/** ajax登录，并jquery md5 加密密码 */
function loginsubmit() {
 var salt=$("#username").val(); 
    var pwd=$("#password").val();  
    var md5Pwd=$.md5(pwd+salt);
   
    var validateCode=$("#validateCode").val();
    var rememberMe=$("#rememberMe").val();
   
 data="username="+  salt
  + "&password=" + md5Pwd
  + "&validateCode=" + validateCode
  + "&rememberMe=" + rememberMe;

 $.ajax({
     type: "POST",
     url: "loginsubmit",
     dataType:'html',
     data: data,
     contentType:"application/x-www-form-urlencoded;charset=UTF-8",
     success: function(msg){
      if(msg=="ok") {
       location.href = "index";
      }else if (msg=="errorcode"){
       alert("验证码无效！");
      }
     },
     error: function (XMLHttpRequest, textStatus, errorThrown) {
               alert(XMLHttpRequest.status);
               alert(XMLHttpRequest.readyState);
               alert(textStatus);
           }
 });
}

以上代码中url为 loginsubmit.html 去掉".html"即可提交 ，后台代码用的@ResponseBody注解