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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