Hi, I have following object child relationship. All the objects are getting saved properly but when I try to fetch child object I am getting NullPointerException. This error is not because of lazy loading as I am accessing the child before closing the PersistentManager. Aren't interfaces fully supported by JOD?
============ Parent Object Class ============== @PersistenceCapable(identityType = IdentityType.APPLICATION) public class Block implements Serializable { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Long block_id; @Persistent(defaultFetchGroup = "true") private BlockModule block_module; .... .... ============= Child Interface and Implementation ============ public interface BlockModule extends Serializable{ String getTitle(HttpServletRequest req); String getContent(HttpServletRequest req); } @PersistenceCapable(identityType = IdentityType.APPLICATION) public class BlockTextHTML implements BlockModule{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) protected Key key; @Persistent private String block_title; @Persistent(types = {BlockTextHTML.class}) private String block_content; .... .... ================= ERROR LOG ================ Uncaught exception from servlet java.lang.NullPointerException at org.datanucleus.store.mapped.identifier.JPOXIdentifierFactory.newDatastoreContainerIdentifier(JPOXIdentifierFactory.java:258) at org.datanucleus.store.appengine.DatastoreRelationFieldManager.lookupOneToOneChild(DatastoreRelationFieldManager.java:316) at org.datanucleus.store.appengine.DatastoreRelationFieldManager.fetchRelationField(DatastoreRelationFieldManager.java:286) at org.datanucleus.store.appengine.DatastoreFieldManager.fetchObjectField(DatastoreFieldManager.java:271) at org.datanucleus.state.AbstractStateManager.replacingObjectField(AbstractStateManager.java:1197) at antshpra.Block.jdoReplaceField(Block.java) at antshpra.Block.jdoReplaceFields(Block.java) at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2772) at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2791) at org.datanucleus.store.appengine.DatastorePersistenceHandler.fetchObject(DatastorePersistenceHandler.java:443) at org.datanucleus.state.JDOStateManagerImpl.loadSpecifiedFields(JDOStateManagerImpl.java:1519) at org.datanucleus.state.JDOStateManagerImpl.isLoaded(JDOStateManagerImpl.java:1925) at antshpra.Block.jdoGetModule(Block.java) at antshpra.Block.getModule(Block.java:77) at antshpra.servlets.InitializeDemo.doRequest(InitializeDemo.java:28) at antshpra.Main.doGet(Main.java:76) at javax.servlet.http.HttpServlet.service(HttpServlet.java:693) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093) at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:712) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:237) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139) at org.mortbay.jetty.Server.handle(Server.java:313) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:506) at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:830) at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381) at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:139) at com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:235) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:4950) at com.google.apphosting.base.RuntimePb$EvaluationRuntime$6.handleBlockingRequest(RuntimePb.java:4948) at com.google.net.rpc.impl.BlockingApplicationHandler.handleRequest(BlockingApplicationHandler.java:24) at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:359) at com.google.net.rpc.impl.Server$2.run(Server.java:823) at com.google.tracing.LocalTraceSpanRunnable.run(LocalTraceSpanRunnable.java:56) at com.google.tracing.LocalTraceSpanBuilder.internalContinueSpan(LocalTraceSpanBuilder.java:516) at com.google.net.rpc.impl.Server.startRpc(Server.java:778) at com.google.net.rpc.impl.Server.processRequest(Server.java:351) at com.google.net.rpc.impl.ServerConnection.messageReceived(ServerConnection.java:437) at com.google.net.rpc.impl.RpcConnection.parseMessages(RpcConnection.java:319) at com.google.net.rpc.impl.RpcConnection.dataReceived(RpcConnection.java:290) at com.google.net.async.Connection.handleReadEvent(Connection.java:428) at com.google.net.async.EventDispatcher.processNetworkEvents(EventDispatcher.java:762) at com.google.net.async.EventDispatcher.internalLoop(EventDispatcher.java:207) at com.google.net.async.EventDispatcher.loop(EventDispatcher.java:101) at com.google.net.rpc.RpcService.runUntilServerShutdown(RpcService.java:251) at com.google.apphosting.runtime.JavaRuntime$RpcRunnable.run(JavaRuntime.java:392) at java.lang.Thread.run(Unknown Source) Unexpected exception from servlet: java.lang.NullPointerException --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the 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