<%@ page language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "/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" οnblur="textAjax()"><span id="mydiv" ></span><input type="password" name="password"><input type="button" value="测试是否可以注册" οnclick="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-typexmlhttprequest.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>1：注册表单
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");}}
