springmvc checkbox标签隐藏value为on

jsp代码；

 课程：<c:forEach items="${courseList }" var="course01">
        <form:checkbox path="courseIdList" value="${course01.courseId}"/>${course01.courseName}
        </c:forEach>                             
        <br/>

        源码：
         课程：
        <input id="courseIdList1" name="courseIdList" type="checkbox" value="1"/><input type="hidden" name="_courseIdList" value="on"/>语文

        <input id="courseIdList2" name="courseIdList" type="checkbox" value="2"/><input type="hidden" name="_courseIdList" value="on"/>数学

        <input id="courseIdList3" name="courseIdList" type="checkbox" value="3"/><input type="hidden" name="_courseIdList" value="on"/>美术

        <br/> 

http://lavasoft.blog.51cto.com/62575/1407213/