreparedStatement stmt = connection.prepareStatement("CALL rand()");
stmt.execute();

... and I can't find a complete function reference for HSQL.

Digging a bit further there is JDBC convention for calling scalar/built-in function in a vendor independent way - See JDBC 2.0: Escape Syntax and Scalar Functions. This involves the use of the "fn" keyword and braces - so the syntax is:

{fn <function()>}

Whether the JDBC driver recognises the syntax and maps it correctly to the underlying function ("rand" is called "random" in postgres for example) is up to the vendor. I can confirm that HSQL seems to handle most numeric, string and date functions (as mentioned above, can't find doco for this. The derby JDBC function reference is a reasonably good overview). So the vendor agnostic random call becomes:

PreparedStatement stmt = connection.prepareStatement("CALL {fn rand()}");

Notes:
What I could find was documentation of HSQL "Java Stored Procedures". This effectively lets you call any public static java method (from a class in the classpath) right there in the SQL statement. So, yet another (non-JDBC standard) way of making the random call would be:

CALL "java.lang.Math.random"()

... or doing more work in the SQL:

CALL "java.lang.Math.floor"("java.lang.Math.random"() * 100)

Pretty cool, I must think of a use for this :)

Is Eclipse deleting XML resources from my build path?

2009-09-08T17:29:00.003+10:00

Keywords:
eclipse 3.4.0 ganymede FileNotFoundException xml properties build classpath filtered resources deleted excluded "class path resource cannot be resolved"

Problem:
I have a project where configuration resources (mostly hibernate - hibernate.cfg.xml & *.hbm.xml) exist in the same folders as the java source and it's expected that these are copied to the build output so they can be loaded from the classpath.

It seems eclipse is "cleaning up" the XML files from the build output folder. Check the include/exclude settings on the project and Included is set to (All). Adding *.xml explicitly to the included list makes no difference.

Out of curiosity, manually copying an XML file to the build output folder and refreshing the project causes the XML to be deleted. Why?

Solution:
I'm not sure if it was an update or plugin that caused this, but the problem is with the Filtered Resources setting.

In Window -> Preferences:
go to: Java > Compiler > Building
in Output folder section:

check the Filtered resources value
if *.xml is in the comma separated list, this is the cause.
Remove from the list and allow the Project rebuild.

As mentioned, even if you explicitly add *.xml to be included in your Project settings the above global setting will cause it to be excluded.

JSTL formatNumber as percentage gets invalid attribute error

2009-06-19T17:08:00.004+10:00

Keywords:
fmt:formatNumber <formatNumber> invalid type attribute: "percentage" percent

Problem:
The JSTL Tag Library documentation seems to indicate that to format a number as a percentage you'd use:


<fmt:formatNumber type="percentage" value="0.5"/>

This gives the error message
<formatNumber>, invalid type attribute: "percentage"

Solution:
Although the documentation for type says "Specifies whether the value is to be formatted as number, currency, or percentage" these aren't the possible values - it's "percent" for percentage:


<fmt:formatNumber type="percent" value="0.5"/>

Notes:
If you know a good reference for JSTL I'd like to know ...

The Appendix A from JSTL in Action is not bad - it documents possible values for formatNumber type at least.

Eclipse build errors - java.lang.object cannot be resolved

2009-06-16T10:46:00.008+10:00

Keywords:
eclipse 3.4.0 ganymede The type java.lang.object "cannot be resolved" "Cannot find the class file" "refers to the missing type"

Problem:
Opened eclipse, it needed to do a full workspace build (probably because ant scripts have updated class files and it needs to refresh). Random classes in the project now no longer compile. Examples of the errors being reported:

Description	Resource	Path	Location	Type
`The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files`	`MyClass.java`	`MyProject/src/com/example`	`line 1`	`Java Problem`
`The project was not built since its build path is incomplete. Cannot find the class file for java.lang.Object. Fix the build path then try building this project`		`MyProject`	`Unknown`	`Java Problem`
`The method myMethod(SomeClass) from the type MyOtherClass refers to the missing type (insert java type here: InputStream\|File\|Vector\|IOException\|etc)`	`MyOtherClass.java`	`MyProject/src/com/example`	`line 123`	`Java Problem`

Solution:
It sounds like this has been a known issue (Bug 67414)that was resolved in 3.0 ... someone has commented that it's occurring for them in 3.4 as well.

In the mean time, the work around is to remove the JRE System Library from the project and then add it back again.
Here are the steps:

Go to properties of project with the build error (right click > Properties)

View the "Libraries" tab in the "Build Path" section

Find the "JRE System Library" in the list (if this is missing then this error message is not an eclipse bug but a mis-configured project)

Remove the "JRE System Library"

Hit "Add Library ...", Select "JRE System Library" and add the appropriate JRE for the project (eg. 'Workspace default JRE')

Hit "Finish" in the library selection and "OK" in the project properties and then wait for the re-build of the project

Hopefully the error will be resolved ...

Javascript history.back() not working for iframes in Firefox

2009-05-08T12:33:00.004+10:00

Keywords:
javascript history frame iframe go(-1) back firefox 3 top self

Problem:
You can get a hyperlink to behave as a "back" with a bit of javascript:


<a href="javascript:history.back()">back</a>

or (saying go back one place in the history - equivalent to the above):


<a href="javascript:history.go(-1)">back</a>

This works fine in all browsers when the page is in the main-view. If this javascript is encountered in an iframe you expect that you get the previous page that was loaded in that iframe. In firefox 3+ you're taken back in the main view page not the iframe - a nuisance if there's a detailed browsing history in the iframe view. Why does it work fine in other browsers and previous versions of firefox?

Solution:
I don't know why, but it seems that in firefox 3+ when you say history this becomes implicitly top.history. Someone has tried to raise this with mozilla with not much luck - javascript:history.back() and Firefox 3.0.1 and iframes.

The solution is to be explicit about which frame you want to navigate back with. If you just want all browsers to behave the same then self refers to the frame the user is clicking in (therefore in other browsers history is implicitly self.history). So the go-back hyperlink becomes:


<a href="javascript:self.history.back()">back</a>

or:


<a href="javascript:self.history.go(-1)">back</a>

This will behave the same regardless of if the page is loaded in the main-view or in an frame/iframe.

IE8 Compatibility Issues and working around them for HTML, Java and GWT

2009-04-08T14:25:00.008+10:00

Keywords:
IE8 compatibility X-UA-Compatible java filter http-equiv GWT "links not working" broken EmulateIE7 compliance

Problem:
You're either certain your website/webapp is broken in IE8 or suspect it might be. What can you do?

For browsers such as firefox and IE7, you used the DOCTYPE switch to indicate if it should treat your page as being in "standards" mode or "quirks" mode. As discussed on A List Apart "standards" is open to interpretation and even if the page didn't fully comply with the standard it referenced, it could expect the browser to have a reasonable crack at letting it work.

Not any more. IE8 renders all pages in standards mode by default and it's interpretation is as far as I can tell, stricter than any other browser. In this mode, many HTML, CSS and javascript/DOM elements (that were introduced by older versions IE! - and in some cases understood by other browsers such as firefox) are not just deprecated, they're completely not there - meaning any reference to them will in most cases stop the page/application working in the browser. When this happens, the page layout may be askew, links may stop working and miscellaneous javascript errors will be flagged in the status bar.

If you're not sure if your webpage/webapp is strictly standards compliant, it most probably isn't.

GWT is effected - see Dan Moore's post and GWT Issue #3329.

Solution:
IE8 users can make broken pages work again by opting-out of the "most strict" standards treatment on a site-by-site basis using the "Compatibility View" button but you can save them the trouble by using a new http-header tag X-UA-Compatible.

The A List Apart article above describes the merits of being able to target specific versions (and the comments seem to mostly disagree :) but in the majority of cases I imagine you just want the page to be treated the way IE7 did - "standards" mode (with "flexibility") for pages that require it and "quirks" mode for all others. So use the "IE=EmulateIE7" value by either:

making the server side code add this http header to every response
```
X-UA-Compatible: IE=EmulateIE7
```

or add the following meta tag to the <head> element of the page (which is essentially the equivalent to setting values on the http response)
```
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
```

You can cover the entire java web application by defining a filter as documented by Mark McLaren:


    public void doFilter(ServletRequest request, 
                         ServletResponse response, 
                         FilterChain chain)
            throws IOException, ServletException {
        if (response instanceof HttpServletResponse) {
            ((HttpServletResponse) response).setHeader("X-UA-Compatible", "IE=EmulateIE7");
        }
        chain.doFilter(request, response);
    }

Apache hosted sites can be covered by using mod_headers. For example, assuming you have the module loaded, add the following to the httpd.conf file:


Header add X-UA-Compatible "IE=EmulateIE7"

Notes:
Having trouble installing the release version of IE8? (for goodness sake, just get firefox :) But, if you really do want to get it working for yourself see Internet Explorer 8 is not supported on this operating system for a discussion of common issues.

XSLT output is missing the doctype

2009-02-13T14:32:00.004+11:00

Keywords:
xslt identity transform missing doctype Document Type java DOM

Problem:
Running an XSLT 'identity transform' I would expect the XML data out to be identical to the data in ... it almost is, but it's missing the doctype declaration.
Can you tell the XSTL to keep the doctype in?

Solution:
Apparently not ... I can't find a good reference for this, but it seems that the spec (or at least xalan) is a bit vague on how this should be handled. Proposed work-arounds seem to be hard-coding the doctype in the <xsl:output> element (if outputting to xml) or hiding the doctype in the XSLT via <xsl:text disable-output-escaping="yes">.

If you want to make the inclusion of the doctype generic there's no pure XSTL solution - you can add it after the transform, but even that is not straightforward using pure java DOM elements ... here is the code:


    // assuming there's an inputDocument
    TransformerFactory factory = TransformerFactory.newInstance();
    StreamSource stylesheet = new StreamSource(stylesheetData);

    DOMSource source = new DOMSource(inputDocument);
    DOMResult result = new DOMResult();

    Transformer transformer = factory.newTransformer(stylesheet);
    transformer.transform(source, result);

    Document outputDocument = (Document)result.getNode();
    if (inputDocument.getDoctype() != null) {
        DocumentType inputDocType = inputDocument.getDoctype();
        
        // you can't importNode for DocumentType nodes but you can create 
        // them via DOMImplementation from there insert is easy
        DOMImplementation domImpl = outputDocument.getImplementation();
        DocumentType outputDocType = domImpl.createDocumentType(
              inputDocType.getName()
            , inputDocType.getPublicId()
            , inputDocType.getSystemId());
        outputDocument.insertBefore(outputDocType, outputDocument.getDocumentElement());
    }

Notes:
It's interesting that this code is not allowed:


    DocumentType outputDocType = (DocumentType) outputDocument.importNode(inputDocType, true /*deep*/);

It seems DocumentType is a special element that can't be imported.

