spring通过一个注解关键字 @Async 表明一段代码将放入异步线程代码块里面运行。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;

import java.util.concurrent.CompletableFuture;

@Service
public class MyService {
    private static final Logger logger = LoggerFactory.getLogger(MyService.class);

    public MyService() {
    }

    //这部分代码将放入到一个线程内完成。
    @Async
    public CompletableFuture<Integer> sum(int a, int b) throws InterruptedException {
        logger.info("计算: " + a + " + " + b);
        int s = a + b;
        Thread.sleep(3 * 1000);
        logger.info("计算: " + a + " + " + b + " 结束");
        return CompletableFuture.completedFuture(s);
    }
}

上面代码示例计算两数之和，假设很耗时，所以放到线程里面执行。

定义一个runner：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

import java.util.concurrent.CompletableFuture;

@Component
public class MyAppRunner implements CommandLineRunner {
    private static final Logger logger = LoggerFactory.getLogger(MyAppRunner.class);
    private final MyService myService;

    public MyAppRunner(MyService service) {
        this.myService = service;
    }

    @Override
    public void run(String... args) throws Exception {
        logger.info("-" + System.currentTimeMillis());

        CompletableFuture s1 = myService.sum(1, 2);
        CompletableFuture s2 = myService.sum(3, 4);
        CompletableFuture s3 = myService.sum(5, 6);
        CompletableFuture s4 = myService.sum(7, 8);

        //CompletableFuture.allOf(s1, s2, s3, s4).join();

        logger.info("--" + System.currentTimeMillis());

        logger.info("1,2--> " + s1.get());
        logger.info("3,4--> " + s2.get());
        logger.info("5,6--> " + s3.get());
        logger.info("7,8--> " + s4.get());
    }
}

在spring的application里面关闭main()函数里面的线程池，取而代之由自己定义的一个线程池执行线程任务：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@SpringBootApplication
@EnableAsync
public class SpringAsyncApplication {

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

    @Bean
    public Executor taskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(10);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(500);
        executor.setThreadNamePrefix("phil-thread:");
        executor.initialize();
        return executor;
    }
}

运行日志输出（截取部分）：

:02:59.815  INFO 37044 --- [           main] c.e.spring_async.SpringAsyncApplication  : Started SpringAsyncApplication in 1.556 seconds (JVM running for 2.012)
:02:59.817  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : -1642158179816
:02:59.821  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : --1642158179820
:02:59.827  INFO 37044 --- [  phil-thread:1] com.example.spring_async.MyService       : 计算: 1 + 2
:02:59.827  INFO 37044 --- [  phil-thread:3] com.example.spring_async.MyService       : 计算: 5 + 6
:02:59.827  INFO 37044 --- [  phil-thread:2] com.example.spring_async.MyService       : 计算: 3 + 4
:02:59.827  INFO 37044 --- [  phil-thread:4] com.example.spring_async.MyService       : 计算: 7 + 8
:03:02.832  INFO 37044 --- [  phil-thread:2] com.example.spring_async.MyService       : 计算: 3 + 4 结束
:03:02.832  INFO 37044 --- [  phil-thread:4] com.example.spring_async.MyService       : 计算: 7 + 8 结束
:03:02.832  INFO 37044 --- [  phil-thread:1] com.example.spring_async.MyService       : 计算: 1 + 2 结束
:03:02.832  INFO 37044 --- [  phil-thread:3] com.example.spring_async.MyService       : 计算: 5 + 6 结束
:03:02.832  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : 1,2--> 3
:03:02.832  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : 3,4--> 7
:03:02.832  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : 5,6--> 11
:03:02.832  INFO 37044 --- [           main] com.example.spring_async.MyAppRunner     : 7,8--> 15