Sekhar Vajjhala's Blog

Migrating WebLogic's JSP SimpleTag example to GlassFish

As I outlined in Migrate to GlassFish acitivities , I am migrating samples from different application servers to GlassFish to illustrate migration to GlassFish. Here, I selected the WebLogic's "JSP SimpleTag" sample to migrate to GlassFish.

Simple Tag Sample Application

The sample application that I migrated is the JSP Simple Tagsample from the WebLogic 9.2 distribution. The sample uses the Simple TAG API for iterating through a collection and accessing a database. I used the GlassFish + MySql bundle, resource injection, virtual directory mapping to migrate the application.

The source for the WebLogic sample is in the directory wls-install/weblogic92/samples/server/examples/src/examples/webapp/jsp/tags/simple.

To try the migrated sample to GlassFish

• Download and unzip gf_jspSimpleTagDir.zip . The directory gf_jspSimpleTag contains files in an exploded EAR format.
• Start MySql 5.0 database
• prepare database for example (see PointBase -> MySql section below)
• asadmin deploydir gf_jspSimpleTag
• http://localhost:8080/jspsimpleTag/SimpleTag.jsp

Deployment: WLS Split Directory -> GF Exploded Directory

This sample uses a split directory development structure. Thus, to deploy on GlassFish, I first generated a directory in exploded format using an ant build target in the build.xml for the WebLogic sample as follows:

• cd wls-install/weblogic92/samples/server/examples/src/webapp/jsp/tags/simple
• ant build
• ant package.exploded.ear

The above will build a jspSimpleTagEar directory in exploded format as shown below:

WebLogic: Exploded EAR
jspSimpleTagEar
   META-INF
   .. application.xml
   .. weblogic-application.xml
   jspSimpleTagWar
   .. ExamplesFooter.jsp
   .. ExamplesHeader.jsp
   .. SimpleTag.jsp
   .. wls_examples.css
   ++ WEB-INF
      .. web.xml
      .. weblogic.xml
      ++ classes/examples/webapp/jsp/tags/simple
         .. ExecuteSql.class
         .. IteratorTag.class
      ++ tlds
         .. simpleTag.tld

I repackaged the exploded directory as follows:

• Removed weblogic-application.xml. It was empty in this example.
• Replaced weblogic.xml with sun-web.xml. The mapping is described below.
• Modified simpleTag.jsp to use datasource name
• Modified ExecuteSql.java to use resource injection of DataSource.
• Modified ExamplesHeader.jsp to handle relative path in virtual directories.

Thus, the exploded ear on GlassFish is as follows:

GlassFish: Exploded EAR 
jspSimpleTagEar
   META-INF
   .. application.xml
   jspSimpleTagWar
   .. ExamplesFooter.jsp
   .. ExamplesHeader.jsp
   .. SimpleTag.jsp
   .. wls_examples.css
   ++ WEB-INF
      .. web.xml
      .. sun-web.xml
      ++ classes/examples/webapp/jsp/tags/simple
         .. ExecuteSql.class
         .. IteratorTag.class
      ++ tlds
         .. simpleTag.tld

Then I deployed the exploded directory gf_jspSimpleTag on GlassFish:

    asadmin deploydir gf_jspSimpleTag

PointBase -> MySql

The WebLogic sample uses PointBase database. While GlassFish does support PointBase, I chose to use MySql and used the GlassFish + MySql bundle which can be downloaded from http://java.sun.com/javaee/downloads/index.jsp. Next, I prepared the MySql database for the example - creating, configuring and populating.

Database name change

The WebLogic sample uses a database "examples-dataSource-demoXAPool". This step is not necessary but I wanted a more suitable name related to my migration work.

Create and Populate wls92examples database

Next, I created the wls92examples and populated it. To populate the script I used a script that came with the WebLogic sample. So here are the steps:

    $ cd gf-install/mysql/bin 
    $ mysql -u root
    mysql> create database wls92examples;
    mysql> grant all on wls92examples.* to 'sekhar'@'localhost' identified by 'secretpwd';
    mysql> quit
    $ mysql -u sekhar -p
    Enter password: secretepwd
    mysql> use wls92examples;
    mysql> source wls-install/weblogic92/samples/server/examples/src/examples/common/ddl/demo_mysql.ddl
    mysql> quit

Create a MySqlPool Connection Pool

Next, I created a new JDBC Connection Pool

• Name: MySqlPool
• Resource type: javax.sql.DataSource
• Datbase vendor: MySQL

I set the following properties using the GlassFish Admin Console. The properties can be set either when the MySqlPool connection pool is created or after pool creation by

• Navigate to: Resources -> Connection Pools -> MySqlPool
• Goto AdditionalProperties tab
• set the properties described below.

The properties that need to be set are:

• RelaxAutoCommit = true
  This property needs to be set to true since ExecuteSql class implements the following method from javax.servlet.jsp.tagext.TryCatchFinally interface:

       public void doCatch(Throwable t) throws Throwable {
           if (conn != null) conn.rollback();
           throw t;
       }
  

  The code makes an assumption that the autocommit is false. If autocommit is true, the above method will result in an exception ( logged to <gf-domain>/server.log file ):

       com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Can't call rollback when autocommit=true
  

• user, password properties
  Set the user and password used in creating and populating the "wls92examples" database.
• URL property
  Set the URL property to jdbc:mysql://:3306/wls92examples . This URL will be used to connect to the wls92examples database.

Create JDBC Resource jdbc/wls92examples

Create a JDBC Resource as follows:

• JNDI name : jdbc/wls92examples
• Pool name : MySqlPool ( created in above step )
• Description:

Source Code Changes

I modified the code as described here.