It's also interesting there's no method straight on the document:


    DocumentType outputDocType = outputDocument.createDocumentType(...);

The only way to get this kind of element is to obtain the special DOMImplementation object via the Document.getImplementation() method.

Quirks with the implementation? I've looked at this issue too long already to bother to find out why :)

GWT Button acts as a submit in WebKit browsers

2009-01-16T10:27:00.003+11:00

Keywords:
HTML button element form WebKit Chrome Safari iPhone

Problem:
In WebKit browsers, the Button widget in a GWT application seems to always act as a submit, regardless of event sinking (via ClickListener) behaviour added to it.

In Firefox (and IE!) the button works fine - that is the 'onclick' behaviour added to the widget via the GWT listening architecture is executed and the page is not submitted.

Solution:
A clue to the solution is in the code for the GWT Button (thank goodness for source code - see Button.adjustType(Element button)).

It seems to be a work around for Firefox. The W3C spec states that the default value for button type is 'submit'. Firefox does this explicitly in the DOM and when detected, this is fixed by the GWT JSNI (JavaScript Native Interface) code.

It would seem that for WebKit browsers this default is enforced but not made explicit in the DOM so this GWT snippet does not get a chance to resolve the issue. The work around is to always be explicit about the button type (as recommended in W3Schoools).

You do this in GWT as follows:


     Button b = new Button("click here");
     DOM.setElementAttribute(b.getElement(), "type", "button");

Redirect from a JSP page (to another server)

2008-10-17T16:44:00.005+11:00

Keywords:
best practice tips JSP redirect XML

Problem:
<jsp:forward> is not for redirecting to an external server (and the address you forward to will have access the request attributes and parameters, which may be desirable, see discussion here: when to use response redirect and jsp forward.

Is using response.sendRedirect(...) ok/best-practice?
Solution:
The short answer, is it's fine. In summary, there are four approaches I can think of:

Approach #1: Scriptlet to sendRedirect


<%
    response.sendRedirect("http://www.example.com");
%>

This has worked since the introduction of JSPs (see: Implementing a Redirect in a JSP Page) ... sometimes you need the servlet API in your JSP page either because there's other content (eg HTML) that makes it reasonable not to be a pure servlet. Other times it's just convenient to have a text file compiled on the fly.

Though there are many that would disagree (Sciptlet snobs? see How to redirect a page in JSP - I don't see why you'd get wound up about scriptlets. Why would you write a servlet when one line of code in a text file gives you the same result?).

Approach #2: Use Apache JSTL and the c:redirect tag


<c:redirect url="http://www.example.com"/>

or scriptlets again:


<c:redirect url="<%=scriptlet logic%>"/>

Sure, it's 'pure' XML but you'll need the taglib definition in the JSP file and include the JSTL jars in your web application - as discussed in the notes for a previous post.

Approach #3: Refresh meta tag

You could get the JSP to produce a HTML page that contains the Refresh meta tag.


<html>
<head>
  <meta http-equiv="Refresh" content="0; url=http://www.example.com/">
</head>
<body></body>
</html>

Where 0 is the delay in seconds. If more than zero, you'd probably want to put some text on the page to explain what's happening.

Approach #4: Javascript

As above, you could get the JSP to produce a HTML page that contains javascript to perform the redirect.


<html>
<head>
<script type="text/javascript">
window.location = "http://www.example.com/";
</script>
</head>
<body></body>
</html>

You could use setTimeout to get the redirect to happen after a period of milliseconds.

Notes:
Out of curiosity I checked TCP monitor for what the browser is actually receiving when you use Approach #1 or #2 (sendRedirect or c:redirect)


HTTP/1.1 302 Moved Temporarily
Location: http://www.example.com

So it saves you from 2 lines of servlet (or scriptlet) code:


response.setStatus(302);
response.setHeader("Location", "http://www.example.com");

So the difference to Approaches #3 & #4 isn't great or much more inefficient really, in all cases it's up to the browser to go to the specified address.

Comments in JSON

2008-10-10T12:02:00.003+11:00

Keywords:
comments JSON javascript

Problem:
Can you have comments in JSON?

Solution:
A discussion leading to the answer is on the Bytes IT forum.

Basically, though it's not defined in the JSON Grammar - on json.org - you can use slash-star /* ... */ comments to get most(?) javascript engines to ignore the comment text.

For example:


<script type="text/javascript">
    var nested_arrays = {
        cities: [
            ["Sydney", "Melbourne", "Canberra"]  /* Australia */
          , ["London", "Birmingham"]             /* UK */
          , ["Los Angeles", "New York"]          /* US */
        ]
    };
</script>

How do you remove a windows service?

2008-08-15T08:52:00.003+10:00

Keywords:
manually remove windows service registry sc

Problem:
OK, I've uninstalled some software but it's left a service definition. It can't do much harm as most (but not all) of the resources it needs have been removed ... but I can't ignore it - how do you get rid of it?

Note to self: before uninstalling software with services it may help to stop them all and possibly disable them all too? I think this is why this particular thing could not be removed.

Note to developers: stop and remove services as part of uninstall programs.

Solution:
Some solutions talk about using regedit and modifying:


HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services

A better approach is to use sc ".. a command line program used for communicating with the Service Control Manager and services".

It should be as simple as:


sc delete [service name]

But the tricky thing is getting the name of the service right. What you see in the Service window is the display name not the service name. Use:


sc query state= all

To get a listing like


...
SERVICE_NAME: ExampleService
DISPLAY_NAME: Example Service That I Want To Delete
        TYPE               : 10  WIN32_OWN_PROCESS
        STATE              : 1  STOPPED
                                (NOT_STOPPABLE, NOT_PAUSABLE, IGNORES_SHUTDOWN))
        WIN32_EXIT_CODE    : 1077  (0x435)
        SERVICE_EXIT_CODE  : 0  (0x0)
        CHECKPOINT         : 0x0
        WAIT_HINT          : 0x0

...

SERVICE_NAME: helpsvc
DISPLAY_NAME: Help and Support
        TYPE               : 20  WIN32_SHARE_PROCESS
        STATE              : 4  RUNNING
                                (STOPPABLE, NOT_PAUSABLE, IGNORES_SHUTDOWN))
        WIN32_EXIT_CODE    : 0  (0x0)
        SERVICE_EXIT_CODE  : 0  (0x0)
        CHECKPOINT         : 0x0
        WAIT_HINT          : 0x0

...

So the above example listing:


sc delete ExampleService

Notes:
Just type sc at the command prompt for usage and more example commands (hit y to get help for the sc query commands).

HTTP Status 405 - HTTP method POST is not supported by this URL

2008-06-18T16:26:00.002+10:00

Keywords:
HTTP Status 405 - HTTP method POST is not supported by this URL form login tomcat

Problem:
What does this error mean when reported by tomcat?


HTTP Status 405 - HTTP method POST is not supported by this URL
Status report

HTTP method POST is not supported by this URL

The specified HTTP method is not allowed for the requested resource (HTTP method POST is not supported by this URL).

Solution:
Simple answer: your servlet needs to implement doPost(HttpServletRequest, HttpServletResponse). Your servlet probably already implements doGet() so if you don't care about implementing different logic for POST, then just get it to call doGet():


public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
        // same logic
        this.doGet(request, response);
}

Notes:
It's a bit confusing if the servlet is a login form. GET should be returning the login form, POST from this form is handled by j_security_check. But if the client's initial request was a POST then the login servlet just needs to implement doPost() to keep the servlet container happy (calling doGet() as mentioned above is fine).

It seems that the servlet container (tomcat at least) makes sure the data from the original POST is not lost once the user gets past the j_security_check: Tomcat - User - [is] post data lost when redirecting

get/decode/unescape parameters from URL using Javascript

2008-05-13T13:27:00.003+10:00

Keywords:
GET decode unescape request parameter param URL javascript

Problem:
You need to get at the (GET) parameters in the URL of the window with some client-slide javascript. There's no built in mechanism to access these by name in an unencoded way so it would seem you have to parse the window location ... this must have been done by some one before.

Solution:
Found two good blogs that discuss this:

Get URL Parameters Using Javascript - uses regular expressions

Get parameters from URL with JavaScript - uses substrings from the location.search (ie the query portion of the URL)

I found the second approach easier to read, but both miss unescaping the parameter value once obtained ... there's a built in function for that. So here's what I've used:


<script type="text/javascript">
/*
 * Retrieves the query parameter with the given parameter name or empty 
 * string if not defined
 * 
 * @param parameter name of the parameter to retrieve
 */
function queryParam(parameter) {
    var searchString = top.location.search;
    searchString = searchString.substring(1);// ommit the leading '?'

    var paramValue = '';
    var params = searchString.split('&');
    for (i=0; i<params.length;i++) {
        var paramPair = params[i];
        var eqlIndex = paramPair.indexOf('=');
        var paramName = paramPair.substring(0,eqlIndex);
        
        if (paramName == parameter) {
            paramValue = unescape(paramPair.substring(eqlIndex+1));
            return paramValue;
        }
    }
    return paramValue;
}
</script>

So from a URL http://www.example.com/formprocess?name=Fred%20Bloggs&date=01%2f01%2f2008
You can get the unescaped parameter values via:


var name = queryParam('name'); // 'Fred Bloggs'
var date = queryParam('date'); // '01/01/2008'

Notes:
This doesn't handle multi-valued parameters ... the first (regex) blog post has some comments on how to handle this.

Call a stored procedure from a JSP with JSTL

2008-04-09T10:58:00.005+10:00

Keywords:
Call execute SQL stored procedure JSP JSTL tag library

Problem:
The JSTL SQL tag library is a useful way of getting a rapid prototype going - it's all in a plain text file and will get compile on the fly. Examples I've seen show SELECT, UPDATE, INSERT and DELETE(s) ... can a stored procedure be run?

Solution:
The short answer is yes, the key thing is to know if the stored procedure is returning a result set or not as you have two tags available:

<sql:query> expects a ResultSet

<sql:update> does not expect a ResultSet - will throw an error if gets one. You do have access to an Integer result - eg rows updated.

