### java future

Runnable的任务是没有返回值，也不能抛出异常的
java.util.concurrent.Callable接口，可以返回一个对象或者抛出异常

使用jdk的这种方式提交Callble任务，如果使用Future等待返回结果，这里就是阻塞的。所以，可能某一个任务时间很长会拖累整个主任务的执行。

 1 public class TestFuture {
 2     final static ExecutorService executorService = Executors.newCachedThreadPool();
 3 
 4     public static void main(String[] args) {
 5         Future<Boolean> booleanTask = executorService.submit(new Callable<Boolean>() {
 6             @Override
 7             public Boolean call() throws Exception {
 8 
 9                 return true;
10             }
11         });
12 
13         while (true) {
14             if (booleanTask.isDone() && !booleanTask.isCancelled()) {
15                 try {
16                     TimeUnit.SECONDS.sleep(5);
17                     Boolean result = booleanTask.get();
18                     System.out.println("BooleanTask : " + result);
19                 } catch (Exception e) {
20                     e.printStackTrace();
21                 }
22                 break;
23             }
24         }
25 
26         if (booleanTask.isDone() && !booleanTask.isCancelled()) {
27             try {
28 
29                 Boolean result = booleanTask.get();
30                 System.out.println("BooleanTask : " + result);
31             } catch (Exception e) {
32                 e.printStackTrace();
33             }
34         }
35         System.out.println(booleanTask.isCancelled());
36         System.out.println("BooleanTask is over");
37 
38         Future<String> stringTask = executorService.submit(new Callable<String>() {
39             @Override
40             public String call() throws Exception {
41 
42                 return "Hello world";
43             }
44         });
45 
46         /**
47         cancel只能取消还没有提交或者执行的线程任务，所以这里无法确定是否成功取消了submit的callab le任务，stringTask.isCancelled()的值也就是不确定的
48         **/
49 
50         stringTask.cancel(true);
51 
52         while (true) {
53             if (stringTask.isDone() && !stringTask.isCancelled()) {
54                 try {
55 
56                     TimeUnit.SECONDS.sleep(5);
57                     String result = stringTask.get();
58                     System.out.println("StringTask : " + result);
59                 } catch (Exception e) {
60                     e.printStackTrace();
61                 }
62 
63                 break;
64             }
65 
66         }
67 
68 
69         System.out.println("StringTask is over");
70         System.out.println(stringTask.isDone());
71         System.out.println(stringTask.isCancelled());
72 
73     }
74 } 

###代码片段

 1 List<Future<Integer>> futures = Lists.newArrayList();
 2         for (final AuditTask task : taskList) {
 3             futures.add(ThreadUtils.CUSTOM_THREAD_EXECUTOR.submit(new Callable<Integer>() {
 4 
 5                 @Override
 6                 public Integer call() throws Exception {
 7                     try {
 8                         sendToAkaOperation(task);
 9                         return COUNT_ONE;
10                     } catch (Exception e) {
11                         return COUNT_ZERO;
12                     }
13                 }
14             }));
15         }
16 
17         int count = 0;
18         for (Future<Integer> future : futures) {
19             try {
20             //阻塞，可能由于某个任务的执行影响整个主任务
21                 count = count + future.get();
22             } catch (Exception e) {
23                 log.error("一次推送auditPageDataWide到AKA任务异常：" + e.getMessage());
24             }
25         }
26         log.info("一次送审任务结束，本次送审任务完成送审AKA物料数目： " + count);
27     }

### guava future

ListenableFuture是可以监听的Future,如果任务完成或者失败可以自动回调函数。这样多个任务可以异步执行，并且可以实现无阻塞的获取每个任务的执行结果。

 1 public class TestListenableFuture {
 2     final static ListeningExecutorService LISTENING_EXECUTOR_SERVICE = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool());
 3 
 4     public static void main(String[] args) {
 5         ListenableFuture<Boolean> booleanTask = LISTENING_EXECUTOR_SERVICE.submit(new Callable<Boolean>() {
 6             @Override
 7             public Boolean call() throws Exception {
 8                 TimeUnit.SECONDS.sleep(5);
 9                 return true;
10             }
11         });
12 
13         Futures.addCallback(booleanTask, new FutureCallback<Boolean>() {
14             @Override
15             public void onSuccess( Boolean aBoolean) {
16                 System.out.println("BooleanTask : " + aBoolean);
17             }
18 
19             @Override
20             public void onFailure(Throwable throwable) {
21 
22             }
23         });
24 
25         ListenableFuture<String> stringTask = LISTENING_EXECUTOR_SERVICE.submit(new Callable<String>() {
26             @Override
27             public String call() throws Exception {
28                 return "Hello world";
29             }
30         });
31 
32         Futures.addCallback(stringTask, new FutureCallback<String>() {
33             @Override
34             public void onSuccess(String aBoolean) {
35                 System.out.println(Thread.currentThread().getName());
36                 System.out.println("StringTask : " + aBoolean);
37             }
38 
39             @Override
40             public void onFailure(Throwable throwable) {
41 
42             }
43         });
44 
45     }
46 }

输出结果：
main
StringTask : Hello world
BooleanTask : true