JSTL - 使用forEach迭代用户定义的类 [英] JSTL - Using forEach to iterate over a user-defined class

问题描述

我需要将哪些方法添加到自定义Java类中，以便我可以遍历其中一个成员中的项目？我找不到关于JSTL forEach标签实际如何工作的任何规范，所以我不确定如何实现它。

What methods do I need to add to a custom Java class so that I can iterate over the items in one of its members? I couldn't find any specifications about how the JSTL forEach tag actually works so I'm not sure how to implement this.

例如，如果我做了一个通用的 ProjectSet我和我想在JSP视图中使用以下标记：

For example, if I made a generic "ProjectSet" class and I woud like to use the following markup in the JSP view:

<c:forEach items="${projectset}" var="project">
...
</c:forEach>

基本类文件：

public class ProjectSet {
    private ArrayList<Project> projects;
    public ProjectSet() {
        this.projects = new ArrayList<Project>();
    }
    // .. iteration methods ??
}

我是否必须实现任何接口，如PHP的 ArrayAccess 或 Iterator 以使其正常工作？

Is there any interface that I must implement like PHP's ArrayAccess or Iterator in order for this to work?

编辑：不直接访问ArrayList本身，因为我可能会使用泛型使用某种类的Set类，而JSP视图不应该知道类的内部工作原理。

Without directly accessing the ArrayList itself, because I will likely be using some sort of Set class using generics, and the JSP view shouldn't have to know about the inner workings of the class.

推荐答案

Iterable接口提供此功能：

The Iterable interface provides this functionality:

public class ProjectSet implements Iterable<Project> {
    private ArrayList<Project> projects;
    public ProjectSet() {
        this.projects = new ArrayList<Project>();
    }

    // .. iteration methods ??
   @Override
   public Iterator<Project> iterator() {
       return projects.iterator();
   }
}

您可以根据需要更换迭代器逻辑。

You can exchange the iterator logic as you need.

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