JSTL Hashmap和动态密钥 [英] JSTL Hashmap and dynamic key

问题描述

在页面的doGet上，我设置了一些默认属性.

On my doGet of the page I setup some default attributes.

    private static final CategoryFactory cf = CategoryFactory.getInstance();

public static void setupHeader(HttpServletRequest req) {
    ArrayList<String> catagories = cf.getPrimaryCategories();
    Map<String, ArrayList<String>> categoryMap = cf.getCategoryMap();
    User user = UserUtils.getUserSession(req);

    req.setAttribute("catagories", catagories);
    req.setAttribute("categoryMap", categoryMap);
    req.setAttribute("isAdmin", UserUtils.isAdmin(user));
    if (user != null) {
        req.setAttribute("orderCount", user.getOrderCount(false));
        req.setAttribute("unreadMessageCount", user.getUnreadMessageCount());
        req.setAttribute("cartTotal", user.getShoppingCart().getTotal());
    }
}

然后在我的JSP页面上，我试图根据类别(即Map的键)使用categoryMap.

Then on my JSP page I'm trying to work with the categoryMap based on the catagories which are the keys from Map.

<c:forEach var="cata" items="${catagories}">
<li class="dropdown-submenu"><a tabindex="-1" href="#"><c:out value="${cata}" /></a>
<ul class="dropdown-menu" role="menu">

    <c:forEach var="secCategories" items="${categoryMap['cata']}">
        <c:forEach var="second" items="${secCategories}">
            <li role="presentation"><a role="menuitem"
                href="/browse?type="${fn:replace(second, ' ','+')}"><c:out
                        value="${second}" /></a></li>
        </c:forEach>
    </c:forEach>

</ul></li>
</c:forEach>

我得到的错误是

警告:嵌套在javax.servlet.ServletException中: javax.servlet.jsp.JspException:javax.el.PropertyNotFoundException: 找不到媒体资源[Aerial&课堂上的起重设备 java.lang.String:javax.el.PropertyNotFoundException:找不到 财产[航空类java.lang.String

WARNING: Nested in javax.servlet.ServletException: javax.servlet.jsp.JspException: javax.el.PropertyNotFoundException: Could not find property [Aerial & Lifting Equipment in class java.lang.String: javax.el.PropertyNotFoundException: Could not find property [Aerial & Lifting Equipment in class java.lang.String

其中"[航空和起重设备""是变量类别中的第一个关键字，并设置为新变量$ {cata}.由于此操作不起作用，因此我缺少有关如何正确传递动态密钥的一些信息.

Where "[Aerial & Lifting Equipment" is the first key from the variable categories and set as the new variable ${cata}. As this is not working, I'm missing something on how to pass the dynamic key properly.

解决方案
这解决了我的问题，我设置了之前忘记的属性类型，为了便于使用，我将ArrayList更改为String [].

SOLUTION
This fixed my issue, I set the attribute types which I forgot before, and for ease of use I changed the ArrayList to a String[].

<%@attribute name="user" required="true" type="com.entity.User"%>
<%@attribute name="catagories" required="true" type="java.lang.String[]"%>
<%@attribute name="categoryMap" required="true" type="java.util.Map"%>

<c:forEach var="cata" items="${catagories}">
<li class="dropdown-submenu"><a tabindex="-1" href="#"><c:out value="${cata}" /></a>
<ul class="dropdown-menu" role="menu">
<c:forEach var="secCategories" items="${categoryMap[cata]}">
    <c:forEach var="second" items="${secCategories}">
        <li role="presentation"><a role="menuitem"
            href="/browse?type="${fn:replace(second, ' ','+')}"><c:out
                    value="${second}" /></a></li>
    </c:forEach>
</c:forEach>
</ul></li>
</c:forEach>

推荐答案

你会生自己的气，但是....

You're gonna be mad at yourself, but ....

<c:forEach var="secCategories" items="${categoryMap['cata']}">

应该是

<c:forEach var="secCategories" items="${categoryMap[cata]}">

您不希望文字字符串"cata"成为键，而您希望cata page属性的值成为键. :)

You don't want the literal string "cata" being the key, you want the value of the cata page property being the key. :)

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