For example, calling a stored procedure that returns a result set:


<sql:setDataSource var="myDataSource" dataSource="jdbc/myjndiref"/>
<sql:query var="examples" dataSource="${myDataSource}">
    exec ExampleProcLoadExample ?
    <sql:param value="${exampleId}"/>
</sql:query>
<c:choose>
    <c:when test="${fn:length(examples.rows) == 0}">
        <%-- no rows returned ! --%>
    </c:when>
    <c:otherwise>
        <c:set var="example" value="${examples.rows[0]}"/>
        <%-- got your object, can access columns with '.' notation --%>
    </c:otherwise>
</c:choose>

For example, calling a stored procedure that performs an 'update' (or insert/delete) returning number of rows updated:


<sql:setDataSource var="myDataSource" dataSource="jdbc/myjndiref"/>
<sql:update var="updateCount" dataSource="${myDataSource}">
    exec ExampleProcRemoveExample ?
    <sql:param value="${exampleId}"/>
</sql:update>
<c:choose>
    <c:when test="${updateCount le 0}">
        <%-- no rows updated ! --%>
    </c:when>
    <c:otherwise>
        <%-- some row(s) has been updated --%>
        <c:out value="${updateCount} row(s) have been updated"/>
    </c:otherwise>
</c:choose>

Notes:
When calling stored procedures you're getting into RDBMS vendor specific territory. Using the recommended JDBC drivers from the DB vendor for the DB version in use may make some of this work more smoothly.

Why can you not use a Wildcard as the first character in a Lucene search?

2008-02-27T15:54:00.003+11:00

Keywords:
apache lucene wildcard search index "why not" leading first

Problem:
Reading the Lucene query parser syntax documentation for their latest release, there's a line that says "Note: You cannot use a * or ? symbol as the first character of a search.".

Why not? Sure it may be inefficient, but what if you're willing to wear that. Is it something that is technically not possible, is it something that's up to users of the library to work around or will it eventually be implemented in Lucene?

Solution:
Out of curiosity for why this is a limitation I found notes in the Lucene Wiki that indicate that you can do it and it is possible.

Seems the Query Syntax guide in the Lucene release simply needs updating(?).


queryParser.setAllowLeadingWildcard(true);

Notes:
Note the Wiki says this feature is available as of 2.1. But it seems there was a bug in this release. I've tested this with lucene 2.3.1 and it works fine.

Generate is property set methods in JAXB objects

2007-10-31T10:58:00.000+11:00

Keywords:
JAXB "is property set" method object

Problem:
Defining a default value in the schema does not come through as a default value in the generated objects. This could be worked around if you could check for when a field has been explicitly set in the XML (as opposed the value being returned by the get or is) method being the default).

Solution:
Along the lines of past post - Getting xs:any as DOM object

You simply add another custom binding property:


<xs:appinfo>
    <jaxb:property generateIsSetMethod="true"/>
</xs:appinfo>

This post has the snippet: How do you pick up default values from XSD/JAXB
Reasonable summary of Customizing JAXB Bindings (though not that easy to read): Customizing JAXB Bindings.

Firefox does not animate my gifs

2007-08-24T17:13:00.000+10:00

Keywords:
firefox gif not animated

Problem:
Why is my animated gif working fine in IE but not firefox?

Solution:
The solution was on mozillaZine - I'm fairly sure I haven't turned image animation off explicitly, but to turn it on again:

Type about:config in the address bar

filter for "image.animation_mode"

if you're like me, you'll see this is set to "none". Change this to the default value of "normal".

Firefox does not reflect input form field values via innerHTML

2007-08-16T10:49:00.002+10:00

Keywords:
firefox innerHTML form input field value text select textarea

Problem:
In IE (and therefore the GWT test shell running on windows) you can call innerHTML on a DOM object and where it contains HTTP form input fields you will see an up-to-date reflection of the inputs from the user.

On firefox you simply get a reflection of the DOM as it was originally served up to the user.

This is a problem if you want to move HTML around and not loose the inputs already made by the user.

Eg: On clicking the button in firefox you won't see the input entered in the text box.


<form action="" method="get">       
    <SPAN id="MyContent">           
        <input type="text" name="textField" value="" /><br/>
    </SPAN>
</form>           
  
<button onClick="window.alert(MyContent.innerHTML);">discover user input</button>

Solution:
Found the solution on comp.lang.javascript - Firefox does not reflect selected option via innerHTML. I've extended the example code from this post to handle checkbox, radio and textarea ...

The idea is, every input field on the page must have an onBlur="updateDOM(this)" event handler, forcing the DOM to be updated and reflect the user's input.


<script type="text/javascript">
//
// Will be called by input fields when in 'update DOM' mode. This will
// make sure that changes to input fields in the form will be captured
// in the DOM - not necessary in IE but is required in Moz, etc as the DOM
// will otherwise reflect the page as it was initially.
//
// inputField : the input field that has just been tabbed out of (onBlur) OR the ID of the input field
function updateDOM(inputField) {
    // if the inputField ID string has been passed in, get the inputField object
    if (typeof inputField == "string") {
        inputField = document.getElementById(inputField);
    }
    
    if (inputField.type == "select-one") {
        for (var i=0; i<inputField.options.length; i++) {
            if (i == inputField.selectedIndex) {    
                inputField.options[inputField.selectedIndex].setAttribute("selected","selected");
            }
        }
    } else if (inputField.type == "select-multiple") {
        for (var i=0; i<inputField.options.length; i++) {
            if (inputField.options[i].selected) {
                inputField.options[i].setAttribute("selected","selected");
            } else {
                inputField.options[i].removeAttribute("selected");
            }
        }
    } else if (inputField.type == "text") {
        inputField.setAttribute("value",inputField.value);
    } else if (inputField.type == "textarea") {
        inputField.setAttribute("value",inputField.value);
        inputField.innerHTML = inputField.value;
    } else if (inputField.type == "checkbox") {
        if (inputField.checked) {
            inputField.setAttribute("checked","checked");
        } else {
            inputField.removeAttribute("checked");
        }
    } else if (inputField.type == "radio") {
        var radioNames = document.getElementsByName(inputField.name);
        for(var i=0; i < radioNames.length; i++) {
            if (radioNames[i].checked) {
                radioNames[i].setAttribute("checked","checked");
            } else {
                radioNames[i].removeAttribute("checked");
            }
        }
    }
}
</script>

<form action="" method="get">        
    <SPAN id="MyContent">            
        <input type="text" name="textField" value="" onBlur="updateDOM(this)"/><br/>
    </SPAN>
</form>            
    
<button onClick="window.alert(MyContent.innerHTML);">discover user input</button>

Notes:
It gets slightly trickier if you have input fields that don't get filled in by the user - eg a date picker dropdown, which will set the textbox with the date for the user, hence they never click in the box and trigger the 'onBlur'. In this case, you'd put the onBlur event on the date picker button

Eg:


<input type="text" name="dateField" id="dateField" value="" onBlur="updateDOM(this)"/>
<button id="myDatePicker" onClick="... do datepicking stuff ..." onBlur="updateDOM('dateField')">
 ... date picking image ...
</button>

Post updated (Thu, 25 Mar 2010): With thanks to the helpful commentors, the above script incorporates better handling for textArea & radio fields as well as an issue I came across for 'select-multiple' (was missing from the original script). It should work fine with the update via document or form approaches discussed in the comments - as opposed to the onBlur which continues to be good enough for my usage.

JAXB xs:any xml content missing from marshalled output

2007-07-20T13:22:00.000+10:00

Keywords:
JAXB xs:any xml content missing from marshalled output processContents="lax"

Problem:
I'm defining an XML schema that needs to be able to include any XML - "xs:any" seems perfect for the job. Also need to generate JAXB objects from this schema ... everything seems fine on compilation and in constructing the JAXB objects. The problem is at runtime, it appears that the "any" content is missing from the JAXB objects.

example schema

<xs:schema
    targetNamespace="http://example.com/xml"
    xmlns="http://example.com/xml"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:element name="MyXmlObject">
        <xs:complexType mixed="true">
            <xs:sequence minOccurs="0">
                <xs:any namespace="##any" processContents="lax" minOccurs="0"/>
            </xs:sequence>
            <xs:attribute name="firstName" type="xs:string" use="required"/>
            <xs:attribute name="lastName" type="xs:string" use="required"/>
            <xs:attribute name="happy" type="xs:boolean" use="optional"/>
        </xs:complexType>
    </xs:element>
</xs:schema>

example JAXB object usage

String xmlContent = "<foo>misc. text</foo>

";

InputSource source = new InputSource(new StringReader(xmlContent));
Element domElem = (Element)NodeUtils.parseStream(source, true);
myXmlObject.getContent().add(domElem);

JAXBContext jc = JAXBContext.newInstance("com.example.xml");
// marshal to System.out
Marshaller m = jc.createMarshaller();
m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
m.marshal( response, System.out);

example XML output (missing my any content)

<MyXmlObject xmlns="http://example.com/xml" firstName="bar" lastName="bar" happy="true">
</MyXmlObject>

Solution:
The JAXB 1.0.x FAQ had the answer - Can I access <xs:any> as a DOM node?. There's detailed notes here with links to example schema and the Bug report, but basically "the spec doesn't support the mapping to DOM, so the RI is not allowed to do this" ... but it will if you put it in "extension mode".

This involves adding some extra elements to your schema and compiling with the "-extension" switch (or extension="true" attribute if using the XJC ant task).

new example schema (with JAXB customisation)

<xs:schema
    targetNamespace="http://example.com/xml"
    xmlns="http://example.com/xml"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
    xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
    elementFormDefault="qualified"
    attributeFormDefault="unqualified"
    jaxb:extensionBindingPrefixes="xjc"
    jaxb:version="1.0">
    <xs:element name="MyXmlObject">
        <xs:complexType mixed="true">
            <xs:sequence minOccurs="0">
                <xs:any namespace="##any" processContents="lax" minOccurs="0">
                    <xs:annotation>
                        <xs:appinfo>
                            <xjc:dom/>
                        </xs:appinfo>
                    </xs:annotation>
                </xs:any>
            </xs:sequence>
            <xs:attribute name="firstName" type="xs:string" use="required"/>
            <xs:attribute name="lastName" type="xs:string" use="required"/>
            <xs:attribute name="happy" type="xs:boolean" use="optional"/>
        </xs:complexType>
    </xs:element>
</xs:schema>

NullPointerException tomcat5 realWriteChars

2007-07-18T10:55:00.000+10:00

Keywords:
NullPointerException tomcat5 realWriteChars servlet

Problem:
Getting this stack trace on each access of a servlet:


java.lang.NullPointerException
 at org.apache.coyote.tomcat5.OutputBuffer.realWriteChars(OutputBuffer.java:569)
 at org.apache.tomcat.util.buf.CharChunk.flushBuffer(CharChunk.java:435)
 at org.apache.tomcat.util.buf.CharChunk.append(CharChunk.java:366)
 at org.apache.coyote.tomcat5.OutputBuffer.write(OutputBuffer.java:516)
 at org.apache.coyote.tomcat5.CoyoteWriter.write(CoyoteWriter.java:149)
 at org.apache.coyote.tomcat5.CoyoteWriter.write(CoyoteWriter.java:158)
 at org.apache.coyote.tomcat5.CoyoteWriter.print(CoyoteWriter.java:208)
 at org.apache.coyote.tomcat5.CoyoteWriter.println(CoyoteWriter.java:265)
 at com.example.MyServlet.doGet(MyServlet.java:56)

The line number in "MyServlet" code that's kicking this off is a simple PrintWriter.println() ... what it's writing to the stream is definitely not null. How could a NPE be caused in tomcat?

