Spring中注解方式的异步请求

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来源: 51数据库
2021-08-16

一、servlet3.0异步请求

@webservlet(value = "/async", asyncsupported = true)
public class helloasyncservlet extends httpservlet {

    @override
    protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
        //1、设置支持异步处理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();
                    //获取到异步的上下文
                    asynccontext asynccontext = req.getasynccontext();
                    startasync.complete();
                    servletresponse response = asynccontext.getresponse();
                    response.getwriter().write("hello async!");
                    system.out.println("副线程结束:" + thread.currentthread() + "==>" + system.currenttimemillis());
                } catch (exception e) {
                    e.printstacktrace();
                }

            }
        });
        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);
    }
}

打印结果：

二、springmvc的异步请求

返回callable

@controller
public class asynccontroller {

    @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>() {

            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 "async01";
            }
        };

        system.out.println("主线程结束:" + thread.currentthread() + "==>" + system.currenttimemillis());
        return callable;

    }
}

控制器返回callable
spring进行异步处理，将callable提交给taskexecutor，使用一个隔离的线程进行执行
dispatcherservlet和所有的filter退出web容器的线程，但是response保持打开状态
callable返回结果，spreingmvc将请求重新派发给容器，恢复之前的处理，callable返回值就是目标方法的返回值
根据callable返回的结果，springmvc继续进行视图渲染流程等(从收到请求到视图渲染)

输出结果：

返回deferredresult

模拟一个消息中间件

public class deferredresultqueue {

    private static queue<deferredresult<object>> queue = new concurrentlinkeddeque<deferredresult<object>>();
    

    public static void save(deferredresult<object> deferredresult){
        queue.add(deferredresult);
    }
    
    public static deferredresult<object> get(){
        return queue.poll();
    }
}

/createorder请求会暂时保存deferredresultqueue中，/create请求会获取deferredresultqueue中的请求，进行业务逻辑的处理并返回结果

@controller
public class asynccontroller {

    @responsebody
    @requestmapping("/createorder")
    public deferredresult<object> createorder(){
        deferredresult<object> deferredresult = new deferredresult<object>((long)3000,"create fail");

        deferredresultqueue.save(deferredresult);

        return deferredresult;
    }


    @responsebody
    @requestmapping("/create")
    public string create(){

        string order = uuid.randomuuid().tostring();
        deferredresult<object> deferredresult = deferredresultqueue.get();
        deferredresult.setresult(order);
        return "success:" + order;
    }
}

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