RESTful Web Services with Wicket

Here at ApacheCon, with the help of Jeremy Thomerson I could finally finish an idea I had months ago. How to easily provide simple RESTful Web Services with Wicket?

Basically, I wanted to output an Object as an XML with XStream. And the result is this simple class that you can extend and just have to provide a model with an object inside. Whatever is inside the model, gets outputted. :-)

So take a look at the class and use it as you wish.

package org.wicketstuff.wicketws;

import java.io.PrintWriter;

import org.apache.wicket.Component;
import org.apache.wicket.behavior.IBehavior;
import org.apache.wicket.markup.MarkupStream;
import org.apache.wicket.markup.html.WebPage;

import com.thoughtworks.xstream.XStream;

/**
 * RESTful WebSevice page
 */
public abstract class WebServicePage extends WebPage {

 private static final long serialVersionUID = 1L;

 public WebServicePage() {
  setStatelessHint(true);
 }

 protected final void onRender(MarkupStream markupStream) {
  PrintWriter pw = new PrintWriter(getResponse().getOutputStream());
  pw.write(getXML().toString());
  pw.close();
 }

 protected XStream createXStream() {
  XStream xstream = new XStream();
  xstream.setMode(XStream.ID_REFERENCES);
  return xstream;
 }

 private CharSequence getXML() {
  XStream xstream = createXStream();
  return xstream.toXML(getDefaultModelObject());
 }

 @Override
 public final String getMarkupType() {
  return "xml";
 }

 @Override
 public final boolean hasAssociatedMarkup() {
  return false;
 }

 @Override
 public final Component add(IBehavior... behaviors) {
  throw new UnsupportedOperationException(
    "WebServicePage does not support IBehaviours");
 }

}

And here's a quick example of a WebService:

package org.wicketstuff.wicketws;

import org.apache.wicket.PageParameters;
import org.apache.wicket.model.Model;

public class UserInfo extends WebServicePage {

 public UserInfo(PageParameters pg) {
  Integer id = pg.getAsInteger("id");
  if (id == null) {
   id = 1;
  }

  User user = ((WicketApplication) getApplication()).getUser(id);
  setDefaultModel(new Model(user));
 }

}

Oh, and don't forget to mount your WebService to get the default URL Strategy that is REST-like in Wicket.

 @Override
 protected void init() {
  mountBookmarkablePage("userInfo", UserInfo.class);
 }

Now all you have to do is access http://localhost:8080/myapp/userInfo/id/1

Done!! :D