Solution:
I wouldn't have guessed at the issue if not trying the same servlet on WebSphere ... then you get a more useful error message:
Invalid character encoding "UTF=8"

There's a typo (ie '=' instead of '-') in the call to set the content type on the HttpResponse object! Correcting this to "UTF-8" fixes the issue:
response.setContentType("text/html; charset=UTF-8");

IE ignores inline script added to DOM

2007-06-28T08:33:00.000+10:00

Keywords:
internet explorer GWT DHTML AJAX inline javascript "Object expected"

Problem:
I've got javascript code (GWT in this case) that adds an inline script to the DOM:


   <input ... onClick="myFunction()"/>
   <script type="text/javascript">
       function myFunction() {
           ... do stuff
       }
   </script>

If this code was on the page from the beginning, the event call to the function works fine. When this HTML is added to the page after it's loaded it appears the function call from the event fails.

IE Error (from the bottom left "! Done" in the status bar):


Line: 1
Char: 1
Error: Object expected

Further frustration - it works fine in Firefox.

Solution:
Aside: I haven't actually worked out why, but in GWT, if you use the method in a FlexTable setHTML the javascript will also not work in Firefox - you need to use setWidget(..).

Internet Explorer will not compile inline javascript code added to the DOM after the page has been loaded. What IE is trying to tell me in its cryptic error message is it's trying to call the function but can't find it.

Notes:
A good example of how to "smuggle" javascript into the DOM via img onLoad - Have Your DOM and Script It Too.

Avoid Copy & Paste with Ant MacroDef

2007-05-21T11:13:00.002+10:00

Keywords:
ant java copy paste macrodef gwt compile task

Problem:
There's no convenient ant task to allow you to compile (or re-compile) the GWT client files, but you can get some decent up-to-date check & compile behaviour going with a few lines of ant

... problem is, you need to duplicate these lines of code for every module in the project. It would be nice if you could modularise this.

Solution:
The Ant "macrodef" task lets you define a sequence of ant steps in a parameterised way and then call it any number of times with different parameters.

As can be seen in the example below (which handles 2 modules), adding a new module will require:

add a new entry to the "depends" list for gwt-generate (eg 'gwt-generate-newmod')
create a gwt-compile target 'gwt-generate-newmod' with an "unless" attribute of 'gwtGenerate.newmod.notRequired'
create a gwt-uptodate target to set the property 'gwtGenerate.newmod.notRequired' accordingly.

Yes, there's still some copy and paste, but you're just defining the module name and location rather that repeating the gwt-compile definition so there's less chance for a mistake.


<!-- this is the root target which will do all the generation (if required) -->
<target name="gwt-generate" description="Generate GWT code"
  depends="gwt-generate-common, gwt-generate-demo"/>

<target name="gwt-generate-common" depends="compile, gwt-check" unless="gwtGenerate.common.notRequired">
    <gwt-compile module="com.example.gwt.common.MyCommonModule"/>
</target>
<target name="gwt-generate-demo" depends="compile, gwt-check" unless="gwtGenerate.demo.notRequired">
    <gwt-compile module="com.example.gwt.demo.MyDemoModule"/>
</target>

<!-- this sets the *.notRequired properties if gwt code is uptodate -->
<target name="gwt-check">
  <!-- won't have any effect if the dirs are already there -->
  <mkdir dir="${build.home}/gwt"/>
  <mkdir dir="${build.home}/gwt/tmp"/>
  <mkdir dir="${build.home}/gwt/out"/>

    <gwt-uptodate property="gwtGenerate.common.notRequired"
            module="com.example.gwt.common.MyCommonModule"
            package="src/com/example/gwt/common"/>

    <gwt-uptodate property="gwtGenerate.demo.notRequired"
                    module="com.example.gwt.demo.MyDemoModule"
                    package="src/com/example/gwt/demo"/>          
</target>

<!-- this defines a macro task 'gwt-uptodate' -->
<macrodef name="gwt-uptodate" description="sets a property indicating if the module is up to date">
 <attribute name="property"/>
 <attribute name="module"/>
 <attribute name="package"/>
 <sequential>
         <!-- the module is uptodate if the .nocache.html is not older than any of the module src files -->
      <uptodate property="@{property}"
              targetfile="${build.home}/gwt/out/@{module}/@{module}.nocache.html">
          <srcfiles dir="@{package}" includes="**/*.*"/>
      </uptodate>                      
 </sequential>
</macrodef>  
<!-- this defines a macro task 'gwt-compile' -->
<macrodef name="gwt-compile" description="generates the GWT client code">
 <attribute name="module"/>
 <sequential>
         <!-- you must fork or it will fail -->
         <java dir="${build.home}/gwt/tmp" classname="com.google.gwt.dev.GWTCompiler" fork="true">
          <classpath>
              <!-- src directory containing module definition must be first! -->
              <pathelement location="src"/>
              <pathelement location="${build.home}/classes"/>
              <pathelement location="${gwt.user}"/>
              <pathelement location="${gwt.dev}"/>
              <pathelement location="${gwt.widgets}"/>
            </classpath>
          
          <sysproperty key="java.awt.headless" value="true"/>             
          <arg value="-out"/>
          <arg value="../out"/>
          <arg value="@{module}"/>  
      </java>
 </sequential>
</macrodef>

Notes:
Note, you only need to GWT-compile modules with an EntryPoint class in them. This is because it's only EntryPoint classes that you need to reference from your HTML and on compilation all the classes (and files in com.example.gwt.package/public!) are compiled/copied to this module. This means if you have multiple EntryPoint modules in your project (as I do) that reference a common Module, they will have their own compiled copy of this (and the /public files) rather than referencing it in a common location.

Note also, this means that the gwt-uptodate won't trigger a recompile if there's a change to a referenced module - as it's only checking the source folder containing the EntryPoint module ... so in those cases, you'll need to do a clean of the build folder containing generated source to guarantee everything is compiled up to date.

New Note: the sysproperty to set awt to headless is crucial on linux (if you're using ImageBundles). See Does the GWT 1.4 Compiler Need an X11 Window in Linux?

JavaMail Exception 550 relaying mail is not allowed

2007-05-07T12:13:00.000+10:00

Keywords:
JavaMail Exception 550 relaying mail to is not allowed

Problem:
Running server side code that sends an email is being rejected by the SMTP server:


javax.mail.SendFailedException: Invalid Addresses;
  nested exception is:
        com.sun.mail.smtp.SMTPAddressFailedException: 550 relaying mail to example.com is not allowed
        at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:1196)
        at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:584)
        at javax.mail.Transport.send0(Transport.java:169)
        at javax.mail.Transport.send(Transport.java:98)

Contrary to the error message, its not an issue isolated to the "To" recipient address. No matter what the "To" field was, the relay error was the same with the ???.com substituted in.

Other posts/support-resources on the web point to issues with authentication - but this SMTP server does not require authentication, just that the host is one of a set of IP addresses. Other web applications on the same host, running in the same (tomcat) application server are sending mail to this SMTP server with no problems.

Solution:
In this case, the difference was the spec of the JavaMail libraries. The apps that were working were all using spec 1.2 (deployed with activation.jar, mail.jar and mailapi.jar).

Our app getting the relay error was using spec 1.3 (implementation version 1.4). Downgrading the libraries (ie putting the 3 older jars in WEB-INF/lib) resolved the problem - no more errors from the SMTP server.

There may be a change in spec to do with the way the host is identified. If the libraries were identifying the client code's host as anything other than the IP address then this may be the problem. Perhaps the new libraries require additional properties to configure this behaviour? For the moment things are working but I may get to the bottom of this later ...

JSP EL expressions are being ignored by tomcat

2007-03-21T11:38:00.000+11:00

Keywords:
tomcat JSP JSTL EL

Problem:
Hopefully this is my last post about the possible problems with JSP/web-app specs and EL. In this case, there's a JSP using EL
Eg:


<%
    String myUrl = (String)session.getAttribute("SESSION_KEY_MY_URL");
    pageContext.setAttribute("myUrl", returnUrl);
%>
<form name="load" action="${myUrl}" method="GET">

It's coming out in HTML with the EL untouched (but the scriptlet is definitely being run).


<form name="load" action="${myUrl}" method="GET">

Why is the EL being ignored?

Solution:
As with the previous 2 posts on this issue, you have to fix the schema reference in the web.xml (there's too many differing copies of the web.xml(s) I'm dealing with here) and make sure the JSP has the right tablib uri reference - see this post.

For the first time I found this didn't immediately solve the problem! The HTML is coming out the same with EL unevaluated. The issue is that the JSP has been compiled to TOMCAT_HOME\work\Catalina\localhost\MyApp\org\apache\jsp\jsp\myfolder\MyJSP.java and tomcat sees no need to recompile even though I've updated the spec of the webapp.

The solution is to stop tomcat, remove the contents of TOMCAT_HOME\work and restart (OR update the timestamp on the JSP source file(s) to force recompilation). The JSP will be recompiled (to the right spec 2.0 now) and the EL will be evaluated as you expect.

How-to turn off tomcat session serialization

2007-03-20T12:03:00.000+11:00

Keywords:
tomcat session serialization NotSerializableException "Cannot serialize session attribute" Manager

Problem:
On restarting tomcat there's a stacktrace (below) about an attribute in the session not being serializable. It doesn't seem to effect the application starting up and the application works fine, but these messages at startup are annoying.

