jQuery Validator插件-无验证

我知道这很简单(无论如何，根据插件页面)

I know this suppose to be simple (according to the plugin page anyway)

但是我试图使用该插件没有成功，这是我的表格:

But I'm trying to use the plugin with no success, here's my form:

<form id="mongoForm">
        <label for="skip">skip:</label> <input type="text" id="skip"
            style="width: 70px">
        <p />
        limit: <span id="limitLable" style="border: 0">1</span>
        <div id="limit" style="width: 250px"></div>
        <p />
        <label for="collection">collection: </label> <input type="text"
            id="collection">
        <p />
        <label for="sort">sort: </label> <input type="text" id="sort">
        <p />
        <label for="type">type: </label><select id="type">
            <option value="find" selected="selected">find</option>
            <option value="count">count</option>
        </select>
        <p />
        <label for="query">query: </label>
        <textarea rows="10" cols="80" id="query"></textarea>
        <input type="submit" value="execute" id="execute">
    </form>

和我的jquery脚本:

and my jquery script:

$(document).ready(function() {
    $.validator.addMethod("validJson", function(value, element) {
        try {
            var val = $.parseJSON(value);
            return true;
        } catch (e) {
            return false;
        }

    }, "Invalid JSON string");
    $("#mongoForm").validate({
        rules : {
            collection : {
                required : true
            },
            query : {
                validJson : true
            }
        },
        submitHandler : function(form) {
            queryServer();
        }
    });

但是，验证无法正常进行. 如果我在输入中添加class ="required"，则它适用于自定义验证，但不适用于我的自定义validJson方法.但这不能解决我的问题，因为某些字段不是必需的，我只需要验证可选值即可.

But, the validation is not working. If I add a class="required" to the inputs, it works for custom validations, but not for my custom validJson method. But this does not solve my problem as some fields are not required I just need to validate optional values

请问有什么想法吗?