NullPointerException at line 1472 of CoyoteRequest.java (setAttribute)

[We...@ubs.com]

Hello,

I am receiving an intermittent NullPointerException when I call the request.setAttribute(java.lang.String name, java.lang.Object o) method from my servlet.  The error is not consistently reproducible and only happens infrequently.  We are running tomcat 5.0.25 on a Linux server.  The error is occurring on a page that has about 100 users accessing it, auto-refreshing every 30-60 seconds.  The object I am setting as an attribute is of type List (ArrayList) and it is not null when I set it.

A printStackTrace shows that the error is occurring at line 1472 of CoyoteRequest.java on context.getapplicationEventListenders: 
	Object listeners[] = context.getApplicationEventListeners();

I assume that, when the exception is thrown, context is null, but I'm not sure what would cause this.  In every instance this error does not occur again when the user refreshes his/her request.

Is this a known bug in Tomcat 5.0.25?  Otherwise, could it be some sort of memory problem?  What would cause context to infrequently and seemingly randomly be null?
 
A full stack trace is below.  The name of my servlet is OrderBook.  I greatly appreciate any help.

2005-01-18 09:14:51 StandardWrapperValve[OrderBook]: Servlet.service() for servlet OrderBook threw exception
java.lang.NullPointerException
	at org.apache.coyote.tomcat5.CoyoteRequest.setAttribute(CoyoteRequest.java:1472)
	at org.apache.coyote.tomcat5.CoyoteRequestFacade.setAttribute(CoyoteRequestFacade.java:349)
	at com.ubs.koba.web.OrderBookController.doProcess(OrderBookController.java:36)
	at com.ubs.koba.web.BaseServlet.init(BaseServlet.java:92)
	at com.ubs.koba.web.BaseServlet.doGet(BaseServlet.java:139)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
	at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
	at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:793)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:702)
	at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:571)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:644)
	at java.lang.Thread.run(Thread.java:534)




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