2007-03-20 10:50:57,890 INFO [org.apache.catalina.session.ManagerBase@898] - 
java.io.NotSerializableException: com.example.package.MyBeanClassName
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1054)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:278)
        at java.util.ArrayList.writeObject(ArrayList.java:531)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

If you want to put (transient) non-serializable objects in the session, how do you stop tomcat from serializing them at shutdown/startup?

Solution:
This was hard to find, but you need to configure a Manager in the context of the application. This should be put in either:

the YourApp.war:/META-INF/context.xml

the TOMCAT_HOME/conf/Catalina/localhost/YourApp.xml file

OR the default context ...

<!-- Turn off session serialization -->
    <Manager className="org.apache.catalina.session.PersistentManager"
      debug="0" distributable="false" saveOnRestart="false">
        <Store className="org.apache.catalina.session.FileStore"/>
    </Manager>

The tomcat documentation for the Manager element will give a bit more information, but it doesn't show the className for the file-store Store element, which is crucial if you're using the PersistentManager class - even if you're configuring it to do nothing!

You'll know it's working when there are no longer any files called "SESSIONS.ser" in the TOMCAT_HOME/work/Catalina/localhost/YourApp folder.

Can't get or find errorData attribute in JSP pageContext

2007-03-15T11:30:00.000+11:00

Keywords:
error JSP pageContext errorData scriplet

Problem:
Writing a JSP that handles errors from JSP, servlets (and other!) need to access the ErrorData object in a scriptlet rather that the convenient JSP EL ${pageContext.errorData}.

Tried:
pageContext.getAttribute("errorData"); but this returns null. Maybe it's not in the page scope.
pageContext.findAttribute("errorData"); but still null.

Solution:
Thankfully there's the convenience method:
pageContext.getErrorData();

This works. It seems the JSP EL ${pageContext.errorData} is a way of referencing this accessor rather than an element in the pageContext "map".

Structured data to GWT component with JSON

2007-03-14T14:12:00.000+11:00

Keywords:
GWT JSON stuctured initialisation data

Problem:
In a previous post I described using the internationalisation Dictionary class to pass in initialisation data. But what if the data is more complex than key-value pairs? You could define a dictionary value as being a delimited (e.g. space or comma separated) list of tokens but is there an easier way of getting in basic structured data without writing your own parser?

Solution:
JavaScript Object Notation (JSON) is a ".. text-based, human-readable format for representing objects and other data structures" (definition from wikipedia - the article includes a good introduction with examples). GWT supports reading and producing data in this format via the com.google.gwt.json.client package. For data interchange I think your still better off using a GWT remote service and sending your beans to it (let GWT handle the encoding/decoding) but for the host page giving data to the component JSON comes into its own.

Step 1

In the host page, define a dictionary as before but the value (or values) is/are now JSON strings rather than plain strings. In this example I'm creating an array of objects, each object having a property "id" and optionally a property "label" (it's got to be on one line as far as I can tell for the dictionary to allow it):

showHide: "[{\"id\": \"A\", \"label\": \"see A detail?\"}, {\"id\": \"B\", \"label\": \"include B detail?\"}, {\"id\": \"C\"}]"

Step 2

In the GWT component, use the dictionary to get at the JSON string. Then use the JSONParser to convert this to a JSON instance - in this example a JSONArray of JSONObjects. For a JSONObject you can get at each of its properties like you would a map via the get(String key) method.


public void onModuleLoad() {
    Dictionary properties = Dictionary.getDictionary("ModuleProperties");
  
    String showHideConfigString = properties.get("showHide");
    JSONArray showHideConfigs = (JSONArray)JSONParser.parse(showHideConfigString);
    
    List panels = new ArrayList();
    for (int i = 0; i < showHideConfigs.size(); i++) {
        JSONObject config = (JSONObject)showHideConfigs.get(i);
        
        JSONString idValue = (JSONString) config.get("id");
        String id = idValue.stringValue();
        
        JSONString labelValue = (JSONString) config.get("label");
        String label = (labelValue == null)? "include?" : labelValue.stringValue();
        
        // ... now we can do stuff with the data
        ShowHidePanel showHidePanel = new ShowHidePanel(label, id);
        RootPanel.get(id).add(showHidePanel);
        panels.add(showHidePanel);
    }
    
    // ... etc

Notes:
Someone asked me via comments how would you handle request parameters ... it's up to you to make something that can process the request parameters (CGI, java servlet, ASP?) and write a host page containing the data from the request params for the GWT component to then have access to them.

For many this will be obvious, but I felt bad for not including their comment ... but I don't want questions on the blog. Hope that helps.

If the data is more complex/rich than what JSON allows, there's XML.

org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported.

2007-02-28T11:40:00.000+11:00

Keywords:
Compile JSP tomcat JSTL error functions "org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported"

Problem:
Some fairly standard use of JSTL:
<c:out value="${fn:escapeXml(myvalue)}" />

i.e. using a function in the value field of the c:out tag gives the error:


org.apache.jasper.JasperException:
    <h3>Validation error messages from TagLibraryValidator for c</h3>
    <p>41: tag = 'out' / attribute = 'value': 
        An error occurred while parsing custom action attribute "value" with value "${fn:escapeXml(myvalue)}": 
            org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported.</p>

Solution:
It's the old mismatched spec issue again. Same solution as described in According to TLD or attribute directive in tag file, attribute X does not accept any expressions - namely, fix the schema reference in the web.xml and make sure the JSP has the right tablib uri reference.

GWT POST request doesn't include parameters

2007-01-23T15:18:00.001+11:00

Keywords:
GWT POST request parameters HTTP HTML RequestBuilder AJAX

Problem:
Following the GWT documentation for making a http-post but it's not clear what the post data should look like if you want it to include form parameters. The newer documentation for com.google.gwt.http.client has a bit more detail but the server side code processing the request (a java servlet) says there's no parameters in the request.

Solution:
It's not in the documentation, but if you want to post form data you must set the "Content-type" header value in the request to "application/x-www-form-urlencoded"

For Example:


StringBuffer postData = new StringBuffer();
// note param pairs are separated by a '&' 
// and each key-value pair is separated by a '='
postData.append(URL.encode("YourParameterName")).append("=").append(URL.encode("YourParameterValue"));
postData.append("&");
postData.append(URL.encode("YourParameterName2")).append("=").append(URL.encode("YourParameterValue2"));

RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, "/yourserver/formprocessor"));
builder.setHeader("Content-type", "application/x-www-form-urlencoded");
try {
  builder.sendRequest(postData.toString(), this /* or other RequestCallback impl*/);
} catch (RequestException e) {
  // handle this
}

Notes:
This sample chapter from the JavaScript™ Phrasebook is useful: Sending a POST Request

How to give initialisation parameters to a GWT component

2007-01-15T13:23:00.000+11:00

Keywords:
GWT init initialisation parameter dynamic config

Problem:
Where you have a servlet, JSP or other technology dynamically producing the HTML "host page" for a GWT component, it makes sense that you may want to parameterise the way the GWT component renders/behaves based on certain initialisation/input parameters.

How do pass parameters into the Module?

Solution:
There is a useful Dictionary facility in the Internationalisation (I18N) module ... it doesn't really have anything to do with Internationalisation but it's in this module because you could get the host page to provide key-to-locale-specific-message mappings to save the Module using any hard coded message text in a specific language.

It's generic enough that you could use it for any mapping of values.

The GWT documentation for Dictionary shows how to import the I18N module to your own module and then load the key-value mappings defined in the host page from your GWT code.

GWT shell resource not found *.nocache.html

2007-01-05T16:01:00.000+11:00

Keywords:
GWT AJAX shell resource not found nocache.html cache.html

Problem:
Following the Developer guide for making a GWT UI module. The code compiles fine with the GWT compiler and I now what to test and run using the GWT shell.

It starts up fine but I get the following error in the tree log of the shell when it opens up the HTML test page:


The development shell servlet received a request for
'com.example.gwt.mypackage.client.MyEntryPointClass.nocache.html'
in module 'com.example.gwt.mypackage.MyModuleName'

Solution:
My examplisation of the error message highlights what the problem was ...

The HTML "host page" must reference the module name in the meta tag, not the EntryPoint class or the ".client" package (it should be called .client if you want to use the GWT expectations for where things are). The module name is typically the package name parent of the ".client" package plus the name of the *.gwt.xml config file minus the extension.

Eg:
<meta name='gwt:module' content='com.example.gwt.MyModuleName'/>

JSTL TransformerFactoryImpl ClassCastException on WAS 6.0.2.11

2007-01-04T13:59:00.000+11:00

Keywords:
JSTL TransformerFactoryImpl ClassCastException WAS 6.0.2.11 xalan JAXP core xerces

Problem:
A web application that has the following properties:

includes the JAXP api jar files (in WEB-INF\lib)
deploys with the class loader properties of "Parent Last"
uses JSTL core

Will encounter the following stack trace from WAS when ever a JSP is loaded that contains JSTL (core reference):



JSP Processing Error
HTTP Error Code: 500
java.lang.ClassCastException: org.apache.xalan.processor.TransformerFactoryImpl
at javax.xml.transform.TransformerFactory.newInstance(Unknown Source)
at com.ibm.ws.jsp.translator.visitor.validator.PageDataImpl._getInputStream(PageDataImpl.java:125)
at com.ibm.ws.jsp.translator.visitor.validator.PageDataImpl.getInputStream(PageDataImpl.java:117)
at org.apache.taglibs.standard.tlv.JstlBaseTLV.validate(JstlBaseTLV.java:156)
at org.apache.taglibs.standard.tlv.JstlCoreTLV.validate(JstlCoreTLV.java:96)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.validateTagLib(ValidateVisitor.java:939)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.visitJspRootStart(ValidateVisitor.java:453)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.processJspElement(JspVisitor.java:124)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.visit(JspVisitor.java:110)
at com.ibm.ws.jsp.translator.JspTranslator.processVisitors(JspTranslator.java:121)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJsp(JspTranslatorUtil.java:168)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJspAndCompile(JspTranslatorUtil.java:81)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.translateJsp(JSPExtensionServletWrapper.java:360)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper._checkForTranslation(JSPExtensionServletWrapper.java:329)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.checkForTranslation(JSPExtensionServletWrapper.java:237)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.handleRequest(JSPExtensionServletWrapper.java:144)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3003)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:221)
at com.ibm.ws.webcontainer.VirtualHost.handleRequest(VirtualHost.java:210)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:1958)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:88)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:472)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:411)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:101)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.requestComplete(WorkQueueManager.java:566)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.attemptIO(WorkQueueManager.java:619)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.workerRun(WorkQueueManager.java:952)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager$Worker.run(WorkQueueManager.java:1039)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1470)

Solution:
In short, make sure the JSPs, JSTL refs and the web app are 2.4 compliant (see past post: What Spec?) and install the latest fix pack for WAS from IBM.

