异步回调(Future)

异步回调（Future） #

我们平时一般都是使用它的实现类：CompletableFuture

没有返回值的runAsync异步回调 #

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class FutureTest {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        // 发起 一个 请求

        System.out.println(System.currentTimeMillis());
        System.out.println("---------------------");
        CompletableFuture<Void> future = CompletableFuture.runAsync(()->{
            //发起一个异步任务
            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+".....");
        });
        System.out.println(System.currentTimeMillis());
        System.out.println("------------------------------");
        //输出执行结果
        System.out.println(future.get());  //获取执行结果
    }
}

有返回值的异步回调supplyAsync #

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class FutureTest {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //有返回值的异步回调
        CompletableFuture<Integer> completableFuture=CompletableFuture.supplyAsync(()->{
            System.out.println(Thread.currentThread().getName());
            try {
                TimeUnit.SECONDS.sleep(2);
                int i=1/0;
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return 1024;
        });
        System.out.println(completableFuture.whenComplete((t, u) -> {
            //success 回调
            System.out.println("t=>" + t); //正常的返回结果
            System.out.println("u=>" + u); //抛出异常的 错误信息
        }).exceptionally((e) -> {
            //error回调
            System.out.println(e.getMessage());
            return 404;
        }).get());
    }
}