JSTL打印嵌套对象 [英] JSTL Printing Nested Objects

问题描述

如何在JSP页面的地图中打印嵌套对象/属性的值？

How does one go about printing the values of a nested object/property in a map on a JSP page?

<c:foreach items="${survey}" var="survey">

    <c:out value="${survey.value}" />

</c:foreach>

所以让我们说Survey有一个名为Questions（这是另一个对象）的属性，我想打印问题（survey.questions.getId（）或survey.questions.getTitle（）），foreach语句的外观如何？

So let's say Survey has a property called Questions (which is another object) and I want to print those questions (survey.questions.getId() or survey.questions.getTitle()), how would that foreach statement look?

编辑：SURVEY是一个地图而不是收集

SURVEY is a map and not a collection

推荐答案

如果您的嵌套属性是单个对象实例，则只需直接引用它，如：

If your nested property is a single object instance, you just reference it directly, like:

<c:forEach var="surveyItem" items="${surveys}">
    ${surveyItem.title} <!-- You can use the c:out if you really want to -->
</c:forEach>

假设您收集了 Survey 对象绑定到调查属性，每个调查有一个标题。它将打印每个调查的标题。

That assumes that you have a collection of Survey objects bound to the surveys attribute, and that each Survey has a title. It will print the title of each survey.

如果您的嵌套属性是对象的集合，那么您可以使用 forEach 循环来迭代它们，就像在你的例子中

If your nested property is a collection of objects, then you use a forEach loop to iterate them, just like in your example.

<c:forEach var="question" items="${survey.questions}">
    ${question.title} 
</c:forEach>

这将打印每个问题的标题假设您有一个绑定到调查属性的调查对象，而调查对象具有问题对象作为一个字段的集合（使用适当的getter方法，即 getQuestions（））。

That will print the title of each Question, assuming that you have a single Survey object bound to the survey attribute, and that the Survey object has a collection of Question objects as a field (with an appropriate getter method, i.e. getQuestions()).

您还可以使用嵌套循环，如：

You can also have nested loops, like:

<c:forEach var="surveyItem" items="${surveys}">
    ${surveyItem.title}
    <c:forEach var="question" items="${surveyItem.questions}">
        ${question.title} 
    </c:forEach>
</c:forEach>

这将打印每个调查的标题以及每个调查中的每个问题的标题。

That will print the title of every Survey along with the title of each Question in each Survey.

如果由于某种原因决定通过地图，您可以：

And if for some reason you decide to pass a Map, you can do:

<c:forEach var="entry" items="${surveyMap}">
    Map Key:  ${entry.key}
    Map Value:  ${entry.value}
    Nested Property:  ${entry.value.title}
    Nested Collection:
    <c:forEach var="question" items="${entry.value.questions}">
        ${question.title}
    </c:forEach>
</c:forEach>

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