ajax中的同步和异步

 

 

ajax中的同步和异步
ajax的本质就是，发送http请求的工作交给js中的XMLHttpRequest对象去做
同步和异步的区别
简而言之：异步不阻塞后面代码的执行,同步会阻塞后面代码的执行

package com.jiongmeng.ajax;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * 测试同步和异步的区别
 */
@WebServlet("/asynchronous")
public class Asynchronous extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter pw = response.getWriter();
		double randomNumber = Math.random();
		try {
			//故意睡眠3秒，模拟网络慢的情况
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("随机数：" + randomNumber);
		pw.print("随机数：" + randomNumber);
		pw.flush();
		pw.close();
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

	@Override
	public void init(ServletConfig config) throws ServletException {

	}

}