23、spring注解学习——servlet3.0异步和spring的异步

servlet3.0异步: 

加上asyncSupported=true使支持异步

package com.atguigu.servlet;

import java.io.IOException;

import javax.servlet.AsyncContext;
import javax.servlet.ServletException;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(value="/async",asyncSupported=true)
public class HelloAsyncServlet extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1、支持异步处理asyncSupported=true
        //2、开启异步模式
        System.out.println("主线程开始。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
        AsyncContext startAsync = req.startAsync();
        
        //3、业务逻辑进行异步处理;开始异步处理
        startAsync.start(new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println("副线程开始。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
                    sayHello();
                    startAsync.complete();
                    //获取到异步上下文
                    AsyncContext asyncContext = req.getAsyncContext();
                    //4、获取响应
                    ServletResponse response = asyncContext.getResponse();
                    response.getWriter().write("hello async...");
                    System.out.println("副线程结束。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
                } catch (Exception e) {
                }
            }
        });        
        System.out.println("主线程结束。。。"+Thread.currentThread()+"==>"+System.currentTimeMillis());
    }

    public void sayHello() throws Exception{
        System.out.println(Thread.currentThread()+" processing...");
        Thread.sleep(3000);
    }
}

执行结果如下:

 如上截图可以看出servlet3.0的异步和servlet用的是同一个线程池

springmvc的异步（spring会给副线程再建一个线程池）

package com.atguigu.controller;

import java.util.UUID;
import java.util.concurrent.Callable;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.context.request.async.DeferredResult;

import com.atguigu.service.DeferredResultQueue;


@Controller
public class AsyncController {
    
    
    @ResponseBody
    @RequestMapping("/createOrder")
    public DeferredResult<Object> createOrder(){
        DeferredResult<Object> deferredResult = new DeferredResult<>((long)3000, "create fail...");
            
        DeferredResultQueue.save(deferredResult);
        
        return deferredResult;
    }
    
    
    @ResponseBody
    @RequestMapping("/create")
    public String create(){
        //创建订单
        String order = UUID.randomUUID().toString();
        DeferredResult<Object> deferredResult = DeferredResultQueue.get();
        deferredResult.setResult(order);
        return "success===>"+order;
    }
    
    /**
     * 1、控制器返回Callable
     * 2、Spring异步处理，将Callable 提交到 TaskExecutor 使用一个隔离的线程进行执行
     * 3、DispatcherServlet和所有的Filter退出web容器的线程，但是response 保持打开状态；
     * 4、Callable返回结果，SpringMVC将请求重新派发给容器，恢复之前的处理；
     * 5、根据Callable返回的结果。SpringMVC继续进行视图渲染流程等（从收请求-视图渲染）。
     * 
     * preHandle.../springmvc-annotation/async01
        主线程开始...Thread[http-bio-8081-exec-3,5,main]==>1513932494700
        主线程结束...Thread[http-bio-8081-exec-3,5,main]==>1513932494700
        =========DispatcherServlet及所有的Filter退出线程============================
        
        ================等待Callable执行==========
        副线程开始...Thread[MvcAsync1,5,main]==>1513932494707
        副线程开始...Thread[MvcAsync1,5,main]==>1513932496708
        ================Callable执行完成==========
        
        ================再次收到之前重发过来的请求========
        preHandle.../springmvc-annotation/async01
        postHandle...（Callable的之前的返回值就是目标方法的返回值）
        afterCompletion...
        
        异步的拦截器:
            1）、原生API的AsyncListener
            2）、SpringMVC：实现AsyncHandlerInterceptor；
     * @return
     */
    @ResponseBody
    @RequestMapping("/async01")
    public Callable<String> async01(){
        System.out.println("主线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
        
        Callable<String> callable = new Callable<String>() {
            @Override
            public String call() throws Exception {
                System.out.println("副线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
                Thread.sleep(2000);
                System.out.println("副线程开始..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
                return "Callable<String> async01()";
            }
        };
        
        System.out.println("主线程结束..."+Thread.currentThread()+"==>"+System.currentTimeMillis());
        return callable;
    }

}

执行结果如下:

发现拦截器的preHandle执行了两次（原因即为：spring主线程结束后会再次访问该路径，从而继续执行副线程，如最后的图）

 

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