Spring boot使用@Async实现异步调用

大多数情况下都是通过同步的方式来实现交互处理的

但是在处理与第三方系统交互的时候，经常会响应迟缓

可以使用@Async实现异步调用

1.使用@Async

使用步骤：

使用@EnableAsync开启异步；

定义Spring组件，使用@Component和@Async

（1）添加依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

 （2）修改启动类

添加@EnableAsync开启异步

package com.abc.xyz;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;

@SpringBootApplication
@EnableAsync
public class XyzApplication {

    public static void main(String[] args) {
        SpringApplication.run(XyzApplication.class, args);
    }

}

（3）定义Spring 组件

package com.abc.xyz;

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Component;

import java.util.concurrent.Future;

@Component
public class MyTask {

    @Async
    public void task1() {
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task1任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task1任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
    }

    @Async
    public Future<String> task2() {
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task2任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task2任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        return new AsyncResult<>("success");
    }
}

（4）测试

package com.abc.xyz.controller;

import com.abc.xyz.MyTask;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @Autowired
    private MyTask myTask;
    @RequestMapping("/test")
    public String test(){
        System.out.println("task before");
        myTask.task1();
        System.out.println("task after");
        return "OK";
    }
}

启动项目

浏览器打开http://localhost:8080/test

输出OK

控制台输出

task before
task after
task1任务开始, timestamp=1576415623066, threadId=51, threadName=task-1
task1任务结束, timestamp=1576415626067, threadId=51, threadName=task-1

从输出看出，任务是异步执行的

2.带有返回值的异步

返回值Future<T>

添加带返回值的task2()

package com.abc.xyz;

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Component;

import java.util.concurrent.Future;

@Component
public class MyTask {

    @Async
    public void task1() {
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task1任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task1任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
    }

    @Async
    public Future<String> task2() {
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task2任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task2任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        return new AsyncResult<>("success");
    }
}

测试方法

package com.abc.xyz.controller;

import com.abc.xyz.MyTask;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.Future;

@RestController
public class HelloController {

    @Autowired
    private MyTask myTask;
    @RequestMapping("/test")
    public String test(){
        try {
            long start = System.currentTimeMillis();
            System.out.println("task before");
            Future<String> rs = myTask.task2();
            System.out.println(rs.get());
            myTask.task1();
            System.out.println("task after");
            System.out.println("执行时间"+(System.currentTimeMillis()-start));
        }catch (Exception e){
            e.printStackTrace();
        }
        return "OK";
    }
}

启动项目，控制台输出

task before
task2任务开始, timestamp=1576416889468, threadId=51, threadName=task-1
task2任务结束, timestamp=1576416892469, threadId=51, threadName=task-1
success
task after
执行时间3016
task1任务开始, timestamp=1576416892474, threadId=52, threadName=task-2
task1任务结束, timestamp=1576416895474, threadId=52, threadName=task-2

说明：

　　@Async注解声明的方法，返回类型要么为void，要么为Future

　　方法是异步调用的，无法立即返回结果，如果声明为其它返回类型，获取到的是null

　　声明为Future，则可以获取到任务的执行结果，结果用Future的get()方法获取

3.异常处理

（1）带返回值的异常处理

　　带Future类型的返回值时，在调Future的get()方法获取任务的执行结果时抛出的异常

修改task2

@Async
    public Future<String> task2() throws Exception{
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task2任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task2任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        return new AsyncResult<>("success");
    }

（2）不带返回值的异常处理

　　不带返回值的异常无法被调用者捕获，可以实现AsyncUncaughtExceptionHandler来处理

添加 MyAsyncUncaughtExceptionHandler 实现 AsyncUncaughtExceptionHandler

package com.tydt.bim.common;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;

import java.lang.reflect.Method;

public class MyAsyncUncaughtExceptionHandler implements AsyncUncaughtExceptionHandler {

    private final Logger logger = LoggerFactory.getLogger(MyAsyncUncaughtExceptionHandler.class);
    @Override
    public void handleUncaughtException(Throwable ex, Method method, Object... params) {
        logger.error("Exception occurs in async method:",ex.getMessage());
    }
}

