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Calling flushBuffer() in TOMCAT 6.0.20 returning NullPointerException.

Posts: 4
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I have a servlet and when i call reponse.getWriter().flushBuffer() OR reponse.getWriter().println("SOME TEXT"), sometimes it gives following types of errors. This error does not occur always but sometimes. What can be the reason for this?

*********** ERROR ************
at org.apache.tomcat.util.http.MimeHeaders.setValue(MimeHeaders.java:267)
at org.apache.coyote.http11.Http11Processor.prepareResponse(Http11Processor.java:1578)
at org.apache.coyote.http11.Http11Processor.action(Http11Processor.java:944)
at org.apache.coyote.Response.action(Response.java:183)
at org.apache.coyote.Response.sendHeaders(Response.java:379)
at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:305)
at org.apache.catalina.connector.OutputBuffer.close(OutputBuffer.java:273)
at org.apache.catalina.connector.CoyoteWriter.close(CoyoteWriter.java:108)
at com.onmobile.platform.sovxml.ControlServlet.doGet(ControlServlet.java:3482)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:567)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:361)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at java.lang.Thread.run(Thread.java:595

Author and all-around good cowpoke
Posts: 13078
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Unfortunately I only have the Tomcat 6.0.18 source code right here and line 1578 does not make sense for this NPE. The prepareResponse method is quite long and it looks like it depends on lots of variables being set when the MimeHeaders method is called.

I suggest you download the full source and take a look at that line. Let us know what you find.

chinmay totekar
Posts: 4
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Got the problem..
The problem was response.getWriter() object was declared as global in servlet, so it became common to all threads. and if one thread closes it, it used to give NullPtrException in other threads.

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