Ajax验证数据唯一性
js:
function checkLoginName() {var loginName = document.myform.loginName.value;if (loginName == "" || loginName == null) { alert('用户名不能为空！'); return false;} else { var url = "action.do?method=checkLoginName&loginName=" + loginName; send(url); // document.myform.action = "action.do?method=checkLoginName"; // document.myform.submit();}}var xmlHttp;function createXmlHttp() {if (window.XMLHttpRequest) { xmlHttp = new XMLHttpRequest();} else if (window.ActiveXObject) { xmlHttp = new ActiveXObject("MIcrosoft.XMLHttp");}}function send(url) {createXmlHttp();xmlHttp.open("GET", url, true);xmlHttp.onreadystatechange = processRequest;xmlHttp.send(null);}function processRequest() {if (xmlHttp.readyState == 4) { if (xmlHttp.status == 200) { var myfont = document.getElementById("name"); while (myfont.hasChildNodes()) { myfont.removeChild(myfont.firstChild); } var text = document.createTextNode(); text.nodeValue = xmlHttp.responseText; myfont.appendChild(text); }}}public ActionForward checkLoginName(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { LoginDao dao=new LoginDao(); String loginName=request.getParameter("loginName"); loginName=new String(loginName.getBytes("ISO-8859-1"),"UTF-8"); System.out.println(loginName); int num=dao.check(loginName); if(num==0){ response.getWriter().println("可用"); response.getWriter().flush(); }else{ response.getWriter().println("已经使用"); response.getWriter().flush(); } return null;}public int check(String loginName){ Session ss=HibernateSessionFactory.getSession(); ss.beginTransaction(); Query q=ss.createQuery("select loginName from Login where loginName='"+loginName+"'"); List list=q.list(); ss.getTransaction().commit(); ss.close(); return list.size();}<tr> <td width="100" align="right"> 用户名: </td> <td align="left"> <input type="text" name="loginName" />  <input type="button" value="检查用户名" onclick="checkLoginName()"> <font color="red" size="2px" id="name"></font></td> </tr>