解析ajax实现无刷新验证用户名是否存在_AJAX教程

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推荐：揭秘Ajax 及其入门基础
一、白话Ajax的原理这个可以从 C/S 和 B/S 的原理说起。Windows操作系统的诞生，为单机通信提供了很大的支持，程序设计也从早期DOS的单任务单用户向网络的分布式应用过度。C/S提供的客户/服务器编程模式为网络应用提供了一个有效的通信手段。浏览器与Web服

实现用的是jdbc+jsp+servlet,数据库用的是mysql

表就2个字段

实现原理获得text的值后,通过调用servlet查询数据库里是否存在,在通过xml传到前台

OperationName.java

response.setContentType("text/xml;charset=UTF-8")这句很重要,没有他前台获得不到xml,之前做的时候没有加

所以前台获得不到xml

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

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

public class OperationName extends HttpServlet
{

/** *//**
* Constructor of the object.
*/
public OperationName()
{
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
{
String names = request.getParameter("names");
Collection students = null;
Connection con = null;
Statement st = null;
ResultSet rs = null;
try
{
Class.forName("org.gjt.mm.mysql.Driver");
con = DriverManager.getConnection("jdbc:mysql:"+
"//127.0.0.1:3306/test?useUnicode=true&characterEncoding=GBK","root","eetrust");
st = con.createStatement();
rs = st.executeQuery("select count(*) from test where name='"+names+"'");
StringBuffer result = new StringBuffer();
result.append("<OperationNames>");
System.out.println(result);
while(rs.next())
{
int num = rs.getInt(1);
result.append("<OperationName>" + num + "</OperationName>");
}
result.append("</OperationNames>");
String responseHtml = result.toString();
response.setCharacterEncoding( "UTF-8");
response.setContentType("text/xml;charset=UTF-8");
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
response.getWriter().write(responseHtml);
}catch(Exception e)
{
e.printStackTrace();
}finally
{
try
{
rs.close();
st.close();
con.close();
}catch(Exception e)
{
e.printStackTrace();
}
}
}

/** *//**
* 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, HttpServletResponse response) throws ServletException, IOException
{
this.doGet(request,response);
}

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

}
index.jsp

ajax("servlet/OperationName?names=" + newOperationName + "&form=form1");"&form=form1"可去掉

<%@ page language="java" contentType="text/html;charset=GBK"%>
<%
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 'MyJsp.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 language="javascript">

</Script>
</head>

<body>
<form action="index.jsp" >
<table>
<tr>
<td>
<input type="text" name="names" value="" Onblur="aaa()">
</td>
</tr>
<tr>
<TD bgcolor="#EEEEEE" id="ShowInfo">
asdas
</TD>
</tr>
<tr>

</tr>
</table>
</form>
</body>
</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>OperationName</servlet-name>
<servlet-class>servlet.OperationName</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>OperationName</servlet-name>
<url-pattern>/servlet/OperationName</url-pattern>
</servlet-mapping>
</web-app>

分享：揭秘Ajax 及其入门基础(续)
四、常见Ajax编程框架既然上述Ajax框架已经能工作了，为什么还有那么多的框架呢？随着页面的复杂，可能需要书写大量的Javascript脚本来对页面中的DOM对象进行控制，工作量和复杂度会大大增加。Ajax编程框架通常利用面向对象的方法，对一些基本的对象和行为

来源：模板无忧/所属分类：AJAX教程/更新时间：2010-01-09

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