In detail, the following Problem ID is a different issue but underlying problem is the same - incorrect handling of loading XML & XSLT API classes for Parent Last apps - IBM - PK26233. The comment says it is resolved in the fix pack 6.0.2.15 for WebSphere Application Server, but I used 6.0.2.17 seeing it was newer - V6.0.2 Fix Pack 17.

According to TLD or attribute directive in tag file, attribute value does not accept any expressions

2006-12-12T12:24:00.002+11:00

Keywords:
Compile JSP tomcat JSTL error "According to TLD or attribute directive in tag file, attribute value does not accept any expressions"

Problem:
Compile error from tomcat when it encounters a JSP: "According to TLD or attribute directive in tag file, attribute value does not accept any expressions"

Solution:
For some reason the JSP is using the 1.2 JSP (and 1.0 JSTL) and EL expressions aren't understood. There's a lot of hits on the web for this but in summary there are 2 important things to do to ensure you're getting the right version of the spec:

Reference the correct servlet specification in your deployment descriptor:


<?xml version="1.0"?>
<web-app version="2.4"
 xmlns="http://java.sun.com/xml/ns/j2ee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

Reference the correct JSTL uri in your JSP:
change


<%@ taglib uri='http://java.sun.com/jstl/core' prefix='c'%>


<%@ taglib uri='http://java.sun.com/jsp/jstl/core' prefix='c'%>

Notes:

What Specification goes with what?
Web-app(deployment schema)	2.3	2.4	2.5
Web-app(deployment schema)	http://java.sun.com/dtd/web-app_2_3.dtd	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd
Servlet	2.3	2.4	2.5
JSP	1.2	2.0	2.1
JSTL(core uri reference)	1.0	1.1	1.2
JSTL(core uri reference)	http://java.sun.com/jstl/core	http://java.sun.com/jsp/jstl/core	http://java.sun.com/jsp/jstl/core
Tomcat	4.x	5.x	6.x
WebSphere	5.x	6.x	7.x (?)

WebSphere DTMConfigurationException: No default implementation found

2006-12-08T11:51:00.000+11:00

Keywords:
WebSphere DTMConfigurationException DTMManager xalan 6.0.2.11

Problem:After upgrading the WebSphere Application Server JDK with the .11 Fix pack (making it 6.0.2.11) there is the following error when my web app. tries to get a transformer:


org.apache.xml.dtm.DTMConfigurationException: No default implementation found
    at org.apache.xml.dtm.DTMManager.newInstance(DTMManager.java:177)
    at org.apache.xpath.XPathContext.(XPathContext.java:125)
    at org.apache.xalan.transformer.TransformerImpl.(TransformerImpl.java:398)
    at org.apache.xalan.templates.StylesheetRoot.newTransformer(StylesheetRoot.java:197)

Solution:
The problem seems to be at least associated with the fix pack creating a new file "xalan.properties" in APPSERVER_HOME\java\jre\lib. It could also be upgrading the xalan libraries as well (in xml.jar).

Edit this file - you'll notice this isn't defining any properties, everything is commented out - and add the property:
org.apache.xml.dtm.DTMManager=org.apache.xml.dtm.ref.DTMManagerDefault

Notes:
Alternatively, remove or rename this file and the problem should also go away.

Alternatively again, add the JVM system property "org.apache.xml.dtm.DTMManager". You can do this on WebSphere by going to:
Application servers > server1 > Process Definition > Java Virtual Machine
... and adding to the Generic JVM arguments:
-Dorg.apache.xml.dtm.DTMManager=org.apache.xml.dtm.ref.DTMManagerDefault

Restart the server and the problem should also go away - use this approach for where you don't have access to the APPSERVER_HOME\java\jre\lib files and can only configure your application's JVM.

IIS not streaming PDF

2006-11-15T16:53:00.000+11:00

Keywords:
IIS 6.0 not streaming PDF IE

Problem:
As is the theme for many of these posts. The setup is IIS -> ISAPI/JK -> Tomcat. The application running on Tomcat is generating PDF. If you access the application directly via Tomcat the PDF content is returned fine - ie. Opens via the Adobe Reader plugin in IE. If you access the application via IIS you get a blank page in IE. All other formats work fine.

Solution:
The problem in this case was a setting in IIS that zips the content it's serving up. This is fine for HTML as browsers recognise this and unzip. For the Adobe PDF reader, the content is not expected to be compressed - hence the blank page, it doesn't know what to do (but an error message would have helped).

In IIS Manager, right click on the folder "Web Sites" and choose Properties. Click the "Services" tab.

You need to make sure HTML Compression is turned off. I’m not sure about the IIS 5.0 isolation setting ...

Restart IIS – right click the server (above the Web Sites folder) and choose All Tasks > Restart IIS ...

Select the "Restart Internet Services on YOUR-SERVER" option. It will only take only a few seconds (rather than 300).

Can't start IIS "World Wide Web Publishing Service" Error 126

2006-11-14T09:44:00.000+11:00

Keywords:
Could not start IIS "World Wide Web Publishing Service" "Error 126"

Problem:
Trying to manually start the WWW service for IIS gives the following message:
"ERROR 126: The specified module could not be found."

The "World Wide Web Publishing Service" goes back to a stopped status. While this service is stopped, in the IIS Manager, the Web Sites folder is marked with an X and none of the Web Sites can be started.

Solution:
Need to check the Event Logs (Start > Programs > Administrative Tools > Event Viewer)

Clicking on the Application section shows a number of Errors. The most recent two errors were the most relevant:

Could not load all ISAPI filters for site/service. Therefore startup aborted.

The HTTP Filter DLL C:\[path to a DLL that no longer exists] failed to load. The data is the error.

I had to go into IIS Manager. View the ISAPI Filters (right click the Web Sites Folder > Properties > ISAPI Filters) and remove the filter that was referencing this DLL.

Going back to services, the WWW Publishing Service then starts fine.

spring webflow 1.0 build fails

2006-11-08T16:56:00.000+11:00

Keywords:
spring webflow 1.0 build sample

Problem:
Downloaded the latest spring webflow distribution (1.0) and trying to build (just a sample app. in this case) causes NoClassDefFoundError errors ... but surely this is shipped with the right libraries?

ivy.configure:
[echo] reading ivy config
[ivy:configure] :: Ivy 1.4 - 20061009124215 :: http://ivy.jayasoft.org/ ::

BUILD FAILED
java.lang.NoClassDefFoundError: org/apache/commons/httpclient/UsernamePasswordCredentials

Solution:
It's not enough to make sure you have Java 1.5+ and Ant 1.6+ ... these must also not have different versions of the dependent libraries.

In my case, there was an different version of apache commons-httpclient in the ant/lib folder ... removing this from the /lib folder or pointing at a 'clean' version of Ant resolves the issue.

java.io.FileNotFoundException spring-beans_2_0.dtd

2006-11-03T16:18:00.000+11:00

Keywords:
java.io.FileNotFoundException spring-beans_2_0.dtd spring java 2.0 MVC

Problem:
Following the guide (such as the "Spring Framework MVC application step-by-step") and you get this error about the DTD reference in the -servlet.xml file.

Solution:
This is an easy one, the file seems to have been renamed ... the DTD is actually accessed from the web. Change the _2_0 to -2.0


<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans_2_0.dtd">

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">

vmware "parent of this virtual disk could not be opened"

2006-09-13T10:37:00.000+10:00

Keywords:
vmware "parent of this virtual disk could not be opened" moved windows linux

Problem:
Moved a Virtual Machine setup (Windows 2003 Server RC2) that was created on a machine running Windows (2003 server) to a Linux machine (RedHat Enterprise 4) and get the following error when you try to view the the disk properties or start the Virtual Machine:

... "parent of this virtual disk could not be opened" ...

Solution:
If you've taken a snapshot for this VM in the past there will be a text file with a name like: "Windows Server 2003 Standard Edition-000001.vmdk". Stupidly, this contains a full path reference to the location of the "parent file" (which by default will be in the same folder). This has to be changed if you move the VM to another host machine.

Below is what this file looked like ... simply remove the full path reference, save the file and try again.


# Disk DescriptorFile
version=1
CID=e615c3de
parentCID=67e1d188
createType="twoGbMaxExtentSparse"
parentFileNameHint="c:\virtual machines\test-server\Windows Server 2003 Standard Edition.vmdk"
# Extent description
RW 4192256 SPARSE "Windows Server 2003 Standard Edition-000001-s001.vmdk"
RW 4192256 SPARSE "Windows Server 2003 Standard Edition-000001-s002.vmdk"
RW 4192256 SPARSE "Windows Server 2003 Standard Edition-000001-s003.vmdk"
RW 4192256 SPARSE "Windows Server 2003 Standard Edition-000001-s004.vmdk"
RW 8192 SPARSE "Windows Server 2003 Standard Edition-000001-s005.vmdk"

# The Disk Data Base
#DDB

Slide 2.1 working with Security on WebSphere 6.0.2.11

2006-07-26T14:16:00.000+10:00

Keywords:
slide 2.1 security websphere 6.0.2.11
Problem:
Slide 2.1 does not work "out-of-the-box" with WebSphere 6. It seems most slide-users have worked around it by turning off security. Clearly, this is not an option for a production system - so we need to get it working.
Solution:
This is a elaboration on my post #12099 to the slide-user list. Thanks to the post on the list from Lynn Richards #10690. A committer is welcome to add any content from here to the Slide-Wiki on WebSphere Setup. It certainly needs more detail. You will need:

slide-server-2.1 source code - in order to make corrections and re-build.

