/**
* Copyright (c) 2005-2012 https://github.com/zhangkaitao
*
* Licensed under the Apache License, Version 2.0 (the "License");
*/
package com.sishuok.chapter3.web.servlet.dispatch;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 分派到自己，此时需要一个flag判断当前需要启动异步，还是进行同步处理
* <p>User: Zhang Kaitao
* <p>Date: 13-7-18 下午3:46
* <p>Version: 1.0
*/
@WebServlet(name = "dispatchServlet3", urlPatterns = "/dispatch3", asyncSupported = true)
public class DispatchServlet3 extends HttpServlet {
@Override
protected void doGet(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {
if(req.getAttribute("ok") == null) {
System.out.println("===before start async:" + req.isAsyncStarted());
final AsyncContext asyncContext = req.startAsync();
System.out.println("===after start async:" + req.isAsyncStarted());
asyncContext.setTimeout(10L * 1000);
asyncContext.addListener(new AsyncListener() {
@Override
public void onComplete(final AsyncEvent event) throws IOException {
System.out.println("=====async complete");
}
@Override
public void onTimeout(final AsyncEvent event) throws IOException {
System.out.println("=====async timeout");
}
@Override
public void onError(final AsyncEvent event) throws IOException {
System.out.println("=====async error");
}
@Override
public void onStartAsync(final AsyncEvent event) throws IOException {
}
});
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(3L * 1000);
} catch (InterruptedException e) {
}
req.setAttribute("ok", "true");
req.setAttribute("msg", "success");
asyncContext.dispatch();
System.out.println("===after dispatch before handle:" + req.isAsyncStarted());
}
}).start();
return;
} else {
throw new RuntimeException("出错了");
//如果抛出异常，容器负责最后调用asyncContext.complete()
/**具体请参考{@link javax.servlet.AsyncContext#dispatch}的javadoc，而且一定要看*/
/**
* 在javadoc中有如下一段，意思就是如果抛出异常，需要回调 AsyncListener#onError但实际jetty实现是没有回调的
* <p>Any errors or exceptions that may occur during the execution
* of this method must be caught and handled by the container, as
* follows:
* <ol>
* <li>Invoke, at their {@link AsyncListener#onError onError} method, all
* {@link AsyncListener} instances registered with the ServletRequest
* for which this AsyncContext was created, and make the caught
* <tt>Throwable</tt> available via {@link AsyncEvent#getThrowable}.</li>
*/
}
}
}