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Ajax技术入门

AjaxServletJavaScriptJavaEEWeb 
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写了个ajax验证用户名是否可用的小例子，记在这，以备后查。


在Eclipse中新建一个dynamic web project，新建两个servlet，一个名为ClassicServlet，使用传统方式进行用户名验证，另一个名为AjaxServlet，使用Ajax方式进行用户名验证。代码如下：

ClassicServlet.java：

 

package com.dcr.javascript.ajax01;

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 ClassicServlet 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 out = response.getWriter();
		try{
			String name = request.getParameter("name");
			if ("hello".equals(name)){
				out.println("用户名" + name + "已经被使用，请重新填写！<a href='javascript:history.go(-1)'>返回</a>");	
			}else{
				out.println("用户名" + name + "可以使用！<a href='javascript:history.go(-1)'>返回</a>");
			}
		}finally{
			out.close();
		}
	}

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

 

AjaxServlet.java

 

package com.dcr.javascript.ajax01;

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 AjaxServlet 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 out = response.getWriter();
		try{
			String name = request.getParameter("name");
			if ("hello".equals(name)){
				out.println("用户名" + name + "已经被使用，请重新填写！");	
			}else{
				out.println("用户名" + name + "可以使用！");
			}
		}finally{
			out.close();
		}
	}

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

 这两个servlet对应的html为classic.html,和ajax.html:

 

classic.html

 

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>传统方式</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
<form action="Classic" method="get">
	<input id="name" name="name" />
	<input type="submit" value="验证用户名">
</form>
</body>
</html>

 

ajax.html

 

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Ajax方式</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript" src="../js/ajax01/ajax.js"></script>
</head>
<body>
<input id="name" />
<input type="button" value="验证用户名" onclick="check()" />
<div id="message"></div>
</body>
</html>
 

ajax.js:

 

var XmlHttpResquest;

function check(){
	if(window.XMLHttpRequest){
		XmlHttpResquest = new XMLHttpRequest();
		if(XmlHttpResquest.overrideMimeType){
			XmlHttpResquest.overrideMimeType("text/xml");
		}
	}else if(window.ActiveXObject){
		var activexName = ["MSXML2.XMLHTTP.6.0","MSXML2.XMLHTTP.5.0","MSXML2.XMLHTTP.4.0",
			"MSXML2.XMLHTTP.3.0","MSXML2.XMLHTTP","Miscrosoft.XMLHTTP"];
		for(var i = 0;i < activexName.length;i++){
			try{
				XmlHttpResquest = new ActiveXObject(activexName[i]);
				break;
			}catch(e){
				continue;
			}
		}
	}
	if(XmlHttpResquest == undefined || XmlHttpResquest == null){
		alert("当前浏览器不支持创建XMLHttpResuest对象，请更换浏览器！");
	}
	XmlHttpResquest.onreadystatechange = callback;
	XmlHttpResquest.open("GET","../ajax01/Ajax?name=" + document.getElementById("name").value,true);
	XmlHttpResquest.send(null);
}
function callback()
{
	if(XmlHttpResquest.readyState == 4){
		if(XmlHttpResquest.status == 200){
			document.getElementById("message").innerHTML = XmlHttpResquest.responseText;
		}
	}
}

 

web.xml:

 

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
	<display-name>javascript</display-name>
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
	</welcome-file-list>
	<servlet>
		<servlet-name>Classic</servlet-name>
		<servlet-class>com.dcr.javascript.ajax01.ClassicServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>Classic</servlet-name>
		<url-pattern>/ajax01/Classic</url-pattern>
	</servlet-mapping>
	<servlet>
		<description></description>
		<display-name>Ajax</display-name>
		<servlet-name>Ajax</servlet-name>
		<servlet-class>com.dcr.javascript.ajax01.AjaxServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>Ajax</servlet-name>
		<url-pattern>/ajax01/Ajax</url-pattern>
	</servlet-mapping>
</web-app>

 

这样已经很全了，就不再上传源码了。

 

本来想截个项目结构图的，但是不知道怎么插入到文章内容中去，暂且作罢。

 

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