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1：注册表单
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>get方式请求数据，不要传参数</title> </head> <body> <input type="text" name="username" id="username" onblur="textAjax()"> <span id="mydiv" ></span> <input type="password" name="password"> <input type="button" value="测试是否可以注册" onclick="textAjax()"> <script type="text/javascript"> function textAjax() { //获取xmlHttpRequest对象(ajax引擎) var xmlhttprequest; if (window.XMLHttpRequest) { xmlhttprequest=new XMLHttpRequest(); //code for IE7+, Firefox, Chrome, Opera, Safari } else{ xmlhttprequest=new ActiveXObject("Microsoft.XMLHTTP"); //code for IE6, IE5 } //alert(xmlhttprequest);//说明获取对象成功 //与服务器建立连接,默认是true,异步，可以不写 xmlhttprequest.open("POST","${pageContext.request.contextPath}/sevletDemo2?time="+new Date().getTime(),true); //向服务器发送请求数据，没有为null,传递数据是post请求的 如username=jack&password=123 //post提交时候，如果不是表单要加请求头，，因为servlet要request.getParams(),如果是表单就不要默认ectype就是 //在send()前加context-type xmlhttprequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded"); var username=document.getElementById("username").value; xmlhttprequest.send("username="+username); xmlhttprequest.onreadystatechange=function(){ //alert(xmlhttprequest.readyState);4表示成功 //alert(xmlhttprequest.status);200表示成功 if(xmlhttprequest.readyState==4){ if(xmlhttprequest.status==200){ var mydiv=document.getElementById("mydiv"); mydiv.innerHTML=xmlhttprequest.responseText; } } } } </script> </body> </html>
2：请求的 servlet对客户端提交的数据进行校验
public class sevletDemo2 extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); String username=request.getParameter("username"); PrintWriter writer=response.getWriter(); System.out.println(username); if("jack".equals(username)) { writer.write("用户名已存在"); } else { writer.write("可以注册"); } }
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原文地址：http://www.cnblogs.com/linhong/p/4489096.html
