Weird 500 Error on GAE

i started getting this error on my app today, dont recall changing anything at all.. It works fine whenever i try it locally, but deployed i get this error.

EXCEPTION 
java.lang.ClassNotFoundException: se.myApp.server.MyServiceImpl
    at com.google.appengine.runtime.Request.process-bf332e9dcd56cd0b(Request.java)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at org.mortbay.util.Loader.loadClass(Loader.java:91)
    at org.mortbay.util.Loader.loadClass(Loader.java:71)
    at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:73)
    at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

E 2011-04-28 06:42:42.981

javax.servlet.ServletContext log: unavailable
javax.servlet.UnavailableException: se.myApp.server.MyServiceImpl
    at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:79)
    at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:191)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)


Failed startup of context com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@bd93cd{/,/base/data/home/apps/my_app/1.350039326756879872}
org.mortbay.util.MultiException[java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException, java.lang.NullPointerException]
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:656)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:191)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngine开发者_Python百科Adapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

Uncaught exception from servlet
javax.servlet.UnavailableException: Initialization failed.
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:200)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:168)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:123)
    at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:261)
    at com.google.apphosting.base.RuntimePb$EvaluationRuntime$2.handleRequest(RuntimePb.java:9285)
    at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:437)
    at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:573)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:448)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:688)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:326)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:318)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:446)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)

It is thrown whenever i perform a RPC-call from GWT, regardless os what RPC it may be. For example, calling getHello() will cause this error:

/**
 * The server side implementation of the RPC service.
 */
@SuppressWarnings("serial")
public class MyServiceImpl extends RemoteServiceServlet implements
        MyService {

    public String getHello()
    {
        return "Hello";
    }
}

web.xml looks like this,

<?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>
     <servlet>
    <servlet-name>myService</servlet-name>
    <servlet-class>se.myApp.server.MyServiceImpl</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>myService</servlet-name>
    <url-pattern>/etc/myService</url-pattern>
  </servlet-mapping>

  <!-- Default page to serve -->
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>

</web-app>

Update: After getting the lastest GAE SDK, GWT SDK: Tried deploying the standard GreetingSample to a new .appspot.com. The problem still persists there.

Update: After getting updates for eclipse the error seems to have gone away, HOWEVER, everytime there is one tiny error in the server-side code, lets say a miss-spelled query, instead of throwing a normal error pointing to the query, i get the above error instead.

This has happened me a few times when doing rapid deployments from my IDE while testing.

You probably have a partially deployed app.

You should do a rollback on the app to make sure it isn't partially deployed and then do a redeploy.

I stopped having these problems when I Mavenized my project and started using the maven-gae-plugin to do deployments.

It makes deployment as simple as mvn clean package gae:deploy. It also makes doing roll backs as simple as mvn gae:rollback

I have instructions on setting up Maven 3 for GAE deployment, it does include GWT support as well, you can remove that if you are not using GWT.