Failure to deploy on Google App Engine

I'm fairly inexperienced. I've been trying to get a Vaadin app to deploy to Google App Engine for almost a week, tried different configurations when creating the project in Eclipse and inside the web.xml file, but no matter what I do, I get the "500 error" in browser. I've chosen to create my app with Vaadin framework mostly for it's GAE functionality. I'm posting below the web.xml file and the errors on the GAE server log. The UI class has just the basic sample code with the button and the "thank you for clicking label", and I replaced the VaadinServlet class with GAEVaadinServlet. Please help!

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>proc</display-name>
 <servlet>
  <servlet-name>myservlet</servlet-name>
  <servlet-class>
    com.vaadin.server.GAEVaadinServlet
  </servlet-class>

  <init-param>
    <param-name>UI</param-name>
    <param-value>com.example.proc.ProcUI</param-value>
  </init-param>
</servlet>

<servlet-mapping>
  <servlet-name>myservlet</servlet-name>
  <url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>

GAE log:
 

W 18:50:57.456 EXCEPTION java.lang.ClassNotFoundException: com.vaadin.server.GAEVaadinServlet at 
com.google.appengine.runtime.Request.process-5857cfde810eba7e(Request.java) at java.lang.ClassLoader.loadClass(ClassLoader.java:375) 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.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437) at 
com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444) at 
com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300) at 
com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441) at java.lang.Thread.run(Thread.java:745) E 18:50:57.456 
javax.servlet.ServletContext log: unavailable javax.servlet.UnavailableException: com.vaadin.server.GAEVaadinServlet 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:206) at 
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:179) at 
com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:136) at 
com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:469) at 
com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437) at 
com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444) at 
com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300) at 
com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441) at 
com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:235) at java.lang.Thread.run(Thread.java:745) W 18:50:57.459 
Failed startup of context 
com.google.apphosting.utils.jetty.RuntimeAppEngineWebAppContext@1e89dbf{/,/base/data/home/apps/e~saptamanala/1.389771675399861701} 
java.lang.NullPointerException at java.lang.Class.isAssignableFrom(Native Method) at 
org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:256) at 
org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) at 
org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685) at 
org.mortbay.jetty.servlet.Context.startContext(Context.java:140) at 
org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250) at 
org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517) at 
org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467) at 
org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) at 
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:206) at 
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:179) at 
com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:136) at 
com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:469) at 
com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437) at 
com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444) at 
com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300) at 
com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441) at 
com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:235) at java.lang.Thread.run(Thread.java:745) F 18:50:57.530 
Uncaught exception from servlet java.lang.NullPointerException at java.lang.Class.isAssignableFrom(Native Method) at 
org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:256) at 
org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) at 
org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685) at 
org.mortbay.jetty.servlet.Context.startContext(Context.java:140) at 
org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250) at 
org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517) at 
org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467) at 
org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) at 
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:206) at 
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:179) at 
com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:136) at 
com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:469) at 
com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437) at 
com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444) at 
com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308) at 
com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300) at 
com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441) at 
com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:235) at java.lang.Thread.run(Thread.java:745)