New to GWT, Google Code and App Engine - google-app-engine

Question

I am new in the whole Google code thing.
So my question is the following.
Having downloaded the Google Plugin for eclipse, i have created a new Project, which has automatically created an example code, the Greeting Example.
So I deployed it to the app Engine, an all worked OK. So now i am trying to add some functionality.. Via eclipse, I downloaded the Google Contacts API and transferred the Jars in the classpath as well as in the LIB directory.
So, in the server side of the project, in file GreetingServiceImpl.java I have added the following line
ContactsService contactsService = new ContactsService("Contacts");
so the file looks like this..
package com.gnt.server;
import com.gnt.client.GreetingService;
import com.gnt.shared.FieldVerifier;
import com.google.gdata.client.contacts.ContactsService;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
/**
* The server side implementation of the RPC service.
*/
#SuppressWarnings("serial")
public class GreetingServiceImpl extends RemoteServiceServlet implements
GreetingService {
public String greetServer(String input) throws IllegalArgumentException {
// Verify that the input is valid.
if (!FieldVerifier.isValidName(input)) {
// If the input is not valid, throw an IllegalArgumentException back to
// the client.
throw new IllegalArgumentException(
"Name must be at least 4 characters long");
}
String serverInfo = getServletContext().getServerInfo();
String userAgent = getThreadLocalRequest().getHeader("User-Agent");
// Escape data from the client to avoid cross-site script vulnerabilities.
input = escapeHtml(input);
userAgent = escapeHtml(userAgent);
ContactsService contactsService = new ContactsService("Contacts");
return "Hello, " + input + "!<br><br>I am running " + serverInfo
+ ".<br><br>It looks like you are using:<br>" + userAgent;
}
/**
* Escape an html string. Escaping data received from the client helps to
* prevent cross-site script vulnerabilities.
*
* #param html the html string to escape
* #return the escaped string
*/
private String escapeHtml(String html) {
if (html == null) {
return null;
}
return html.replaceAll("&", "&").replaceAll("<", "<")
.replaceAll(">", ">");
}
}
Now when i deploy this to the App Engine, i get the following error..
javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract java.lang.String com.gnt.client.GreetingService.greetServer(java.lang.String) throws java.lang.IllegalArgumentException' threw an unexpected exception: java.lang.NoClassDefFoundError: com/google/gdata/client/GoogleService
at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:385)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:588)
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:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:102)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:477)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.NoClassDefFoundError: com/google/gdata/client/GoogleService
at com.google.appengine.runtime.Request.process-ff033622b2cd8d3f(Request.java)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at com.gnt.server.GreetingServiceImpl.greetServer(GreetingServiceImpl.java:32)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:43)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:569)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
... 1 more
Caused by: java.lang.ClassNotFoundException: com.google.gdata.client.GoogleService
at com.google.appengine.runtime.Request.process-ff033622b2cd8d3f(Request.java)
... 34 more
How can this be; The necessary libraries are in the classpath and Lib directory...
I ve been searching for two days now and i have not found any answer...
For Testing purposes, i have added the Apache commons Lib and called a method from that lib and it worked perfectly inside the App Engine.
So what am i doing wrong? How can i use the Contacts API inside App Engine?
Thank you very much for your time!

Answer 1

You are probably missing the Google Data JARs.
See here for a tutorial. Make sure that gdata-client, gdata-client-meta, gdata-core, and gdata-media JARs are in your build path.