content: package com.taobao.yugong.common.utils.thread;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutorCompletionService;
  import java.util.concurrent.Future;
  import java.util.concurrent.ThreadPoolExecutor;
  
  /**
   * 多线程执行器模板代码，otter中好多地方都写多线程，比较多的都是重复的逻辑代码，抽象一下做个模板把
   *
   * <pre>
   * 示例代码：
   * ExecutorTemplate template = new ExecutorTemplate(executor);
   * ...
   * try {
   *    for ( ....) {
   *       template.submit(new Runnable() {})
   *    }
   * 
   *    List<?> result = template.waitForResult();
   *    // do result
   * } finally {
   *    template.clear();
   * }
   * 
   * 注意：该模板工程，不支持多业务并发调用，会出现数据混乱
   * </pre>
   *
   * @author agapple 2013-2-26 下午10:46:43
   */
  public class ExecutorTemplate {
  
      private volatile ExecutorCompletionService comletions = null;
      private volatile List<Future>              futures    = null;
  
      public ExecutorTemplate(ThreadPoolExecutor executor){
          futures = Collections.synchronizedList(new ArrayList<Future>());
          comletions = new ExecutorCompletionService(executor);
      }
  
      public void submit(Runnable task) {
          Future future = comletions.submit(task, null);
          futures.add(future);
          check(future);
      }
  
      public void submit(Callable<Exception> task) {
          Future future = comletions.submit(task);
          futures.add(future);
          check(future);
      }
  
      private void check(Future future) {
          if (future.isDone()) {
              // 立即判断一次，因为使用了CallerRun可能当场跑出结果，针对有异常时快速响应，而不是等跑完所有的才抛异常
              try {
                  future.get();
              } catch (Throwable e) {
                  // 取消完之后立马退出
                  cacelAllFutures();
                  throw new RuntimeException(e);
              }
          }
      }
  
      public synchronized List<?> waitForResult() {
          List result = new ArrayList();
          RuntimeException exception = null;
          // 开始处理结果
          int index = 0;
          while (index < futures.size()) { // 循环处理发出去的所有任务
              try {
                  Future future = comletions.take();// 它也可能被打断
                  result.add(future.get());
              } catch (Throwable e) {
                  exception = new RuntimeException(e);
                  // 如何一个future出现了异常，就退出
                  break;
              }
  
              index++;
          }
  
          if (exception != null) {
              // 小于代表有错误，需要对未完成的记录进行cancel操作，对已完成的结果进行收集，做重复录入过滤记录
              cacelAllFutures();
              throw exception;
          } else {
              return result;
          }
      }
  
      public void cacelAllFutures() {
          for (Future future : futures) {
              if (!future.isDone() && !future.isCancelled()) {
                  future.cancel(true);
              }
          }
      }
  
      public void clear() {
          futures.clear();
      }
  
  }
  