JavaEE：構建並刷新線程中的響應

我正在嘗試編寫一個線程化的Java EE servlet。
每個線程將執行一些處理，並將其結果寫入單個HTTP塊（使用HTTP傳輸編碼：分塊）。
每個塊將在可用時立即發送到客戶端。
我有問題編寫和刷新每個線程內的輸出。
爲了舉例，下面的代碼生成了5個線程，它們生成一個隨機字符串，將它寫入輸出緩衝區並通過同步函數調用刷新該緩衝區。JavaEE：構建並刷新線程中的響應

public class TestServer extends HttpServlet { 
    private PrintWriter m_out; 

    public TestServer() { 
     super(); 
    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     m_out = response.getWriter(); 

     m_out.print("gonna start\n"); 
     m_out.flush(); 

     ThreadPoolExecutor thread_pool = (ThreadPoolExecutor) Executors.newFixedThreadPool(10); 
     for(int i = 0; i < 5; i++) { 
     thread_pool.execute(new Runnable() { 
     private ReentrantLock m_lock = new ReentrantLock(); 
     @Override 
     public void run() { 
       SecureRandom random = new SecureRandom(); 
       m_lock.lock(); 
       try { 
        display(new BigInteger(1300, random).toString(32)+"\n"); 
       } 
       finally { 
        m_lock.unlock(); 
       } 
      } 
     }); 
     } 
     thread_pool.shutdown(); 
     try { 
     thread_pool.awaitTermination(120, TimeUnit.SECONDS); 
     } 
     catch (InterruptedException e1) { 
     log("thread interrupted"); 
     e1.printStackTrace(); 
     } 
     m_out.print("ok we done\n"); 
     m_out.close(); 
    } 

    void display(String content) { 
     m_out.print(content); 
     m_out.flush(); 
    } 
}

在一段時間後，該代碼將產生以下輸出：

Server: Apache-Coyote/1.1 
Transfer-Encoding: chunked 
Date: Mon, 14 Mar 2011 22:26:15 GMT 
Connection: close 

gonna start 
fmclslvi1p8pmpbnfg8ikfpp3uce5db0ncoms3d4i3tjnbfmrab9nr2cue0to8hra8s87f7r1v2ff2n3c5s68cbqnib3cmn21ddn45k829po4qkgaqkgsdr35uuqqhskvfdj4psldgp58r63g85kbjnn0i53d3sg5kibbe4tsigcavbp2oeee5s63ro68k2eu74t237jghsmtsaocpo771jjtqdh071ogtfp7bel1d6mlj63f88o2adg88uc07l8f62r 
fmclslvi1p8pmpbnfg8ikfpp3uce5db0ncoms3d4i3tjnbfmrab9nr2cue0to8hra8s87f7r1v2ff2n3c5s68cbqnib3cmn21ddn45k829po4qkgaqkgsdr35uuqqhskvfdj4psldgp58r63g85kbjnn0i53d3sg5kibbe4tsigcavbp2oeee5s63ro68k2eu74t237jghsmtsaocpo771jjtqdh071ogtfp7bel1d6mlj63f88o2adg88uc07l8f62r 
5jf605re18gpuqpvr30gfku1l905edlq7rqrslrh0mkubvlj91crk18htfnbeni3r7c36eukffl04sppprqdco6k23dm0mev9noa5f75frjls40tigeduo2jmfe3f8bneja11nn09giplo0kpn45tnm4etp9jhp5h42gim1ia9lm8s5c6m39gm7h0mcgpj0fogmo2bo319tlgppuhcp6t887s5jvm52fg191mc55cgb7inlir8ail3gbnsdea46vj041 
jggsrderm9rpegoq9gapjl4dk14ubc4mb0nfq2bdkqtrdvuihv8q8f0dbqm63n7ojghcchb4c7gbp77011fl8hrfrl0mf9c3mfvhk1acfuofedjido44247ffs8lt28304o8i1luumbnbvbdrqdl8nno4b3t0pul8ep0t6vsgl7bp64pnlfiisepvq1urujtsbbou6batft6ide1qu8ps783qhn07v8n3i2jdj20v599np1ahrkcso9is0g1ja1e31fl 
4h1rkt6n478h83db250ldqt517dn40ae5960qmsr5nnsqlv5av2eqmn61sruug2etqjn7h4l5lh2i9i0q1s08d5f6kpmaep8oms77u91gvfop1j2vds6v6o85fbn3cmi27it9l7ogrm305eunsrdgnblhn2bvisa2vkhhi469mj22oklgc3sqcd59eh6e52uhop60vjdq20qcq9up825v446eukk19jmoi2sisnka03kagb7ueaqmdq6rd9lq0g25l20 
n1hv30da7d7naqs34r0hgf5r7r75gr8u98vko7krfdogka2d0t0pb7koiuojdm0rn3uc99g9a8epf81e1rkgn98fho2vih003vt759d8asoou9qmnmu5gluejlarbalcf4dk2kic9l9fhhv45vghcuu8tfppo2dapvrnafoetuqlgt4eb6o997iod3fcd5jpfqa47mhnfd5p81fudfcvqej6t69q7hv38nqbgdgtjj73thn534g1j3pc4as8c4dkj8dj 
ok we done

你看到1條第一動態生成線被重複。
這似乎表明PrintWriter.flush（）方法不能同步。

爲什麼這不起作用，我能做些什麼來實現我的目標？

謝謝。

來源

2011-03-14 Pierre

以供將來參考，我想我得到了它與下面的代碼工作：

@SuppressWarnings("serial") 
public class TestServer extends HttpServlet { 
    private final int THREADPOOL_SIZE = 10; 
    private ThreadPoolExecutor thread_pool; 

    public void init(ServletConfig config) throws ServletException { 
     super.init(config); 
     thread_pool = (ThreadPoolExecutor) Executors.newFixedThreadPool(THREADPOOL_SIZE); 
    } 

    public void destroy() { 
     thread_pool.shutdownNow(); 
    } 

    public TestServer() { 
      super(); 
    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     CompletionService<String> completion_service_pool = new ExecutorCompletionService<String>(thread_pool); 
     int task_num = 10; 
     final int line_length = 13000; 
     for(int i = 0; i < task_num; i++) { 
     completion_service_pool.submit(new Callable<String>(){ 
      @Override 
      public String call() { 
       Random rn = new Random(); 
       int sleep_seconds = Math.abs(rn.nextInt() % 10); 
       try { 
        Thread.sleep(sleep_seconds * 1000); 
       } 
       catch (Exception e) { 

       } 
       return String.format("Slept for %d seconds. %s<br>\n", sleep_seconds, new BigInteger(line_length, rn).toString(32)); 
      } 
     }); 
     } 

     PrintWriter out = response.getWriter(); 
     response.setContentType("text/html"); 
     out.print("gonna start<br>\n"); 
     out.flush(); 

     for(int i = 0; i < task_num;) { 
     try { 
      Future<String> result_task = completion_service_pool.poll(); 
      if(result_task != null) { 
       String result_string = result_task.get(); 
       out.print(result_string); 
       out.flush(); 
       i++; 
      } 
     } 
     catch (Exception e) { 
     } 
     } 

     out.print("ok we done<br>\n"); 
     out.close(); 
    } 
}

來源

2011-03-15 20:05:01 Pierre

JavaEE：構建並刷新線程中的響應

回答

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