javaScript中ajax入门

ajax的本质就是，发送http请求的工作交给js中的XMLHttpRequest对象去做！

ajax中，最关键的一句话就是var xhr = new XMLHttpRequest(); 

 

 

 ajax01.html代码如下：

ajax知识
ajax的本质就是，发送http请求的工作交给js中的XMLHttpRequest对象去做
用户名




	

		用户名
	
	

		邮箱
	
	

		
	
	

package com.jiongmeng.ajax;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import java.util.Vector;

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;

/**
 * 使用ajax检测用户名是否存在
 */
@WebServlet("/UserNameExist")
public class UserNameExist extends HttpServlet {
	private static final long serialVersionUID = 1L;

	List userNames;

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter pw = response.getWriter();
		String userName = request.getParameter("userName");
		boolean exist = userNames.contains(userName);
		request.setAttribute("exist", exist);
		System.out.println("userName = " + userName);
		try {
			// 模拟网络慢的情况
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
//		String webUrl = request.getContextPath();
//		 request.getRequestDispatcher("/userNameExist.jsp").forward(request, response);
		// response.sendRedirect(webUrl + "/userNameExist.jsp");
//		pw.write(exist + "");
		pw.print(exist);
		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 {
		userNames = new Vector();
		userNames.add("zhangsan");
		userNames.add("lisi");
		userNames.add("wangwu");
		userNames.add("zhaoliu");
	}

}

package com.jiongmeng.ajax;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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;

/**
 * 获取客户端提交的数据
 */
@WebServlet("/ajaxData")
public class AjaxData 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();
		Enumeration parameterNames = request.getParameterNames();
		StringBuffer sb = new StringBuffer();
		while(parameterNames.hasMoreElements()){
			String parameterName = parameterNames.nextElement();
			String parameterValue = request.getParameter(parameterName);
			System.out.println(parameterName + "=" + parameterValue);
			sb.append(parameterName + "=" + parameterValue + ";");
		}
		try {
			// 模拟网络慢的情况
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(sb.toString());
		pw.print(sb.toString());
		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 {

	}

}

 完！