【下载文档:  Ajax——异步检查用户名是否存在示例.txt 】

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Ajax――异步检查用户名是否存在示例
在任何网站注册用户的时候，都会检查用户是否已经存在。很久以前的处理方式是将所有数据提交到服务器端进行验证，很显然这种方式的用户体验很不好；后来有了Ajax，有了异步交互，当用户输完用户名继续填写其他信息的时候，Ajax就将信息发到了服务器去检查该用户名是否已经被注册了，这样如果用户名已经存在，不用等用户将所有数据都提交就可以给出提示。采用这种方式大大改善了用户体验。 regist.jsp 复制代码 代码如下: <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

用户名:
密 码:

CheckServlet.java 复制代码 代码如下: public class CheckServlet extends HttpServlet { private static final long serialVersionUID = 1L; public static final String DBDRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver"; public static final String DBURL = "jdbc:sqlserver://localhost:1433;DatabaseName=bbs"; public static final String DBUSER = "sa"; public static final String DBPASS = "pass"; public CheckServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); response.setContentType("text/html"); Connection conn = null; PreparedStatement pst = null; ResultSet rs = null; PrintWriter out = response.getWriter(); String username = request.getParameter("usernaem"); try{ Class.forName(DBDRIVER); conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS); String sql = "select count(username) from user where username=?"; pst = conn.prepareStatement(sql); pst.setString(1,username); rs = pst.executeQuery(); if(rs.next()){ if(rs.getInt(1)>0){//用户名已经存在了 out.print("true"); }else{ out.print("false"); } } }catch(Exception e){ e.printStackTrace(); }finally{ try{ conn.close(); }catch(Exception e){ e.printStackTrace(); } } } }