　　添加 AsyncConfig 实现 AsyncConfigurer 并覆盖 AsyncUncaughtExceptionHandler 方法

package com.abc.xyz;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.AsyncConfigurer;

@Configuration
public class AsyncConfig implements AsyncConfigurer {

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new MyAsyncUncaughtExceptionHandler();
    }
}

 4.线程调度配置

Spring boot 默认配置的线程池是ThreadPoolTaskExecutor

修改配置文件

spring.task.execution.pool.core-size=8
spring.task.execution.pool.max-size=16
spring.task.execution.pool.queue-capacity=100
spring.task.execution.pool.keep-alive=10s

spring.task.execution.pool.core-size # 核心线程数，默认为8
spring.task.execution.pool.max-size # 最大线程数，默认为无限大
spring.task.execution.pool.queue-capacity # 队列容量，默认为无限大
spring.task.execution.pool.keep-alive # 空闲的线程可以保留多少秒，默认为60。如果超过这个时间没有任务调度，则线程会被回收

5.自定义线程调度器

通过实现AsyncConfigurer接口来定义自己的线程调度器

修改 AsyncConfig

package com.abc.xyz;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@Configuration
public class AsyncConfig implements AsyncConfigurer {
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(10);
        executor.setMaxPoolSize(20);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix("my-executor-");
        executor.initialize();
        return executor;
    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new MyAsyncUncaughtExceptionHandler();
    }
}

重新启动，控制台输出

task before
2019-12-15 22:00:44.725 INFO 9204 --- [nio-8080-exec-1] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService
task2任务开始, timestamp=1576418444734, threadId=51, threadName=my-executor-1
task2任务结束, timestamp=1576418447736, threadId=51, threadName=my-executor-1
success
task after
执行时间3017
task1任务开始, timestamp=1576418447740, threadId=52, threadName=my-executor-2
task1任务结束, timestamp=1576418450740, threadId=52, threadName=my-executor-2

说明：

　　线程池的前缀改成了my-executor-

　　输出o.s.s.concurrent.ThreadPoolTaskExecutor，是因为没有指定异步执行的executor，在第一次执行的时候会进行初始化

6.多线程池

让线程池只做一件事，防止多个共用线程池出线抢占溢出情况

修改 AsyncConfig，添加task1Executor，task2Executor

package com.abc.xyz;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@Configuration
public class AsyncConfig implements AsyncConfigurer {
    @Bean
    public Executor task1Executor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(2);
        executor.setMaxPoolSize(3);
        executor.setQueueCapacity(10);
        executor.setThreadNamePrefix("task1-executor-");
        executor.initialize();
        return executor;
    }

    @Bean
    public Executor task2Executor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(2);
        executor.setMaxPoolSize(3);
        executor.setQueueCapacity(10);
        executor.setThreadNamePrefix("task2-executor-");
        executor.initialize();
        return executor;
    }

    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(1);
        executor.setMaxPoolSize(2);
        executor.setQueueCapacity(10);
        executor.setThreadNamePrefix("my-executor-");
        executor.initialize();
        return executor;
    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new MyAsyncUncaughtExceptionHandler();
    }
}

使用线程池

package com.abc.xyz;

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Component;

import java.util.concurrent.Future;

@Component
public class MyTask {

    @Async("task1Executor")
    public void task1() {
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task1任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task1任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());
    }

    @Async("task2Executor")
    public Future<String> task2() throws Exception{
        long timestamp = System.currentTimeMillis();
        Thread thread = Thread.currentThread();
        System.out.println("task2任务开始, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        try {
            Thread.sleep(3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        timestamp = System.currentTimeMillis();
        System.out.println("task2任务结束, timestamp=" + timestamp + ", threadId=" + thread.getId() + ", threadName=" + thread.getName());

        return new AsyncResult<>("success");
    }
}

重新启动，控制台输出

task before
task2任务开始, timestamp=1576419065314, threadId=52, threadName=task2-executor-1
task2任务结束, timestamp=1576419068315, threadId=52, threadName=task2-executor-1
success
task after
执行时间3052
task1任务开始, timestamp=1576419068354, threadId=53, threadName=task1-executor-1
task1任务结束, timestamp=1576419071356, threadId=53, threadName=task1-executor-1