title: GWT - RPC SerializationException
body: <p>It's been a while since I've been doing GWT and I needed something small done quickly. I set things up and now I have a RPC I need, but it fails.</p>
  
  <p>The RPC is supposed to give me a ArrayList, and Vacancy is located in #projectname#.client.model. 
  The call is made in #projectname#.client.model.
  <br />
  The interfaces for my Services are in #project#name.client.Service.
  <br />
  Finally, the calls of course go to #projectname#.server.
  <br />
  Vacancy implements IsSerializable. The Exception I get from running my RPC is the following:</p>
  
  <pre><code>Starting Jetty on port 8888
  [WARN] Exception while dispatching incoming RPC call
  com.google.gwt.user.client.rpc.SerializationException: Type 'firsteight.client.model.Vacancy' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized.: instance = firsteight.client.model.Vacancy@15fdd2f
      at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:619)
      at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
      at com.google.gwt.user.client.rpc.core.java.util.Collection_CustomFieldSerializerBase.serialize(Collection_CustomFieldSerializerBase.java:44)
      at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serialize(ArrayList_CustomFieldSerializer.java:39)
      at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:51)
      at com.google.gwt.user.client.rpc.core.java.util.ArrayList_CustomFieldSerializer.serializeInstance(ArrayList_CustomFieldSerializer.java:28)
      at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:740)
      at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:621)
      at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamWriter.writeObject(AbstractSerializationStreamWriter.java:126)
      at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter$ValueWriter$8.write(ServerSerializationStreamWriter.java:153)
      at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeValue(ServerSerializationStreamWriter.java:539)
      at com.google.gwt.user.server.rpc.RPC.encodeResponse(RPC.java:616)
      at com.google.gwt.user.server.rpc.RPC.encodeResponseForSuccess(RPC.java:474)
      at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:571)
      at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
      at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
      at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
      at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
      at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
      at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
      at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
      at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
      at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
      at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
      at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
      at org.mortbay.jetty.Server.handle(Server.java:324)
      at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
      at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843)
      at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647)
      at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
      at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
      at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
      at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)
  </code></pre>
  
  <p>The RPC I make is the following:</p>
  
  <pre><code>void getVacs() {
      try {
          homeService.getVacancies(new AsyncCallback&lt;ArrayList&lt;Vacancy&gt;&gt;() {
              public void onFailure(Throwable caught)
              {
                  RootPanel.get("grayblock").add(new HTML("Failed:" + caught.getMessage()));
              }
  
              public void onSuccess(ArrayList&lt;Vacancy&gt; result)
              {
                  RootPanel.get("grayblock").add(new HTML(result.get(0).getTitle()));
              }
          });
      } catch (IllegalArgumentException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  }
  </code></pre>
  
  <p>I thought I had done all I needed to make Vacancy Serializable, and an ArrayList of Vacancy as returntype for the RPC counts as having Vacancy as return type.. right? What am I doing wrong?</p>
  
  <p>Thanks in advance!</p>