如何等待我的線程工廠完成其所有任務？

Question

我正在使用Spring 4.3.8.RELEASE和Java 7.我想創建一個線程工廠來幫助管理我的應用程序中的某些工作人員。我宣佈我的線程工廠是這樣的

<bean id="myprojectThreadFactory" class="org.springframework.scheduling.concurrent.CustomizableThreadFactory"> 
    <constructor-arg value="prefix-"/> 
</bean> 
<bean id="myprojectTaskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"> 
    <property name="threadFactory" ref="myprojectThreadFactory"/> 
    <property name="corePoolSize" value="${myproject.core.thread.pool.size}" /> 
    <property name="maxPoolSize" value="${myproject.max.thread.pool.size}" /> 
</bean> 

但是，我在加入線程時遇到了問題。也就是說，我要等到所有的工作具有一定的任務，所以我有

m_importEventsWorker.work(); 
    m_threadExecutor.shutdown(); 
    System.out.println("done."); 

在我的線程池，像這樣

public void work(final MyWorkUnit pmyprojectOrg) 
{ 
    final List<MyWorkUnit> allOrgs = new ArrayList<MyWorkUnit>(); 
    if (pmyprojectOrg != null) 
    { 
     processData(pmyprojectOrg.getmyprojectOrgId()); 
    } else { 
     allOrgs.addAll(m_myprojectSvc.findAllWithNonEmptyTokens()); 
     // Cue up threads to execute 
     for (final MyWorkUnit myprojectOrg : allOrgs) 
     { 
      m_threadExecutor.execute(new Thread(new Runnable(){ 
       @Override 
       public void run() 
       { 
        System.out.println("started."); 
        processData(myprojectOrg.getmyprojectOrgId()); 
       } 
      })); 
     } // for 

然而，什麼會打印出執行繼續之前完成是

done. 
started. 
started. 

很清楚，我不是在等待。什麼是正確的方式來等待我的線程完成工作？

Answer 1

由於我使用Spring的ThreadPoolTask​​Executor類，我發現低於適合我的需求......

protected void waitForThreadPool(final ThreadPoolTaskExecutor threadPoolExecutor) 
{ 
    threadPoolExecutor.setWaitForTasksToCompleteOnShutdown(true); 
    threadPoolExecutor.shutdown();  
    try { 
     threadPoolExecutor.getThreadPoolExecutor().awaitTermination(30, TimeUnit.SECONDS); 
    } catch (IllegalStateException e) { 
     e.printStackTrace(); 
    } catch (InterruptedException e) { 
     e.printStackTrace(); 
    } 
} // waitForThreadPool 

Answer 2

A CountDownLatch用給定的計數初始化。該計數通過調用countDown()方法遞減。等待此計數達到零的線程可以調用await()方法之一。調用await()會阻塞該線程，直到計數達到零。

您可以使用CountDownLatch主線程等待完成所有的task.You可以宣佈CountDownLatch與大小在主線程中調用await()方法任務CountDownLatch latch = new CountDownLatch(3);的數量等，每個任務完成呼叫countDown()

public void work(final MyWorkUnit pmyprojectOrg) 
{ 
    final List<MyWorkUnit> allOrgs = new ArrayList<MyWorkUnit>(); 
    if (pmyprojectOrg != null) 
    { 
     processData(pmyprojectOrg.getmyprojectOrgId()); 
    } else { 
     allOrgs.addAll(m_myprojectSvc.findAllWithNonEmptyTokens()); 

     CountDownLatch latch = new CountDownLatch(allOrgs.size()); 

     // Cue up threads to execute 
     for (final MyWorkUnit myprojectOrg : allOrgs) 
     { 
      m_threadExecutor.execute(new Thread(new Runnable(){ 
       @Override 
       public void run() 
       { 
        System.out.println("started."); 
        processData(myprojectOrg.getmyprojectOrgId()); 
        latch.countDown(); 
       } 
      })); 
     } 
     //After for loop 
     latch.await();  

實施例：

CountDownLatch latch = new CountDownLatch(3); 

Waiter  waiter  = new Waiter(latch); 
Decrementer decrementer = new Decrementer(latch); 

new Thread(waiter)  .start(); 
new Thread(decrementer).start(); 

public class Waiter implements Runnable{ 

    CountDownLatch latch = null; 

    public Waiter(CountDownLatch latch) { 
     this.latch = latch; 
    } 

    public void run() { 
     try { 
      latch.await(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 

     System.out.println("Waiter Released"); 
    } 
} 

公共類遞減器實現Runnable {

CountDownLatch latch = null; 

public Decrementer(CountDownLatch latch) { 
    this.latch = latch; 
} 



public void run() { 

     try { 
      Thread.sleep(1000); 
      this.latch.countDown(); 

      Thread.sleep(1000); 
      this.latch.countDown(); 

      Thread.sleep(1000); 
      this.latch.countDown(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 
    } 
} 

Answer 3

可以使用的ExecutorService創建一個固定的線程池，並檢查池大小是否爲空沒有：

ExecutorService executor = Executors.newFixedThreadPool(50); 

如果使用此執行運行任務，並通過使用@Scheduled固定利率或FIXEDDELAY定期檢查線程池的大小，你可以看到，如果他們完成與否。

ThreadPoolExecutor poolInfo = (ThreadPoolExecutor) executor; 
Integer activeTaskCount = poolInfo.getActiveCount(); 

if(activeTaskCount = 0) { 
    //If it is 0, it means threads are waiting for tasks, they have no assigned tasks. 
    //Do whatever you want here! 
}