<input id="complex" value="hi" class="{required:true,minlength:3, maxlength:5,
messages:{required:'为什么不输入一点文字呢',minlength:'输入的太少了',maxlength:'输入那么多干嘛'}}" />

$().ready(function() {
 $("#form2").validate({
 rules: {
  password: {
  required: true,
  minlength: 5
  },
  confirm_password: {
  required: true,
  minlength: 5,
  equalTo: "#password"
  }
 },
 messages: {
  password: {
  required: "没有填写密码",
  minlength: jQuery.format("密码不能小于{0}个字符")
  },
  confirm_password: {
  required: "没有确认密码",
  minlength: "确认密码不能小于{0}个字符",
  equalTo: "两次输入密码不一致嘛"
  }
 }
 });
});

$("#form2").validate({
 rules: {
 funcvalidate: {
 required: function() {return $("#password").val()!=""; }
 }
 },
 messages: {
 funcvalidate: {
 required: "有密码的情况下必填"
 }
 }
});

email<input class="{validate:{required:true, email:true, 
messages:{required:'输入email地址', email:'你输入的不是有效的邮件地址'}}}"/>

$().ready(function() {
 $.metadata.setType("attr", "validate");
 $("#form1").validate();
});