Struts 2 Portlet in WebSphere 5.1

At work I recently wanted to build a Struts 2 Portlet to see if I could deploy it in WebSphere Portal 5.1. As you know, Struts 2 requires Java 5 to run, and as you might also know, WebSphere Portal 5.1 only runs Java 1.4. Retrotranslator to the rescue! I added the retrotranslator-maven-plugin from the Codehaus Mojo project, and set it up to run the translate-war goal:

<build>
  <plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>retrotranslator-maven-plugin</artifactId>
    <version>1.0-alpha-2</version>
    <executions>
      <execution>
        <goals>
          <goal>translate-war</goal>
        </goals>
        <configuration>
        <classifier>jdk1.4</classifier>
        <attach>true</attach>
          <advanced>true</advanced>
        </configuration>
      </execution>
    </executions>
  </plugin>
</build>

I also had to include a couple of new dependencies introduced by Retrotranslator:

<dependencies>
  <dependency>
    <groupId>backport-util-concurrent</groupId>
    <artifactId>backport-util-concurrent</artifactId>
    <version>3.0</version>
  </dependency>
  <dependency>
    <groupId>net.sf.retrotranslator</groupId>
    <artifactId>retrotranslator-runtime</artifactId>
    <version>1.2.1</version>
  </dependency>
</dependencies>

I had to use the 1.0-alpha-2 version of the plugin, otherwise I got an obscure java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Boolean failure...

Unfortunately, that was not quite enough. When running the portlet, I would get an exception about a missing javax.xml.namespace.NamespaceContext class which XWork aparently needs. It appears that this class is included in the Java 5 libraries, but not with Java 1.4. I found it in the jaxp-api.jar in the Sun Java Web Services Developer Pack 2.0. I placed this jar in the %WAS_HOME%/java/jre/lib/ext folder (I tried putting it in the web application, but that didn't work... Classloading in JEE application servers has always been fun...). I also had to exclude any web application dependencies that included Xerces, Xalan or xml-apis.

No guarantees that this works for you though. But I guess as long as you don't break any of the limitations retrotranslator has, you'll be fine.