来自portlet的SpringMVC ActionMapping传递参数：ActionURL

Question

我想尝试从ActionMapping-Method上的POST-Form发送参数。 我的JSP代码：

<portlet:actionURL name="answer" var="answerUrl">
    <portlet:param name="answerValue" value="${answerValue}"/>
    <portlet:param name="typus" value="${typus}"/>
</portlet:actionURL>

<form id="question" class="" action="${answerQuestionUrl}" method="POST">

<div class="dropdown">
    <select name="dropdown" id="dropdown">
        <option value=""></option>
        <c:forEach items="${dropDownMap}" var="entry">
            <option value="${entry.key}">${entry.value}</option>
        </c:forEach>
    </select>       
<div class="clear">
    <div class="left"></div>
     <input type="image" name="submit" src="pic.png" class="operation-functions element-right" />
    <br class="clear">
</div>

从这个表格我必须从投递箱

接收选定的值

@ActionMapping(value = "answer")
    public void answerQuestion(PortletRequest request, ActionResponse response, @RequestParam String answer, @RequestParam String typus){
    }

但是两个参数“answer”和“typus”都是空的。 我如何通过ActionMapping和portlet传递选定值来自Droplet：actionUrl。

THX