Java 实现异步请求方式一：Servlet 方式

落日映苍穹つ 2023-06-25 03:21 36阅读 0赞

### 1、请求异步 ###

服务器端接受到请求后，首先释放掉容器分配的接受请求的主线程，于是其响应延后，异步的新线程，在完成业务运算后对客户端做出响应。简言之，增加了客户端对服务器请求的吞吐量。

### 2、代码示例 ###

package com.listen.demo.ctr;
    
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import javax.servlet.AsyncContext;
    import javax.servlet.AsyncEvent;
    import javax.servlet.AsyncListener;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import java.io.IOException;
    
    import static org.springframework.web.bind.annotation.RequestMethod.GET;
    
    /**
     * @author liuxd
     * @version 1.0
     * @date 2019-12-25 11:16
     */
    @Controller
    @RequestMapping("/api")
    @Slf4j
    public class IController {
    
        @RequestMapping(value = "/req1", method = GET)
        public void req1(HttpServletRequest request, HttpServletResponse response) {
            AsyncContext asyncContext = request.startAsync();
            //监听
            asyncContext.addListener(new AsyncListener() {
                @Override
                public void onStartAsync(AsyncEvent event) throws IOException {
                    log.info("新线程开始");
                }
    
                @Override
                public void onError(AsyncEvent event) throws IOException {
                    log.info("新线程程序异常：" + event.getThrowable());
                }
    
                @Override
                public void onTimeout(AsyncEvent event) throws IOException {
                    log.info("新线程请求超时");
                    //TODO
                }
    
                @Override
                public void onComplete(AsyncEvent event) throws IOException {
                    log.info("新线程结束");
                    //TODO
                }
            });
    
            //超时时间20秒
            asyncContext.setTimeout(20000);
            asyncContext.start(new Runnable() {
                @Override
                public void run() {
                    try {
                        //int a = 1/0;//测试异常
                        //Thread.sleep(30000);//测试超时
                        Thread.sleep(5000);
                        log.info("新线程名称：" + Thread.currentThread().getName());
    
                        response.setCharacterEncoding("utf-8");
                        response.setContentType("text/html;charset=UTF-8");
                        response.getWriter().println("异步请求响应信息");
    
                    } catch (Exception e) {
                        log.error("程序异常");
                        e.printStackTrace();
                    }
                    //异步请求结束通知
                    asyncContext.complete();
                }
            });
    
            //主线程执行完随即释放
            log.info("主线程名称：" + Thread.currentThread().getName());
        }
    
    }