并发编程CompletableFuture用法

1.配置线程池

/**
     * int corePoolSize,
     * int maximumPoolSize,
     * long keepAliveTime,
     * TimeUnit unit,
     * BlockingQueue workQueue,
     * ThreadFactory threadFactory,
     * RejectedExecutionHandler handler
     *
     * @return
     */
    @Bean
    public ThreadPoolExecutor threadPoolExecutor(ThreadPoolConfigProperties pool) {
        return new ThreadPoolExecutor(pool.getCoreSize(),
                pool.getMaxSize(),
                pool.getKeepAliveTime(),
                TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(100000),
                Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy()
                );
    }

2.线程池参数配置类

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
/**
	my.thread.core-size=20
	my.thread.max-size=200
	my.thread.keep-alive-time=10
*/
@ConfigurationProperties(prefix = "my.thread")
@Component
@Data
public class ThreadPoolConfigProperties {
	//核心线程数
    private Integer coreSize;
    //最大线程数
    private Integer maxSize;
    //空余线程的存活时间
    private Integer keepAliveTime;
}

3.测试异步任务

	@Autowired
    private ThreadPoolExecutor executor;
	
	//在这里开启一个异步任务，提交给线程池，runAsync()方法没有返回值，需要有返回值的可使用supplyAsync()方法
    @Test
    void testCompletableFuture() {
        CompletableFuture runAsync = CompletableFuture.runAsync(() -> {
            int result = 0;
            for (int i = 0; i <= 100; i++) {
                result += i;
            }
            System.out.println(result);
        }, executor);
    }

4.关于CompletableFuture的其他相关用法
4.1 CompletableFuture的**get()**方法可以获取异步的结果，get方法是一个阻塞式等待的方法，也即get方法会等待异步任务的完成

CompletableFuture completableFuture2 = CompletableFuture.supplyAsync(() -> {
            for (int i = 0; i <= 100; i++) {
                sum2.addAndGet(i);
            }
            return sum2;
     }, executor);
        //获取异步结果
 AtomicInteger integer = completableFuture2.get();

4.2 allOf : 等待所有任务完成完成

AtomicInteger sum = new AtomicInteger();
AtomicInteger sum2 = new AtomicInteger();
CompletableFuture completableFuture1 = CompletableFuture.supplyAsync(() -> {
   for (int i = 0; i <= 100; i++) {
       sum.addAndGet(i);
   }
   return sum;
}, executor);


CompletableFuture completableFuture2 = CompletableFuture.supplyAsync(() -> {
   for (int i = 0; i <= 100; i++) {
       sum2.addAndGet(i);
   }
   return sum2;
}, executor);
AtomicInteger integer = completableFuture2.get();

//allOf : 等待所有任务完成完成，注意get方法，是阻塞式等待，等待上面的异步任务都完成
CompletableFuture.allOf(completableFuture1,completableFuture2).get();

//获取异步结果
 AtomicInteger atomicInteger1 = completableFuture1.get();
 AtomicInteger atomicInteger2 = completableFuture2.get();

 System.out.println("结果是--->"+atomicInteger1.addAndGet(atomicInteger2.intValue()));

4.3 异步任务完成时，whenComplete，exceptionally

CompletableFuture completableFuture3 = CompletableFuture.supplyAsync(() -> {
        for (int i = 0; i <= 10; i++) {
            sum2.addAndGet(i);
        }
        return sum2;
    }, executor).whenComplete((res, exception) -> {
        //当出现异常，可以拿到异常信息，但是无法修改返回数据
        System.out.println("结果是：" + res + ",异常：" + exception);
    }).exceptionally(throwable -> {
        //可以感知异常，同时返回默认值
        return new AtomicInteger(10);
    });

4.4 handle，方法完成后的后续处理

CompletableFuture completableFuture4 = CompletableFuture.supplyAsync(() -> {
      int i = 10 / 2;
       return i;
   }, executor).handle((res, throwable) -> {
       //res 为结果，throwable 为异常
       if (res != null) {
           return res * 2;
       }
       if (throwable != null) {
           return -1;
       }
       return 0;
   });
   System.out.println("completableFuture4--结果是："+completableFuture4.get());

4.5 异步任务串行化

/**
* 异步任务串行化
*      thenAcceptAsync  可以接收上一步获取的结果，但是无返回值
*      thenApplyAsync   可以接收上一步获取的结果，有返回值
*/
   CompletableFuture future = CompletableFuture.supplyAsync(() -> {
       int i = 10 / 2;
       return i;
   }, executor).thenApplyAsync(res -> {
       //res为上一步的结果
       return res * 2;
   }, executor).thenAcceptAsync((res) -> {
       System.out.println("hello ...thenAcceptAsync");
   }, executor);