IBM HTTP Server (IHS) and the Web Server Plugin

Slide Source Changes - UTF-8

There are a two places (that I could find) in the code where the content type is set to "text/xml; charset=\"UTF-8\"". The WebSphere servlet container can't handle the quotes around the encoding. This needs to be changed to "text/xml; charset=UTF-8". This works for Tomcat too, so perhaps it should be committed in the server source?

jakarta-slide-server-src-2.1\src\webdav\server\org\apache\slide\webdav\method\AbstractWebdavMethod.java

128c128
< public static final String TEXT_XML_UTF_8 = "text/xml; charset=\"UTF-8\"";
---
> public static final String TEXT_XML_UTF_8 = "text/xml; charset=UTF-8";

jakarta-slide-server-src-2.1\src\webdav\server\org\apache\slide\webdav\util\DirectoryIndexGenerator.java

145c145

<         res.setContentType("text/html; charset=\"UTF-8\"");
---
>         res.setContentType("text/html; charset=UTF-8");

Slide Configuration

"/" Path "Forbidden"

The issue where all paths appear to be "/" no matter what path is accessed on Slide is due to the following code in jakarta-slide-server-src-2.1-\src\webdav\server\org\apache\slide\webdav\util\WebdavUtils.java and a difference in implementation between WebSphere and Tomcat

    String result = null;
  if (config.isDefaultServlet()) {
      result = req.getServletPath();
  } else {
      result = req.getPathInfo();
  }

req.getServletPath() seems to always be "/" in WebSphere when the WebDAV servlet is mapped to "/". The solution is to force slide to use the getPathInfo() method by turning off the Default Servlet flag in the web.xml:

 <param-name>default-servlet</param-name>
<param-value>false</param-value>

The EAR file might be corrupt? web.xml validation

When you install a war file on WebSphere the web.xml is parsed and validated against the spec. Any discrepancies with the spec will give you the un-helpful error that the "EAR file might be corrupt". Add the detail below to you opening node in the web.xml and make sure it is valid according to the schema (using an editor such as XML Spy) before including it in the war file:

<web-app
 version="2.4"
 xmlns="http://java.sun.com/xml/ns/j2ee";
 xsi="http://www.w3.org/2001/XMLSchema-instance"
 schemalocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

You'll find that all the <description> nodes are in the wrong place within the <init-param> nodes - they should be the first child rather than the last.
More importantly is the security-constraint section. To get authentication, you must define the constraint for all the possible http (WebDAV) methods. The problem is according to the web.xml spec, the only valid http-method values are: HEAD, GET, POST, PUT, DELETE, OPTIONS and TRACE. To have the other WebDAV methods secure as well, leave the specific http-method constraints out. This node is optional and if you don't specify any, all Http methods will be secure and this will include the WebDAV extensions too.

 <!-- Uncomment this to get authentication -->
<security-constraint>
  <web-resource-collection>
      <web-resource-name>DAV resource</web-resource-name>
      <url-pattern>/*</url-pattern>
      <!-- comment out the explicit http-method list                     
   'valid' Http Methods
         <http-method>GET</http-method>
         <http-method>HEAD</http-method>
         <http-method>OPTIONS</http-method>
         <http-method>POST</http-method>
         <http-method>PUT</http-method>
         <http-method>DELETE</http-method>
         Http Extensions
         <http-method>COPY</http-method>
         <http-method>LOCK</http-method>
         <http-method>MKCOL</http-method>
         <http-method>MOVE</http-method>
         <http-method>PROPFIND</http-method>
         <http-method>PROPPATCH</http-method>
         <http-method>UNLOCK</http-method>
         <http-method>VERSION-CONTROL</http-method>
         <http-method>REPORT</http-method>
         <http-method>CHECKIN</http-method>
         <http-method>CHECKOUT</http-method>
         <http-method>UNCHECKOUT</http-method>
         <http-method>MKWORKSPACE</http-method>
         <http-method>UPDATE</http-method>
         <http-method>LABEL</http-method>
         <http-method>MERGE</http-method>
         <http-method>BASELINE-CONTROL</http-method>
         <http-method>MKACTIVITY</http-method>
         <http-method>ACL</http-method>
         <http-method>SEARCH</http-method>
         <http-method>BIND</http-method>
         <http-method>UNBIND</http-method>
         <http-method>REBIND</http-method>
         <http-method>SUBSCRIBE</http-method>
         <http-method>UNSUBSCRIBE</http-method>
         <http-method>POLL</http-method>
         <http-method>NOTIFY</http-method>
  -->
  </web-resource-collection>
  <auth-constraint>
      <role-name>SlideAdmin</role-name>
      <role-name>User</role-name>
  </auth-constraint>
</security-constraint>

WebSphere Configuration

Global Security

How to configure WebSphere with a Custom or LDAP realm is beyond the scope of this post (maybe later) but with Security turned on, you will need to either Turn off "Java 2 Security" or define a policy file for the slide web-app.
With Java 2 security on, slide will get AccessControlException(s) when it tries to check for the existence of things like its properties file (from the "java.home" location? See Configuration.java - it will catch the exception if the load fails but not if the file.exists() check is forbidden).

WebServer Integration

It appears that when the WebSphere AppServer handles HTTP requests it assumes the same default as the IBM WebServer, namely - content is only to be expected and read for POST and PUT requests. This page on IBM's support site is old but seems to apply for v6 as well: Software
Group Ref #1145705.
To get the WebDAV extensions to HTTP working you need to configure the IBM WebServer with the AppServer using IBM's WebServer Plugin. It's in the Plugin where you're then able to allow content in all HTTP/WebDAV requests. Ie "true" for
AcceptAllContent
Specifies whether or not users can include content in POST, PUT, GET, and HEAD requests when a Content-Length or Transfer-encoding header is contained in the request header. You can specify one of the following values for this attribute:

true if content is to be expected and read for all requests
false if content only is only to be expected and read for POST and PUT requests.

false is the default.
If you have version 6, with the WebServer and AppServer on the same machine and the Server setup to propagate changes to the plugin-cfg.xml file, you can set this flag in the Admin Console:

Web servers > webserver1 > Plug-in properties > Request and response
Check the box for - Accept content for all requests

I found integrating the AppServer with the WebServer via plugin not a simple process. You should do this before installing slide and use the /snoop servlet to check if things are working via the WebServer.

Aside: If you try a URL like: http://localhost/snoop/hello/world/ok you will see the difference between the ServletPath and PathInfo in WebSphere and why we need to force slide to use the later.
You could actually use a WebServer other than IBM's. The difference will be that you may need to manually configure the Plugin in the AppServer and WebServer and then when the Admin console updates the plugin-cfg.xml file you may need to copy this to the place where the WebServer expects.

Installing Slide

After you install/deploy the slide.war (I gave it the enterprise application name of "slide") you need to edit the Class Loading properties.
Class loader mode = Parent Last
WAR class loader policy = Application
This avoids the problem of WebSphere v6 including an older version of JDOM (1.0Beta7) in its lib folder as well as property file loading issues. Check that slide has been correctly associated with the WebServer Plugin:

Enterprise Applications > slide > Map modules to servers
You should see something like:
Server
WebSphere:cell=wasNode01Cell,node=webserver1_node,server=webserver1
WebSphere:cell=wasNode01Cell,node=wasNode01,server=server1

It's important to see both the server and the webserver "module" in this list.
After starting the slide application it should be accessible via the WebServer (port 80 by default). All access will have to be via the WebServer and this should hopefully work without error and will be secure.

AccessControlException access denied WebSphere

2006-07-18T11:48:00.000+10:00

Keywords:
java.security.AccessControlException: access denied websphere

Problem:
After enabling global security in WebSphere, all access to file system resources from the web app gives "AccessControlException" messages. The application can't load it's properties file(s).

Solution:
I actually found this solution pretty quickly with a google search. Need to turn off "Java 2 Security" in the Global Security settings or define a policy that allows your application access to the resources it needs.

To disable "Java 2 Security"

Open the administrative console and go to Security-->Gloabal Security
Uncheck "Enforce Java 2 Security"
Save the changes and restart WebSphere

To define a policy

This is a little bit more complex, See: Configuring Java 2 security policy files

It may help to know how to grant everything
```
grant {
  java.security.AllPermissions;
}
```

Can't deploy WAR on WebSphere 6 - AppDeploymentException

2006-07-17T15:07:00.000+10:00

Keywords:
websphere war deploy install "The EAR file might be corrupt or incomplete" DeploymentDescriptorLoadException

Problem:
Trying to deploy ("install") a war file (for the Jakarta Slide WebDAV Server) in WebSphere after it appeared to work fine on Tomcat & JBoss gets the following two messages in the WebSphere Administration Console:

The EAR file might be corrupt or incomplete.

AppDeploymentException: [null] com.ibm.etools.j2ee.commonarchivecore.exception.DeploymentDescriptorLoadException: IWAE0022E Exception occurred loading deployment descriptor for module "[warfilename].war" in EAR file "[WebSphereHome]\profiles\[ProfileName]\wstemp\[TempFolder]\upload\[warfilename]_war.ear"

Solution:
The first message (and the .ear part of the second) is very confusing and from a quick google it seems that many developers are thrown off and attempt to put their war file in an ear ... it's not necessary.

The clue was the cause exception "DeploymentDescriptorLoadException" in the second message. It's a long story how I got to this, but the issue was my deployment descriptor - WEB-INF\web.xml. WebSphere validates this against the schema for the web.xml and is not flexible. Add this detail to you opening <web-app> node in your web.xml and make sure it is valid according to the schema (using an editor such as XML Spy):

<web-app version="2.4" 
xmlns="http://java.sun.com/xml/ns/j2ee"   
xsi="http://www.w3.org/2001/XMLSchema-instance" 
schemalocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

In my situation slide contained a security-constraint which in turn referenced http-method names that aren't valid according to the web.xml spec (limited to HEAD, GET, POST, PUT, DELETE, OPTIONS, TRACE). But WebDAV extends the HTTP spec ... not sure what to do about that. Commenting out the entire security-constraint section or the offending http-method references fixes the issue for the mean time.

Notes:
Next issue is how to configure some basic users and roles in WebSphere. The documentation seems very thorough on overviews and definitions, but light-on when it comes to how-tos.

Cannot load mod_jk.so into server: The specified procedure could not be found

2006-07-11T10:06:00.000+10:00

Keywords:
apache mod_jk mod_jk.so "The specified procedure could not be found" tomcat

Problem:
I've download the Apache HTTP server and according to the apache.org site "2.2.2 is the best available version". The downloaded mod_jk from the tomcat.apache.org where it claimed that the mod_jk-1.2.14-apache-2.0.54.so download was for Apache 2.0, and works with Apache 2.0.55 and later ... there was no 2.2.x download so I assumed (wrongly) that this would work with Apache 2.2.x as it is "later".

Added the LoadModule line in the httpd.conf file as instructed in http://tomcat.apache.org/connectors-doc/howto/apache.html
and got the following error:

Cannot load [full path]/mod_jk.so into server: The specified procedure could not be found

Solution:
You can't use a Apache 2.0.x module with Apache 2.2.x apparently - it must be built pointing at that specific version of Apache (if you're clever enough to build your own modules with the source code then this is no problem - you could get the source for JK 1.2.15 and build it pointing at your install Apache 2.2.x).

