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POHow to continuously stream text data to a servlet?
 

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  1. POHow to continuously stream text data to a servlet?
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    <p>I have an Android app which connects to a server and continuously sends some signal data (using HttpURLConnection). On the server a script (shell or python, don't exactly know, it's not my part) currently processes this stream and for every incomming data package sets up a curl request to post this package to a servlet (running in a Jetty 8 web container). This is only a provisionary solution, since I don't know how to directly connect and stream the data to the servlet. As a requirement, the data transfer should use the HTTP protocol in order to be not blocked by any firewall.</p> <p>So, is it possible to initially connect to a servlet and then stream data over a long time, say minutes or hours? I was wondering that I did not find similar questions/solutions. I mean this is not a special scenario. And is this the same operation as uploading a large file to a servlet?</p> <p>The servlet actually looks like this:</p> <pre><code>protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("StreamingServlet#doPost(): IN"); BufferedReader reader = request.getReader(); String data = ""; while ((data = reader.readLine()) != null) { System.out.println("Data: " + data); } reader.close(); System.out.println("StreamingServlet#doPost(): OUT"); } </code></pre> <p>The android app has 3 methods using the HttpURLConnection:</p> <pre><code>private Boolean connect(URL URLdest) { try { connection = (HttpURLConnection) URLdest.openConnection(); connection.setDoOutput(true); connection.setChunkedStreamingMode(0); oSWout = new OutputStreamWriter(connection.getOutputStream()); } catch (IOException e) { return false; } return true; } public void send(String packet) { try { // TODO clOSWout.write and clOSWout.flush block may freeze if connection is lost. Somehow no exception is thrown and thread hangs instead. // It only occurs if the Server breaks the connection oSWout.write(packet); oSWout.flush(); } catch (IOException e) { ... } } public void stopConnection() { try { oSWout.close(); connection.disconnect(); } catch (IOException e) { ... } } </code></pre> <p>What I expect in the end is that when connecting to the servlet, it prints "StreamingServlet#doPost(): IN", then, for each incomming data package it should print the data string and when closing the connection it should print "StreamingServlet#doPost(): OUT" and finally return from the method.</p> <p>But I guess I miss something and this is done in another way in Java EE. I don't know.</p>
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