CompletableFuture handle和whenComplete区别

桃扇骨 2023-02-20 07:22 5阅读 0赞

## handle 方法和whenComplete方法类似， ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70]  
如果是方法后面加了Async表示异步执行,就是从ForkJoinPool.commonPool-worker线程池里里面重新选择线程,可能是同一个线程,可能不是同一个线程,如果没有加,就代表使用返回当前结果的线程执行…

## 1. 接收参数不同 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 1]  
whenComplete接收的是BiConsumer,handler接收的是BiFunction;  
顾名思义,BiConsumer是直接消费的,而BiFunction是有返回值的,

BiConsumer没有返回值,而BiFunction是有的;  
[BiConsumer,BiFunction区别][BiConsumer_BiFunction]

## 2. 返回参数不同 ##

一个是返回传进去的值,一个是返回处理返回的值  
handler接收的是一个 BiFunction<? super T,Throwable,? extends U> fn 类型的参数，因此有 whenComplete 方法和 转换的功能 (thenApply)  
写一个简单的测试:

@Test
      public void test3() throws Exception { 
        CountDownLatch countDownLatch = new CountDownLatch(1);
    
        CompletableFuture<Integer> future1 = CompletableFuture.supplyAsync(() -> { 
          System.out.println(Thread.currentThread().getName() + "进行一连串操作1....");
          try { 
            TimeUnit.SECONDS.sleep(3);
          } catch (InterruptedException e) { 
            e.printStackTrace();
          }
          return 1;
        });
    
        //whenComplete方法,返回的future的结果还是1
        CompletableFuture<Integer> future = future1.whenComplete((x, y) -> { 
          try { 
            TimeUnit.SECONDS.sleep(3);
          } catch (InterruptedException e) { 
            e.printStackTrace();
          }
          System.out.println(Thread.currentThread().getName() + "whenComplete,future返回:" + x);
        });
    
        //handler返回的future结果是字符串"2"
        CompletableFuture<String> handle = future.handle((x, y) -> { 
          System.out.println(Thread.currentThread().getName() + "handle接收的结果:" + x);
          countDownLatch.countDown();
          return "2";
        });
        CompletableFuture<Integer> handle1 = handle.handle((x, y) -> { 
          System.out.println(Thread.currentThread().getName() + "handle返回的结果:" + x);
          countDownLatch.countDown();
          return 2;
        });
        countDownLatch.await();
        System.out.println(1);
    
      }

执行的结果:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 2]  
***说到底,handle 方法和whenComplete方法的区别主要是Consumer,BiConsumer和Function,BiFunction的区别***

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200630103050436.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/2020062919115162.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70
[BiConsumer_BiFunction]: https://yidajava.blog.csdn.net/article/details/107026732
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200630102745407.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70