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kazu2012 / persevere-framework

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NullPointerException in fetchNextPage #262

Open GoogleCodeExporter opened 8 years ago

GoogleCodeExporter commented 8 years ago 
What steps will reproduce the problem?
This problem happens occasionally when our application is using a 
PersevereStore to back a 
scrolling dojo grid.  The grid loads data 25 rows at a time. When this problem 
occurs, we get the 
first 25 rows back fine, but the exception occurs in one of the later requests 
when we scroll the 
grid view.

What is the expected output? What do you see instead?

The expected output is what we usually see: that the later results are returned 
without error.  
Instead, the call to the server fails and we get the following stack trace in 
the log file:

INFO   | jvm 1    | 2010/02/09 07:46:08 | Feb 9, 2010 7:46:08 AM 
org.persvr.remote.PersevereFilter$DefaultHandler call
INFO   | jvm 1    | 2010/02/09 07:46:08 | WARNING: 
java.lang.NullPointerException
INFO   | jvm 1    | 2010/02/09 07:46:08 | Feb 9, 2010 7:46:08 AM 
org.persvr.remote.PersevereFilter$DefaultHandler call
INFO   | jvm 1    | 2010/02/09 07:46:08 | WARNING:
INFO   | jvm 1    | 2010/02/09 07:46:08 | java.lang.NullPointerException
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableArray.fetchNextPage(PersistableArray.java:449)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableArray.get(PersistableArray.java:521)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptableObject.getProperty(ScriptableObject.java:1645)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptRuntime.getObjectIndex(ScriptRuntime.java:1496)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptRuntime.getObjectIndex(ScriptRuntime.java:1481)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c255._c1(FieldValueCore.js:14)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c255.call(FieldValueCore.js)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.callWithChecks(Method.java:140)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:94)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:56)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.optimizer.OptRuntime.call1(OptRuntime.java:66)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c251._c4(authenticate.js:112)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c251.call(authenticate.js)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.ProtectedGlobal$2.callWithChecks(ProtectedGlobal.java:64)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:94)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:56)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.optimizer.OptRuntime.callName(OptRuntime.java:97)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c251._c3(authenticate.js:87)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c251.call(authenticate.js)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.ProtectedGlobal$2.callWithChecks(ProtectedGlobal.java:64)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:94)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.Method.call(Method.java:56)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.security.UserSecurity.getPermissionLevel(UserSecurity.java:36)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableObject.checkSecurity(PersistableObject.java:871)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableObject.get(PersistableObject.java:132)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptableObject.getProperty(ScriptableObject.java:1617)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptRuntime.getObjectProp(ScriptRuntime.java:1437)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptRuntime.getObjectProp(ScriptRuntime.java:1423)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.Interpreter.interpretLoop(Interpreter.java:3027)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.Interpreter.interpret(Interpreter.java:2487)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.InterpretedFunction.call(InterpretedFunction.java:164)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableArray$FilterFunction$1$1.getNext(PersistableArray.jav
a:126)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableArray$FilterFunction$1$1.hasNext(PersistableArray.jav
a:136)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.QueryArray.toArray(QueryArray.java:152)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.PersistableArray$FastSortFunction.call(PersistableArray.java:212
)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.Interpreter.interpretLoop(Interpreter.java:3330)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.Interpreter.interpret(Interpreter.java:2487)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.InterpretedFunction.call(InterpretedFunction.java:164)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.optimizer.OptRuntime.call1(OptRuntime.java:66)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c219._c23(org/persvr/server.js:169)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c219.call(org/persvr/server.js)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.optimizer.OptRuntime.call1(OptRuntime.java:66)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c15._c1(function:2)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c15.call(function)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:398)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3065)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mozilla.javascript.gen.c15.call(function)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.JsonPath.doJsonPath(JsonPath.java:128)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.JsonPath.doJsonPath(JsonPath.java:88)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.data.JsonPath.getTarget(JsonPath.java:79)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.remote.Client$IndividualRequest.requestData(Client.java:245)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.remote.PersevereFilter$DefaultHandler.call(PersevereFilter.java:616)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.persvr.remote.PersevereFilter.doFilter(PersevereFilter.java:357)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.jav
a:1115)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:361)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollecti
on.java:230)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.Server.handle(Server.java:324)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:534)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.ja
va:864)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:533)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:207)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
INFO   | jvm 1    | 2010/02/09 07:46:08 |       at 
org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)

What version of the product are you using? On what operating system?
Persevere 1.0

Other information:
Our codebase has custom authentication and access control code, which may be 
evident in the 
stack trace shown.  However, examination of the relevant code in Persevere 
leads us to believe 
that the problem is in the Persevere code, not in our access control.  
fetchNextPage() is a 
synchronized method which uses an iterator and then sets it to null.  We can't 
find the code that 
initializes the iterator (at least not inside the synchronized region where it 
can be guaranteed to 
execute before the iterator is needed).  It seems to us that multiple requests 
for multiple pages 
made to a server under load could cause the synchronized block to execute twice 
without any 
other code executing in between, which could lead to this problem.  As with 
most 
synchronization issues, this doesn't happen every time, so it is difficult to 
reproduce.

Original issue reported on code.google.com by dsta...@gmail.com on 9 Feb 2010 at 7:12

GoogleCodeExporter commented 8 years ago 
I think this was fixed by commit 701

Original comment by dsta...@gmail.com on 23 Mar 2010 at 11:08