使用Ajax验证用户是否可以注册

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1．Java代码如下:package com.eduask;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//测试用户名在服务器中的测试;public class Demo2 extends HttpServlet{@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {resp.setContentType("text/html;charset=utf-8");String name=req.getParameter("name1");name=new String(name.getBytes("ISO8859-1"),"utf-8");if("tom".equals(name)){resp.getWriter().write("<font color=red>该用户已存在！</font>");}else{resp.getWriter().write("<font color=blue>该用户可以注册！</font>");}}}2.demo2.jsp代码如下:<body>请输入用户名: <input id="input1" type="text" name="name1"><span id="span1"></span><script type="text/JavaScript" language="javascript">var input1=document.getElementById("input1");input1.onblur=function(){var xhr=getXhr();xhr.onreadystatechange=function(){if(xhr.readyState==4){if(xhr.status==200){var msg=xhr.responseText;var span1=document.getElementById("span1");span1.innerHTML=msg;}}}xhr.open("get","/ajax/Demo2?name1="+input1.value,true);xhr.send(null);}function getXhr(){var xml;if(window.XMLHttpRequest){xml=new XMLHttpRequest();} else{xml=new ActiveXObject("microsoft,xmlhttp");}return xml;}</script>3.web.xml配置文件如下:<!-- demo2 --><servlet><servlet-name>Demo2</servlet-name><servlet-class>com.eduask.Demo2</servlet-class></servlet><servlet-mapping><servlet-name>Demo2</servlet-name><url-pattern>/Demo2</url-pattern></servlet-mapping>
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