Forwarding to a URL from Wicket

Sometimes we need to forward to a servlet or resource that’s outside of Wicket such as a servlet. Here’s how:

1. Modify your web.xml to define your servlet as well as your Wicket application “ignorePaths” init-param:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
 <display-name>Wicket Example</display-name>
 <filter>
 <filter-name>MyApplication</filter-name>
 <filter-class>org.apache.wicket.protocol.http.WicketFilter</filter-class>
 <init-param>
 <param-name>applicationClassName</param-name>
 <param-value>com.gu.MyApplication</param-value>
 </init-param>
 <init-param>
 <param-name>wicket.configuration</param-name>
 <param-value>deployment</param-value>
 </init-param>
 <init-param>
 <param-name>ignorePaths</param-name>
 <param-value>images/,s/</param-value>
 </init-param>
 </filter>
 <filter-mapping>
 <filter-name>MyApplication</filter-name>
 <url-pattern>/*</url-pattern>
 </filter-mapping>
 <servlet>
 <servlet-name>SomeServlet</servlet-name>
 <servlet-class>com.gu.SomeServlet</servlet-class>
 </servlet>
 <servlet-mapping>
 <servlet-name>SomeServlet</servlet-name>
 <url-pattern>/s/koolkat.do</url-pattern>
 </servlet-mapping>
</web-app>

The first observation is that Wicket is running as a Filter and not a Servlet. Second, the init-param – “ignorePaths” says that anything in the “/images” and “/s/*” will be ignored by Wicket Filter and passed along downstream.

2. Next in your Wicket Form, within your onSubmit method override you can do the following:

class TestForm extends Form(id){
  @override
  public TestForm(String id, SomeFormModel ghfm)
  {
    //Code removed
  }
  @override
  public onSubmit()
  {
    String url = "/s/koolkat.do"; //some url within the same web-context
    getRequestCycle().setRequestTarget(new RedirectRequestTarget(url));
  }
}

Notice that the url field does not contain the “ContextPath”. Wicket takes care of that in the background. On the other hand, suppose you wanted to redirect to a URL ourside of your web context or to an external site then you would set the variable like this.

String url = "http://mythinkpond.wordpress.com/2009/11/13/forwarding-to-a-url-from-wicket/";  //or
url = "http://myserver:port/othercontext/someurl";  

On some rare occasions, you might want to get the servlet Request Dispatcher to forward a request. For that it gets a little tricky.

– In your class you want to grab the “HttpServletResponse”. I’ve been unsuccessful in getting it in the class.

class xyz extends WebPage{
  public xyz()
  {
     HttpServletResponse response = getWebRequestCycle().getWebResponse().getHttpServletResponse();
     //additional code
     xyxForm thisForm = new xyzForm(thisModel, response);
  }
}

class xyzForm extends Form{
  HttpServletResponse response;

  public xyzForm(xyzModel model, HttpServletResponse thisResponse)
  {
     response = thisResponse;
  }
    
   public onSubmit() {
     HttpServletRequest request = getWebRequest().getHttpServletRequest();
     //additional code here
     getWebRequest().getHttpServletRequest().getRequestDispatcher(url).forward(request, response);
  }
}

Please note that the above code is pseudo-code and not actual code because I was writing it in Scala and not Java. But for the audience, I’m trying to express it in Java so that it can have the greatest impact.

That’s it! Happy Coding!

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