Created attachment 32157 [details]
related java code files

stack trace:
28-Oct-2014 11:56:26.891 SEVERE [http-nio-8080-exec-5] org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun 
 java.lang.NullPointerException
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1538)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:744)

related code:
TextReadListener
	public synchronized void onAllDataRead() throws IOException {
		logger.debug("onAllDataRead", new Exception("onAllDataRead"));
		final String text = (buf != null ? buf.toString("UTF-8") : "");
		logger.debug("onAllDataRead> text={}", text);
		HttpServletRequest req = (HttpServletRequest) asyncCtx.getRequest();
		logger.debug("onAllDataRead> uri={}, User-Agent={}, params={}", req.getRequestURI(),
				req.getHeader("User-Agent"), req.getParameterMap());
		final ServletOutputStream out = asyncCtx.getResponse().getOutputStream();
		asyncCtx.start(new Runnable() {
			@Override
			public void run() {
				try {
					logger.debug("start sleep");
					TimeUnit.SECONDS.sleep(1);
					logger.debug("sleep finished, start writing");
					WriteListener writeListener = new TextWriteListener(("test" + text).getBytes("UTF-8"), asyncCtx,
							out);
					out.setWriteListener(writeListener);
				} catch (Throwable e) {
					logger.error("impossible ex", e);
				}
			}
		});
	}

If I just invoke out.setWriteListener in onAllDataRead method (not in asyncCtx.start), then that's ok.

Detailed java code is in attachment