Creating hierarchical actions in struts 2.1

Struts 2.1 doesn't directly support hierarchical actions. Nonetheless I still was able to implement them at visualmandarin.
Notice how the podcasts and exercises urls are all organized into folders and even the lesson title is present in the url: Lesson - Can I have a menu please?

If you are interested in SEO optimized urls for your website this kind of feature is a MUST. But how to do it struts 2.1? In short the steps you need to follow are:

Step 1

If you are running on struts 2, migrate to struts 2.1

Step 2

Make sure you are using the convention plugin

Step 3

Ensure that all your actions have an explicit namespace. If you don't you might find that those actions are being called when they shouldn't.

Step 4

Create a wildcard action in the namespace that you want to be hierarchical. In my case I have created one in namespace /lessons:

<action name="*" namespace="/lessons" method="execute" class="lessonsLocator">
<result name="lister"></result>
<result name="ResourceNotFoundException" type="chain">404</result>
</action>

Your lessons locator action should inspect the uri to determine which resource to display. In my case I was dealing with lessons but you could be dealing with categories and products or anything else. It shouldn't make any difference.

Step 5

Extend org.struts2.impl.StrutsActionProxy and override the following prepare() method:

@Override
  protected void prepare() {
      String profileKey = "create DefaultActionProxy: ";
      try {
          UtilTimerStack.push(profileKey);
          // we backtrack the namespace until we find an action that matches
          this.findActionByBacktracking();
        
          if (config == null && unknownHandler != null) {
              config = unknownHandler.handleUnknownAction(namespace, actionName);
          }
          if (config == null) {
              String message;

              if ((namespace != null) && (namespace.trim().length() > 0)) {
                  message = LocalizedTextUtil.findDefaultText(XWorkMessages.MISSING_PACKAGE_ACTION_EXCEPTION, Locale.getDefault(), new String[]{
                      namespace, actionName
                  });
              } else {
                  message = LocalizedTextUtil.findDefaultText(XWorkMessages.MISSING_ACTION_EXCEPTION, Locale.getDefault(), new String[]{
                      actionName
                  });
              }
              throw new ConfigurationException(message);
          }

          resolveMethod();
        
          if (!config.isAllowedMethod(method)) {
              throw new ConfigurationException("Invalid method: "+method+" for action "+actionName);
          }

          invocation.init(this);

      } finally {
          UtilTimerStack.pop(profileKey);
      }
   }

  /**
   * Returns a list of all possible namespaces. The one with biggest length
   * is top of the list up to /xxx... bottom of a list. Note that we don't backtrack until
   * the empty namespace
   *
   * @param namespace
   * @return
   */
  private String [] getAllPossibleNamespaces(String namespace) {
   List<String> namespaces = new ArrayList<String>();
   // e.g. /lessons/hsk/.../1 ->
   String [] tokens = namespace.split("/");
   tokens=removeEmptyStrings(tokens);
   if (tokens != null && tokens.length >= 0) {
    for (int i=0; i< tokens.length; i ++) {
     String gnamespace="";
     for (int j=0;j<tokens.length- i;j++) {
      gnamespace += "/" + tokens[j] ;
     }
     namespaces.add(gnamespace);
    }
   }
   return namespaces.toArray(new String[0]);
  }

  private String [] removeEmptyStrings(String [] tokens) {
   List<String> result = new ArrayList();
   for (String token: tokens) {
    if (token == null || token.equals("")) {
   
    }
    else {
     result.add(token);
    }
   }
   return result.toArray(new String[0]);
  }

  /**
    * Searches for the given action in one or more namespaces
    *
    */
  private void findActionByBacktracking() {
   if (namespace != null && !namespace.equals("") && !namespace.equals("/")) {
    String [] namespaces =this.getAllPossibleNamespaces(namespace);
  
    for (String namespace: namespaces) {
   
        config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);

        if (config != null ) break;
    }
 
   }
   else {
       config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);    
   }
 
  }

Step 6

Extend org.apache.struts2.impl.StrutsActionProxyFactory.

My implementation as an example:

public class HierarchicalActionProxyFactory extends DefaultActionProxyFactory {
  @Override
  public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {
    
      HierarchicalActionProxy proxy = new HierarchicalActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
      container.inject(proxy);
      proxy.prepare();
      return proxy;
  }
}

Step 7

Finally the last step: override the property struts.actionProxyFactory
in struts.properties and point to your implementation of the proxy factory.

My implementation was:

struts.actionProxyFactory=com.visualmandarin.web.config.HierarchicalActionProxyFactory

If you have followed these steps correctly you should be able to have the same kind of urls that I have in visualmandarin.com website. If there's something that you don't understand don't hesitate to ask!

You can find a working example here. This war file was tested in jboss 4.2.3 but should work in any compliant application server.

What you need to get this example working:

• Add the struts 2 library files to the lib directory


• Add the convention plugin jar file to the lib directory


• Specify the correct path to your application server

Once you build the war file and deploy it, you can access the example at http://localhost/example3 or http://localhost:8080/example3