If you rely on the binaries built by Apache, use the HTTP server 2.0.x

xalan parameter must be a "valid Java Object"

2006-07-05T10:42:00.000+10:00

Keywords:
xalan IllegalArgumentException "The value of param" "must be a valid Java Object"

Problem:
On an application server (JBoss) where you can't control the version of xalan that is getting loaded with your web application, you get the following error in the preparation phase of a XML transform:


java.lang.IllegalArgumentException: The value of param [param-name] must be a valid Java Object
at org.apache.xalan.transformer.TransformerImpl.setParameter(TransformerImpl.java:1587)

Solution:
The issue here is that the object being set in the javax.xml.transform.Transformer.setParameter(String name, Object) is a null. In xalan 2.5.0 this doesn't seem to be an issue, but in xalan 2.7.0 it is!

Stop the null being put set as a parameter and the issue is solved.

Notes:
The last few posts have been around this issue of the web application not being able to control its classpath in JBoss. I've tried the ClassLoadingConfiguration advice in the JBoss Wiki with no success. The endorsed directory contains the different xalan library (as visible in the "sun.boot.class.path" system property) and despite specifying some sort of isolation, the endorsed directory still applies. As the issue was ultimately with a newer version of xalan and it's probably be bad to be putting nulls in anyway I haven't tried to force this class/library loading issue.

Invalid or corrupt jarfile

2006-07-03T10:25:00.000+10:00

Keywords:
"Invalid or corrupt jarfile" java -jar manifest file

Problem:
Packaging up a class with a main method into a jar-file using ant gives the following error when you try to run it with the java -jar [jarfile] command: "Invalid or corrupt jarfile".

Solution:
Using the ant task to create the manifest file on-the-fly gives you and entry like:


Manifest-Version: 1.0
Ant-Version: Apache Ant 1.6.2
Created-By: 1.4.2_07-b05 (Sun Microsystems Inc.)
Main-Class: com.example.MyMainClass

Creating the manifest file myself, with the bare essentials fixes the issue:


Manifest-Version: 1.0
Main-Class: com.example.MyMainClass

With more investigation I'm sure I could have got the dynamic meta-file creation working with Ant as I know other people do - there must be some peculiarity in the combination of my ant version (1.6.2), java version (1.4.2_07) and perhaps the current phase of the moon.

Notes:
Parsing of the Meta-inf file has been an issue that has come-up, been fixed and then come-up again for sun. See: Bug Id: 4991229. If you can work out if this bug exists in the your (or my) version of the Java SE you have more patience that me.

What version of xerces have I got?

2006-06-13T15:52:00.000+10:00

Keywords:
xerces version print classpath parser

Problem:
This is kind of related to the previous two posts. With XML parsing + classpath issues it's often useful to know not only what version of Xerces you're using but also where it's been loaded from.

Solution:
This is based on the equivalently useful site of Java Almanac - Determining from Where a Class Was Loaded. The point they make about the system classloader is crucial: "It is not possible to determine the location of classes loaded by the system class loader in the same way since the class' code source is null."

If your Xerces is the one loaded by the system, then this may explain some unusual behaviour if your web application expects to ship with it's own version.


  public static String getXercesDetails() {
       // no hard-writed references to the version class because it might be unavailable
       Class c;
       Method m;
       Object obj;

       try {
           c = Class.forName("org.apache.xerces.impl.Version");
           m = c.getDeclaredMethod("getVersion", new Class[] {});
           if (Modifier.isStatic(m.getModifiers())) {
               // Xerces 2.x
               obj = null;
           } else {
               // Xerces 2.1.x
               obj = c.newInstance();
           }
          
           ProtectionDomain pDomain = c.getProtectionDomain();
           CodeSource cSource = pDomain.getCodeSource();
           String loc = "?";
           if (cSource != null) {
               loc = cSource.getLocation().toString();
           } else {
               // CodeSource is null, Xerces loaded by system class loaded.
               loc = "(system classloader? sun.boot.class.path = " + System.getProperty("sun.boot.class.path") + ")";
           }
          
           return ((String) m.invoke(obj, new Object[] {})) + " from " + loc;
       } catch (Exception e) {
           return "unkown (" + e.getMessage() + ")";
       }
   }

Notes:
Xerces (and Xalan) in the endorsed directory can cause some nasty issues for applications that expect to use their own version. See the JBoss Issue: JBAS-2073

How do you print the java classpath?

2006-06-10T15:49:00.000+10:00

Keywords:
java servlet "print classpath"

Problem:
This requirement came in trying to diagnose the previous post. It'd be quite useful in a any enterprise/web application to be able to see the classpath in use (perhaps via an administration page).

Solution:
This is based on post on Java Tips (very useful site), but with the difference that your web application will have a different classloader to the system one. You'll need the classloader being used by a class within the web application (such as the one responsible for producing your admin-output).


 public String getClasspathString() {
     StringBuffer classpath = new StringBuffer();
     ClassLoader applicationClassLoader = this.getClass().getClassLoader();
     if (applicationClassLoader == null) {
         applicationClassLoader = ClassLoader.getSystemClassLoader();
     }
     URL[] urls = ((URLClassLoader)applicationClassLoader).getURLs();
      for(int i=0; i < urls.length; i++) {
          classpath.append(urls[i].getFile()).append("\r\n");
      }    
     
      return classpath.toString();
  }

An invalid XML character (Unicode: 0x0) was found in the comment

2006-06-09T15:48:00.000+10:00

Keywords:
xerces "An invalid XML character (Unicode: 0x0) was found in the comment"

Problem:
This is a very specific problem I admit, but what are you meant to do? From the error message list for the Xerces parser, it's clear that this "0x0" character is a bad thing, but it's also clear that I haven't put this character in the document.

Something's wrong with the reading/processing of the byte stream containing the XML content.

Solution:
A very specific solution too. In this case it was that file was being stored using a Slide implementation that came with JBoss. I don't know anything about this implementation, but it doesn't seem to work when you're accessing it (via WebDAV) with jakarta-slide-client libraries. Switching the storage to using the latest version from Jakarta fixed this issue.

shell script 'bad interpreter'

2006-04-10T16:25:00.000+10:00

Keywords:
tomcat catalina.sh "bad interpreter" sh shell

Problem:
Can't execute the shell script on linux. Everything seems in fine. The environment variables required by the script, the $PATH and the script has user has execute permission on the script (chmod +x catalina.sh).

Error each time is
bad interpreter: No such file or directory

Solution:
DOS/Non-Ascii characters in the script! Not sure vi doesn't highlight this (as ^M for example) - it could be a quirk with that version of vi or the console being used (putty in this case).

The solution is simple:
dos2unix catalina.sh catalina.sh

Try again via:
./catalina.sh run

All works.

Property/Variable reference in log4j.properties

2006-03-27T12:43:00.000+11:00

Keywords:
environment variable log4j.properties

Problem:
In your log4j.properties file a relative reference to a folder is fine as long as you start the program (eg tomcat) the same way from the same location every time.
Eg: log4j.appender.LOGGER.File=../logs/slide.log
(Ok if you're starting tomcat from CATALINA_HOME/bin/catalina.bat)

If not, you will get FileNotFound exceptions when the parent folder can't be found. In the above example, starting tomcat from a windows service will have the user.dir=C:\WINDOWS\SYSTEM32, so ../logs is C:\WINDOWS\logs & doesn't exist.

Solution:
Make explicit file references using system properties in the log4j.properties file. Note, you can not use environment variables (that's a platform specific concept).

System properties can be set in code or for this purpose should be set with the "-D" JVM option.

With the above tomcat example, most of the important environment variables to tomcat are copied into corresponding system properties if you use the standard scripts.
Eg: in catalina.bat: -Dcatalina.home=%CATALINA_HOME%

This allows you to reference the property using ${...} notation
Eg: log4j.appender.LOGGER.File=${catalina.home}/logs/slide.log

Missing JAAS Config

2006-03-26T12:30:00.000+11:00

Keywords:
"Unable to locate a login configuration" JAAS Tomcat

Problem:
Starting up tomcat as a service on Windows the above error message with stack trace displayed. The file it's referring to as missing is in the folder %CATALINA_HOME%/conf/jaas.config

Solution:
You need to make sure the system property "java.security.auth.login.config"
is defined & this should be a full path to the file. This can be via the -D JVM option. eg:
-Djava.security.auth.login.config=%CATALINA_BASE%\conf\jaas.config

Depending on whether you run tomcat via "catalina.bat" or the windows service will determine the best place to put this option.

Notes:
Ok, not a profound solution to start with but it's a solution with a problem description that will hopefully come up in a similar keyword search. I had to scroll to the 6th search result on http://www.google.com.au/search?hl=en&q=%22Unable+to+locate+a+login+configuration%22+JAAS+Tomcat
which actually isn't too bad.

Tired of googling questions with no answers

2006-03-20T18:15:00.000+11:00

As a Developer/Architect, questions are almost an everyday part of life. Particularly working with Java and Open Source technologies; limited documentation, weird stack traces, unexpected behaviour typically lead me to the web for help. I'm not alone ...

The typical sequence of problem solving goes as follows:

Putting question/error message/keywords in a web search.
This will almost always find results - in the hundreds & thousands - great!
Follow links to the search results and I'll find at least one if not dozens of descriptions of the exact same problem scenario.
Scroll down, follow the links to posted comments/replies. I'll find heaps of people saying they have the same problem ... but no solution. If I'm really unlucky, I'll find the last comment from the original poster saying "Oh forget it, I've resolved the issue ... thanks".
The wording/phrasing of someone's comment may lead me to thinking about my problem differently, inspire me to try something else and alleluia! The problem is solved and I move on the next one.

If I'm conscientious I'll note this in my trusty notebook for future reference. On the (very) rare occasion I'm feeling good will toward all people-kind I'll try to see if I can put at least my take on the solution on one of the websites I saw the exact same question. Inevitably they’ll only allow posts from "members" or the site will be an extract from some mailing list that I'm not on or that stopped existing months or even years ago. Then I go back to work.

The web is a great place for collaboration ... but I can't help but feeling that when it comes to the specific field of developer problems we're collaborating our questions very well but not the solutions.

Hence the Dev-Answers blog is born.

I really wouldn't expect people to read this regularly ... I expect this to be the longest post. My only hope is that if you search for a specific problem and end up being directed here, the specific solution (for me at least) will be here.

Comments are welcome as long as they add to the understanding of the problem/solution described. If you have a question use one of the various other forums to post it and then when you have an answer, post it here.

If no one uses this at all then at least it's an online version of my notebook ...

No Questions!