The <ui:include> and <ui:param> tags are two tag handlers that can be used for accomplishing many kinds of tasks; as long as we keep in mind that tag handlers are efficient only when the view tree is built, we can exploit them for our benefit. For example, we can use them to generate a tree node structure as shown in the following screenshot:

In order to accomplish this task, we will spice up the <ui:include> and <ui:param> tags with a dash of JSTL (the <c:if> and <c:forEach> tag handlers) and recursivity.

First, we need a class that represents the abstractization of the tree node concept. Basically, a tree node representation is a hierarchical structure of labels that can be recursively traversed. Based on this, we can write a generic tree node class as shown in the following code:

public class GenericTreeNode {

  private final List<GenericTreeNode> descendants;
  private final String label;

 ...