Hello,
I’ve created Google app engine / Vaadin HelloWorld application step-by-step using
HOW-TO
s. Application was crashing and it takes me all day to find out why. Here is my report. I was not able to find solution on web, so I hope this will help someone.
Tomcat Application log:
V 05, 2012 7:26:37 ODP. com.vaadin.terminal.gwt.server.GAEApplicationServlet service
WARNING: An exception occurred while servicing request.
java.lang.NullPointerException
at com.google.appengine.api.NamespaceManager.get(NamespaceManager.java:109)
at com.google.appengine.api.memcache.BaseMemcacheServiceImpl.getEffectiveNamespace(BaseMemcacheServiceImpl.java:68)
at com.google.appengine.api.memcache.AsyncMemcacheServiceImpl.doPut(AsyncMemcacheServiceImpl.java:394)
at com.google.appengine.api.memcache.AsyncMemcacheServiceImpl.put(AsyncMemcacheServiceImpl.java:448)
at com.google.appengine.api.memcache.MemcacheServiceImpl.put(MemcacheServiceImpl.java:71)
at com.vaadin.terminal.gwt.server.GAEApplicationServlet.service(GAEApplicationServlet.java:216)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
It failed on tomcat but deploy to Google App Engine was okay… I tried everything (debugging, decompiling, another versions of tomcat, vaadin, appengine, libraries…)
Solution:
Edit
war/WEB-INF/web.xml
to
ApplicationServlet
instead of
GAEApplicationServlet
.
Yes, I found it is in that how-to mentioned, I’ve missed it. My bad. 
Cheers,
Milan