BootstrapValidator验证用户名已存在（ajax）

<link rel="stylesheet" href="<%=request.getContextPath() %>/css/bootstrap.min.css" rel="external nofollow" />
<link rel="stylesheet" href="<%=request.getContextPath() %>/css/bootstrapValidator.min.css" rel="external nofollow" />

<script src="<%=request.getContextPath() %>/js/jquery.min.js"></script>
<script src="<%=request.getContextPath() %>/js/bootstrap.min.js"></script> 
<script src="<%=request.getContextPath() %>/js/bootstrapValidator.min.js"></script>

<form id="registerForm" action="<%=request.getContextPath() %>/UserServlet" method="post">
 <input type="hidden" name="method" value="register"/>
 <div class="form-group">
  <label>用户名</label>
  <input type="text" class="form-control" name="userName" placeholder="用户名由2-12位字符组成" />
 </div>

 <div class="form-group">
  <label>邮箱</label>
  <input type="text" class="form-control" name="userEmail" placeholder="邮箱" />
 </div>

 <div class="form-group">
  <label>密码</label>
  <input type="password" class="form-control" name="userPassword" placeholder="密码由6-10位字母数字组成" />
 </div>

 <div class="form-group">
  <label>确认密码</label>
  <input type="password" class="form-control" name="confirmUserPassword" placeholder="输入密码" />
 </div>

 <div class="form-group">
  <button type="submit" class="btn btn-primary">注册</button>
  <input type="reset" class="btn btn-primary" value="重置">
 </div>
</form>

<script type="text/javascript">
 $(function() {
  $('#registerForm').bootstrapValidator({
   message: 'This value is not valid',
   feedbackIcons: {
    valid: 'glyphicon glyphicon-ok',
    invalid: 'glyphicon glyphicon-remove',
    validating: 'glyphicon glyphicon-refresh'
   },
   fields: {
    userName: {
     message: 'The username is not valid',
     validators: {
      notEmpty: {
       message: '用户名不能为空'
      },
      stringLength: {
       min: 2,
       max: 12,
       message: '用户名由2-12位字符组成'
      },
      threshold: 2,//有2字符以上才发送ajax请求
      remote: {//ajax验证。server result:{"valid",true or false} 
       url: "/ImageShare/UserServlet",
       message: '用户名已存在,请重新输入',
       delay: 1000,//ajax刷新的时间是1秒一次
       type: 'POST',
       //自定义提交数据，默认值提交当前input value
       data: function(validator) {
       return {
        userName : $("input[name=userName]").val(),
         method : "checkUserName"//UserServlet判断调用方法关键字。
        };
       }
      }
     }
    },
    userEmail: {
     validators: {
      notEmpty: {
       message: '邮箱不能为空'
      },
      emailAddress: {
       message: '输入不是有效的电子邮件地址'
      }
     }
    },
    userPassword: {
     validators: {
      notEmpty: {
       message: '密码不能为空'
      },
      stringLength: {
       min: 6,
       max: 10,
       message: '密码由6-10位字符组成'
      },
      identical: {
       field: 'confirmUserPassword',
       message: '密码输入不一致'
      }
     }
    },
    confirmUserPassword: {
     validators: {
      notEmpty: {
       message: '密码不能为空'
      },
      stringLength: {
       min: 6,
       max: 10,
       message: '密码由6-10位字符组成'
      },
      identical: {
       field: 'userPassword',
       message: '密码输入不一致'
      }
     }
    }
   }
  });
 });
</script>

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 request.setCharacterEncoding("UTF-8");
 //0、获取method判断执行操作
 String method = request.getParameter("method");
 if ("checkUserName".equals(method)) {
 //验证用户名是否已存在
 checkUserName(request,response);
 }
}

//根据用户名称查询，检查用户名称的唯一性（用户注册）
public void checkUserName(HttpServletRequest request, HttpServletResponse response) throws IOException{
 response.setCharacterEncoding("UTF-8");
 //返回json数据，格式为{"valid",true} 表示合法，验证通过。{"valid":false} 表示不合法，验证不通过
 String jsonResult = "";
 String userName = request.getParameter("userName");
 //去数据进行唯一性确认
 if (userName!=null) {
 //服务层service调用数据库访问层dao中的searchUserName方法。
 boolean b = UserServiceImpl.searchUserName(userName);
 if (b) {
 //如果名称存在
 jsonResult = "{\"valid\":false}";
 }else{
 //如果该名称不存在
 jsonResult = "{\"valid\":true}";
 }
 } else {
 jsonResult = "{\"valid\":false}";
 }
 //response把jsonResult打到前台
 response.getWriter().write(jsonResult);
}