Spring Boot 基于DeferredResult的异步服

上一篇文章写了基于Servlet 的HTTP异步服务，这一章我们来说说基于DeferredResult的异步服务。

1. 在pom.xml中引入配置

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

2. 建立Service层接口

public interface PiceaService {
    //无返回参数方法
    void task() throws Exception;
    //有返回参数方法
    String task2() throws Exception;
}

3. 建立Service层实现
   Service层接口与实现，跟其他正常同步请求一样，没有差别。

@Service
public class PiceaServiceImpl implements PiceaService {

    @Override
    public void task() throws Exception {
        System.out.println("------------------------在看貂蝉，不要打扰--------------");
        Thread.sleep(1000);
    }

    @Override
    public String task2 () throws Exception {
        int k = 1;
        System.out.println("------------------------在看鱼，不要打扰--------------");
        Thread.sleep(1000);
        return (String.valueOf(k));
    }
}

4. 建立Contoller层方法
   这是重点和核心，首先要定义一个线程池来处理异步的任务。然后就是编写异步的调用方法。

@RestController
public class PiceaServletContoller {

    @Autowired
    private PiceaService piceaService;

    @RequestMapping("/deferredresult")
    public DeferredResult<String> deferredResult() throws Exception {
        System.out.println("控制层执行线程:" + Thread.currentThread().getName());
        //超时
        DeferredResult<String> deferredResult = new DeferredResult<String>(10*1000L);
        deferredResult.onTimeout(new Runnable() {
            @Override
            public void run() {
                System.out.println("异步线程执行超时");
                deferredResult.setResult("线程执行超时");
            }
        });
        deferredResult.onCompletion(new Runnable() {
            @Override
            public void run() {
                System.out.println("异步执行完毕");
            }
        });
        FIXED_THREAD_POOL.execute(new Runnable() {
            @Override
            public void run() {
                System.out.println("异步执行线程:" + Thread.currentThread().getName());
                try {
                    String str = piceaService.task2();
                    Thread.sleep(1000);
                    deferredResult.setResult("这是【异步】的请求返回: " + str);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
        return deferredResult;
    }

    /**
     * 线程池
     */
    public static ExecutorService FIXED_THREAD_POOL = Executors.newFixedThreadPool(10);
}

5. 测试结果及方法
   浏览器中访问http://localhost:2001/deferredresult测试结果。
   Spring-boot-async-deferredResult.png

其它注意

本文章样例：
工程名：spring-boot-async-deferredresult
GitHub：https://github.com/zzyjb/SpringBootLearning