gwt java.lang.ExceptionInInitializerError - exception

Question

I'm working on a GWT app, and keep getting the error shown below.
I followed the GWT tutorial regarding naming conventions for servlet classes, and followed the Service / Async / ServiceImpl structure.
I also tried adding the -XX:-UseSplitVerifier VM argument to fix a previous problem. any ideas on what's going on?
SEVERE: javax.servlet.ServletContext log: Exception while dispatching incoming RPC
call
java.lang.ExceptionInInitializerError
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at
com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_
(Runtime.java:127)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance
(Runtime.java:135)
at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.instantiate
(ServerSerializationStreamReader.java:914)
at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserialize
(ServerSerializationStreamReader.java:556)
at com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject
(AbstractSerializationStreamReader.java:119)
at
com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader$ValueReader$8.
readValue(ServerSerializationStreamReader.java:138)
at
com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserializeValue
(ServerSerializationStreamReader.java:385)
at com.google.gwt.user.server.rpc.RPC.decodeRequest(RPC.java:303)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall
(RemoteServiceServlet.java:206)
at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost
(RemoteServiceServlet.java:248)
at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost
(AbstractRemoteServiceServlet.java:62)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1166)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter
(HeaderVerificationFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter
(ServeBlobFilter.java:60)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter
(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter
(StaticFileFilter.java:122)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1157)
at com.google.appengine.tools.development.BackendServersFilter.doFilter
(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle
(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle
(DevAppEngineWebAppContext.java:78)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at
com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle
(JettyContainerService.java:369)
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$RequestHandler.content(HttpConnection.java:938)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.lang.UnsupportedOperationException: ERROR: GWT.create() is only usable
in client code! It cannot be called, for example, from server code. If you are
running a unit test, check that your test case extends GWTTestCase and that
GWT.create() is not called from within an initializer or constructor.
at com.google.gwt.core.client.GWT.create(GWT.java:91)
at com.google.gwt.user.client.ui.UIObject.<clinit>(UIObject.java:187)
... 46 more

Answer 1

Almost for sure you are calling a class that is GWT client only. You have the error:
Caused by: java.lang.UnsupportedOperationException: ERROR: GWT.create() is only usable
in client code! It cannot be called, for example, from server code. If you are
running a unit test, check that your test case extends GWTTestCase and that
GWT.create() is not called from within an initializer or constructor.
You don't need to specifically call "GWT.create()" yourself to get that exception. you might be calling a GWT client only class on the server side. Also you might containg a "client only" object in one of your RPC's arguments or even on shared code being called on the server side.

Answer 2

FWIW, I had the same error and it ended up being a constant (static final) that used GWT.create() to initialise. The constant was in a class that needed to be loaded by the GIN dependency injection parser.
IE: It was trying to load the class (and call GWT.create()) during module compile.