Ajax的用户名异步验证案例

package com.dodi.servlets; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.dodi.dao.impl.UserDaoImpl; import com.dodi.pojo.User; /** * Servlet implementation class AjaxCheck */ @WebServlet("/check") public class AjaxCheck extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public AjaxCheck() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("进入ajax"); //返回xml到客户端 boolean flag=true; String message=""; UserDaoImpl u=new UserDaoImpl(); User user=u.selectByName(request.getParameter("uname")); if(user==null){ message="用户名可以使用"; }else{ flag=false; message="用户名已存在，请选择其他用户名"; } System.out.println(message); response.setContentType("text/xml;charset=utf-8"); PrintWriter out=response.getWriter(); response.setHeader("Cache-Control", "no-cache"); out.println("<?xml version='1.0' encoding='utf-8'?>"); out.println("<response>"); out.println("<passed>"+Boolean.toString(flag)+"</passed>"); out.println("<message>"+message+"</message>"); out.println("</response>"); out.close(); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }