Java异步执行之CompletableFuture异步执行并获取结果使用

CompletableFuture介绍

CompletableFuture 是Java 8中引入的一个强大的异步编程工具，它实现了 Future 接口和 CompletionStage 接口。与传统的 Future 相比，CompletableFuture 提供了更多的控制能力，如手动完成、异常处理和多个Future的组合等。

1.方法介绍

runAsync

创建没有返回值的异步任务

//默认线程池, 不一定会使用ForkJoinPool, 根据任务并行度来计算
   public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier) {
        return asyncSupplyStage(ASYNC_POOL, supplier);
    }
//可以自定以线程池
    public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier,
                                                       Executor executor) {
        return asyncSupplyStage(screenExecutor(executor), supplier);
    }

示例

public static <T,R> List<R> batchQuery(BatchQueryFunction<T,R> batchQueryFunction, List<T> t) throws Exception {
      ThreadPoolUtils poolUtils = ThreadPoolUtils.get();//自定义线程池
      AtomicReference<List<R>> listAtomicReference = new AtomicReference<>(Lists.newArrayList());//线程安全问题
      CompletableFuture.allOf(t.stream().map(id -> CompletableFuture.runAsync(() -> {
          R r = batchQueryFunction.accept(id);
          List<R> jsonObjects = listAtomicReference.get();
          jsonObjects.add(r);
          listAtomicReference.set(jsonObjects);
      },poolUtils).exceptionally(ex -> {//异常处理
          log.error("Async operation failed",ex);
          throw new RuntimeException(ex);
      })).toArray(CompletableFuture[]::new)).join();// join阻塞获取所有结果
      log.info("list size: {}", listAtomicReference.get().size());
      shutdownThreadPool(poolUtils);//关闭线程池
      return listAtomicReference.get();
}

supplyAsync

supplyAsync是创建带有返回值的异步任务, 也是有两个方法

   public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier) {
        return asyncSupplyStage(ASYNC_POOL, supplier);
    }
    public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier,
                                                       Executor executor) {
        return asyncSupplyStage(screenExecutor(executor), supplier);
    }

示例

       CompletableFuture<Integer> integerCompletableFuture = CompletableFuture.supplyAsync(() -> {
            try {
                Thread.sleep(1000);
                return 1;
            }catch(InterruptedException e) {
                e.printStackTrace();
            }
            return 0;
        });
        Integer i = integerCompletableFuture.get();
        System.out.println("i = " + i);
    }

2.异步回调

处理计算结果thenApply ,要回调的结果

       CompletableFuture<String> completableFuture
                = CompletableFuture.supplyAsync(() -> "等一会!");

        CompletableFuture<String> future = completableFuture
                .thenApply(s -> s + "等到你了");
        System.out.println("future = " + future.get()); //future = 等一会!等到你了

不要回调的结果使用thenAccept

        CompletableFuture<String> completableFuture
                = CompletableFuture.supplyAsync(() -> "等一会!");
        CompletableFuture<Void> future1 = completableFuture
                .thenAccept(s1-> System.out.println("future1 = " + s1));
        future1.get();
    }

thenRun

可以做一些后置操作

组合操作

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