function checkUsername(){ // 获得文件框值: var username = document.getElementById("username").value; // 1.创建异步交互对象 var xhr = createXmlHttp(); // 2.设置监听 xhr.onreadystatechange = function(){ if(xhr.readyState == 4){ if(xhr.status == 200){ document.getElementById("span1").innerHTML = xhr.responseText; } } } // 3.打开连接 xhr.open("GET","${pageContext.request.contextPath}/user_findByName.action?time="+new Date().getTime()+"&username="+username,true); // 4.发送 xhr.send(null); } function createXmlHttp(){ var xmlHttp; try{ // Firefox, Opera 8.0+, Safari xmlHttp=new XMLHttpRequest(); } catch (e){ try{// Internet Explorer xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e){ try{ xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); } catch (e){} } } return xmlHttp; } 

 public String findByName() throws IOException { // 调用Service进行查询: User existUser = userService.findByUsername(user.getUsername()); // 获得response对象,项页面输出: HttpServletResponse response = ServletActionContext.getResponse(); response.setContentType("text/html;charset=UTF-8"); // 判断 if (existUser != null) { // 查询到该用户:用户名已经存在 response.getWriter().println("用户名已经存在"); } else { // 没查询到该用户:用户名可以使用 response.getWriter().println("用户名可以使用"); } return NONE; } 

 private UserDao userDao; public void setUserDao(UserDao userDao) { this.userDao = userDao; } // 按用户名查询用户的方法: public User findByUsername(String username){ return userDao.findByUsername(username); } 

 public User findByUsername(String username){ String hql = "from User where username = ?"; List list = this.getHibernateTemplate().find(hql, username); if(list != null && list.size() > 0){ return list.get(0); } return null; } 

       org.hibernate.dialect.MySQLDialecttruetruefalseupdate  cn/itcast/shop/user/vo/User.hbm.xml       [html] view plain copy 在CODE上查看代码片派生到我的代码片     /WEB-INF/jsp/msg.jsp /WEB-INF/jsp/index.jsp /WEB-INF/jsp/regist.jsp/WEB-INF/jsp/regist.jsp/WEB-INF/jsp/login.jsp/WEB-INF/jsp/login.jspindexindex/WEB-INF/jsp/regist.jsp