SimpleTag.jsp: Data source name change

Since I changed the database name to "wls92examples" (as described above), accordingly, I changed the datasource name accordingly here as well from

  // WebLogic
  String dataSourceName = "examples-dataSource-demoXAPool";

  // GlassFish
  String dataSourceName = "wls92examples;

ExecuteSql.java: Resource injection of DataSource

The ExecuteSql.java class establishes a connection to a database has non portable code

• use of weblogic.jndi.WLInitialContextFactory
• JNDI lookup on t3://localhost:7001

I wanted to make the code more portable. So I rewrote the code to use resource injection in Java EE 5.

    //File name: ExecuteSql.java 
    import javax.sql.DataSource;
    import javax.annotation.Resource;

    public class ExecuteSql extends BodyTagSupport implements TryCatchFinally { 
        ....
        @Resource(name="jdbc/wls92examples")
        DataSource wlsds;
        ... omitted other modifcations to code ...
    }

Resource injection works with managed classes. I was able to resource injection since ExceuteSql class is a managed class. ExecuteSql extends BodyTagSupport which in turn implements javax.servlet.jsp.tagext.Tag interface.

weblogic.xml -> sun-web.xml Mapping

I migrated the appserver specific deployment descriptor : weblogic to sun-web.xml as follows (Additional details ater the mapping).

  <!-- weblogic.xml -->

  <?xml version="1.0" encoding="ISO-8859-1"?>
  <weblogic-web-app xmlns="http://www.bea.com/ns/weblogic/90">
  <jsp-descriptor>
    <page-check-seconds>1</page-check-seconds>
    <verbose>true</verbose>
  </jsp-descriptor>
    <!--
  Use the virtual-directory-mapping element to specify document roots other
  than the default document root of the Web application for certain kinds of
  requests, such as image requests. All images for a set of Web applications
  can be stored in a single location, and need not be copied to the document
  root of each Web application that uses them. For an incoming request, if a
  virtual directory has been specified servlet container will search for the
  requested resource first in the virtual directory and then in the
  Web application's original document root.
  -->
  <virtual-directory-mapping>
    <local-path>C:/bea/weblogic92/samples/server/</local-path>
    <url-pattern>/examples/*</url-pattern>
  </virtual-directory-mapping>
  <virtual-directory-mapping>
    <local-path>C:/bea/weblogic92/samples/server/examples/build</local-path>
    <url-pattern>images/*</url-pattern>
  </virtual-directory-mapping>


  <!-- sun-web.xml -->
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE sun-web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Application Server 9.0 Servlet 2.5//EN" "http://www.sun.com/software/appserver/dtds/sun-web-app_2_5-0.dtd">
  <sun-web-app>
    <jsp-config>
      <property name="modificationTestInterval" value="1"/>
      <property name="verbose" value="true"/>
    </jsp-config>
    
    <property name="alternatedocroot_1" value="from=/examples/* dir=C:/bea/weblogic92/samples/server/"/>
    <property name="alternatedocroot_2" value="from=/images/* dir=C:/bea/weblogic92/samples/server/examples/build"/>
  </sun-web-app>

Virtual Directory Mapping

The example uses virtual directory mapping to locate the BEA logo in the example. The GlassFish equivalent for WebLogic's virtual-directory-mapping is the alternatedocroot property. I also had to make two more changes to bring up the BEA logo. Of course, I could have replaced it with a GlassFish logo once I was done :-) but I am trying to show migration issues here.

URL Pattern

In alternatedocroot_2, I changed the URL pattern from images/* to /images/*. Withtout the preceeding / , the following WARNING is generated in the GlassFish server.log file (i.e. gf-install/domain/domain1/logs/server.log )

    [#|2008-05-15T17:57:49.500-0400|WARNING|sun-appserver9.1|javax.enterprise.system.container.web|_ThreadID=24;_ThreadName=httpWorkerThread-4848-1;images/*;_RequestID=1b29dda8-9133-4863-b0ef-9b7ec44c8576;|WEB0504: URL pattern images/* for alternate docbase is invalid|#]

Relative Path in URL

Another issue I ran into was related to use of a relative path in ExamplesHeader.jsp. This file contains a reference to SRC using a relative path as shown in the following fragment.

<!-- weblogic : ExamplesHeader.jsp fragment -->
...

<!-- TITLE -->
<table border=0 cellspacing="18" cellpadding="0">
  <tr>
    <td valign="top">
      <a HREF="http://www.bea.com"><IMG SRC="../../../../images/logo_tm_onwt.jpg" alt="BEA Logo" width="161" height="96" border="0"></a>
      <h3><%=request.getParameter("title")%></h3>
    </td>
  </tr>
</table>
...

The relative path used for SRC did not work (the BEA logo won't come up). I changed the SRC reference to images/* .

<!-- GlassFish : ExamplesHeader.jsp fragment -->
...

<table border=0 cellspacing="18" cellpadding="0">
  <tr>
    <td valign="top">
      <a HREF="http://www.bea.com"><IMG SRC="images/logo_tm_onwt.jpg" alt="BEA Logo" width="161" height="96" border="0"></a>
      <h3><%=request.getParameter("title")%></h3>
    </td>
  </tr>
</table>
...

Summary

Except for the rewrite of the code to take advantage of resource injection for injecting a datasource, the code changes were minimal.

As always, feedback is welcome. For questions and feedback, visit Migrate To GlassFish project and follow the "Discussion Forums" link .

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