我在修改员工信息的时候，向employee_update.jsp页面发送了数据如下：

@RequestMapping("/to_update")
public String toUpdate(@RequestParam String sn, Map<String ,Object> map){
    map.put("employee",employeeBiz.getBySn(sn));
    //查出所有的部门、职务发到前台以供选择
    map.put("departments",departmentBiz.getAll());
    map.put("posts", Contant.getPosts());
    return "employee_update";
}

在页面上使用select标签配置<c:foreach>，却没法显示出来所有的部门项、职位项

这是jsp页面部分代码：

<div class="section row">
        <div class="col-md-6">
            <label for="sn" class="field select">
                <select id="post" name="post" class="gui-input">
                    <c:forEach items="posts" var="post">
                        <option value="${post}">${post}</option>
                    </c:forEach>
                </select>
                <i class="arrow double"></i>
            </label>
        </div>
        <div class="col-md-6">
            <label for="post" class="field select">
                <select id="departmentSn" name="departmentSn" class="gui-input">
                    <c:forEach items="departments" var="dept">
                        <option value="${dept.sn}">${dept.name}</option>
                    </c:forEach>
                </select>
                <i class="arrow double"></i>
            </label>
        </div>
    </div>

    <div class="panel-footer text-right">
        <button type="submit" class="button"> 保存 </button>
        <button type="button" class="button" onclick="javascript:window.history.go(-1);"> 返回 </button>
    </div>
</div>

JSP的isELIgnored="false"也设置过了，那还有可能是哪里出问题了？