Ajax初学体验（2）[检验用户名是否重复的完整实例]

发布时间：2020-12-16 00:41:55 所属栏目：百科来源：网络整理

导读：1、创建index.jsp页面如下： %@ page language="java" import="java.util.*" pageEncoding="UTF-8"%%String path = request.getContextPath();String basePath = request.getScheme() + "://"+ request.getServerName() + ":" + request.getServerPort()+ pa

1、创建index.jsp页面如下：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://"
			+ request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

<script type="text/javascript" src="js/index.js"></script>

</head>

<body>
	<form action="CheckUserName" method="post">
		用户名：<input type="text" id="userName" onblur="checkUserName(this.value)" />
		    <lable id="result"></lable><br/> 
		 密?码：<input type="password" name="password" />
	</form>
	<br/>
</body>
</html>

2、js文件如下：

function createAjax(){
	var ajax = null;
	try{
		ajax = new XMLHttpRequest();
	}catch(e1){
		var versions=['Microsoft.XMLHTTP','MSXML.XMLHTTP','Msxml2.XMLHTTP.7.0','Msxml2.XMLHTTP.6.0','Msxml2.XMLHTTP.5.0','Msxml2.XMLHTTP.4.0','MSXML2.XMLHTTP.3.0','MSXML2.XMLHTTP'];
		for(var i = 0;i<versions.length;i++){
			try{
				ajax = new ActiveXObject(versions[i]);
				break;
			}catch(ex){
				
			}
		}
	}
	return ajax;
}

function checkUserName(value){
	var ajax = new createAjax();
	ajax.open("GET","servlet/CheckUserName?userName="+value);
	
	ajax.onreadystatechange = function(){
		if(ajax.readyState==4&&ajax.status==200){
			document.getElementById("result").innerHTML = ajax.responseText;
		}
	}
	
	ajax.send();
}

3、逻辑处理的servlet

package edu.uestc.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CheckUserName extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public CheckUserName() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request,HttpServletResponse response)
			throws ServletException,IOException {
		//System.out.println("Do Get......");
		
		String username = request.getParameter("userName");
		//解决Get方法的乱码问题
		username = new String(username.getBytes("ISO-8859-1"),"UTF-8");
		System.out.println(username);
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		if ("zsz".equals(username)){
			out.println("用户名重复");
		}else{
			out.println("用户名可用");
		}
		out.flush();
		out.close();
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request,IOException {
		// Put your code here
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}

配置文件如下：

<servlet>  
    <servlet-name>CheckUserName</servlet-name>  
    <servlet-class>edu.uestc.servlet.CheckUserName</servlet-class>  
  </servlet>  
  
  <servlet-mapping>  
    <servlet-name>CheckUserName</servlet-name>  
    <url-pattern>/servlet/CheckUserName</url-pattern>  
  </servlet-mapping>

（编辑：李大同）

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