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List:       tomcat-user
Subject:    Non-blocking IO Question
From:       Daniel Mikusa <dmikusa () gopivotal ! com>
Date:       2013-11-25 0:20:17
Message-ID: FD8FC452-84DC-4D05-BF00-4A5AB65FA457 () gopivotal ! com
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I have a question on usage with non-blocking IO.  I'm setting up a ReadListener which \
implements onDataAvailable like this...

            @Override
            public void onDataAvailable() throws IOException
            {
                while (input.isReady())
                {
                    int read = input.read(buffer);
                    // do something with data...
                }
                // if we're done reading, close up
                if (input.isFinished())
                {
                    complete = true;
                    asyncContext.complete();
                }
            }

This seems to be working, but I'm getting the following NullPointerException.

SEVERE: Exception while processing an asynchronous request
java.lang.NullPointerException
	at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:389)
	at org.apache.coyote.http11.AbstractHttp11Processor.asyncDispatch(AbstractHttp11Processor.java:1618)
  at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:631)
  at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
  at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
  at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1555)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)

After debugging a bit, here is what seems to be happening…

1.) Tomcat calls "onDataAvailable".
2.) The method above runs and reads all of the data.  Because all the data is \
processed, it comples the context. 3.) Tomcat now tries to call "onAllDataRead", but \
I think because I've closed the context it fails.

For reference, here's the section of code from CoyoteAdapter where the NPE is \
generated.

                        Thread.currentThread().setContextClassLoader(newCL);
                        req.getReadListener().onDataAvailable();
                        if (request.isFinished()) {
                            req.getReadListener().onAllDataRead();  // <-- NPE thrown \
here  }

My question here, is my code wrong to call asyncContext.complete() like this?  If I \
restructure it to wait for "onAllDataRead" and complete the context from there then \
everything works OK.

Thanks

Dan
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