Resolver.class && Collection Nulls

[Brandon Donnelson]

The Resolver.class is fragile to null list exceptions. 

Workaround is, be sure no null list gets passed to client.

How to find the the offending list:

http://codintips.blogspot.com/2012/05/pausing-on-all-null-exceptions-in.html

java.lang.NullPointerException
        at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:618)
        at com.google.web.bindery.requestfactory.server.Resolver.access$400(Resolver.java:50)
        at com.google.web.bindery.requestfactory.server.Resolver$PropertyResolver.visitReferenceProperty(Resolver.java:139)
        at com.google.web.bindery.autobean.shared.AutoBeanVisitor.visitCollectionProperty(AutoBeanVisitor.java:229)
        at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:300)
        at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166)
        at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101)
        at com.google.web.bindery.requestfactory.server.Resolver.resolveClientValue(Resolver.java:395)
        at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.processInvocationMessages(SimpleRequestProcessor.java:483)
        at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:225)
        at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:127)
        at com.google.web.bindery.requestfactory.server.RequestFactoryServlet.doPost(RequestFactoryServlet.java:133)
        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)

Brandon Donnelson

http://c.gwt-examples.com

[Brandon Donnelson]

It was a null value in the list and not the list being null it self.

That is the is:

[true, null, null, null, null, null, null, null, null, null, null, null, null] => com.google.web.bindery.requestfactory.server.Resolver$CollectionType@b1a0121a

[Brandon Donnelson]

Screenshot of the null event. :)

[Brandon Donnelson]

Issues for it: http://code.google.com/p/google-web-toolkit/issues/detail?id=6809

Seems I ran across it again.