在 JSTL 标签中检索 cookie 和数组值

问题描述

在检索我需要使用的 cookie 时:

While retrieving cookies I need to use:

<c:forEach items="${cookie}" var="currentCookie">
    ${currentCookie.value.name} </br>
</c:forEach>

但是，在使用自定义数组时，为什么我们需要跳过 .value 函数?

But, while using custom arrays, why we need to skip the .value function?

<c:forEach items="${myList}" var="myList">
    ${myList.name} </br>
</c:forEach>

Cookie 包含一个 .getValue 函数()，它以字符串格式返回 cookie 的内容，那么使用 currentCookie.value.name 是如何工作的?

Cookie contains a .getValue function() which returns the content of the cookie in string format, so how does using currentCookie.value.name work?

推荐答案

${cookie} 指向一个 Map 使用 cookie 名称作为映射键和 Cookie 对象作为映射值.在 中对 Map 的每次迭代都会给你一个 Map.Entry 返回 getKey() 和 getValue() 方法.您的困惑是 Cookie 对象又也有一个 getValue() 方法.

The ${cookie} points to a Map<String, Cookie> with the cookie name as map key and the Cookie object as map value. Every iteration over a Map in <c:forEach> gives you a Map.Entry back which in turn has getKey() and getValue() methods. Your confusion is that the Cookie object has in turn also a getValue() method.

<c:forEach items="${cookie}" var="currentCookie">
    Cookie name as map entry key: ${currentCookie.key}<br/>
    Cookie object as map entry value: ${currentCookie.value}<br/>
    Name property of Cookie object: ${currentCookie.value.name}<br/>
    Value property of Cookie object: ${currentCookie.value.value}<br/>
</c:forEach>

这是一个 Map 因为它允许您在事先知道名称的情况下轻松直接访问 cookie 值.下面的例子假设它是 cookieName:

It's a Map<String, Cookie> because it allows you easy direct access to cookie value when you already know the name beforehand. The below example assumes it to be cookieName:

${cookie.cookieName.value}

顺便说一下，您的列表示例无效.var 不应引用与列表本身相同的名称.

Your list example is by the way invalid. The var should not refer the same name as the list itself.

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