    001// Copyright 2011 The Apache Software Foundation
    002//
    003// Licensed under the Apache License, Version 2.0 (the "License");
    004// you may not use this file except in compliance with the License.
    005// You may obtain a copy of the License at
    006//
    007// http://www.apache.org/licenses/LICENSE-2.0
    008//
    009// Unless required by applicable law or agreed to in writing, software
    010// distributed under the License is distributed on an "AS IS" BASIS,
    011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012// See the License for the specific language governing permissions and
    013// limitations under the License.
    014
    015package org.apache.tapestry5.tree;
    016
    017import java.util.List;
    018
    019/**
    020 * A node within a {@link TreeModel}. In a {@link DefaultTreeModel}, most of the node's information
    021 * comes via the {@link TreeModelAdapter}.
    022 *
    023 * @param <T>
    024 *            type of node
    025 * @since 5.3
    026 */
    027public interface TreeNode<T>
    028{
    029    /**
    030     * Returns a string Id for the node that uniquely identifies it.
    031     *
    032     * @return unique string identifying the node
    033     * @see TreeModel#getById(String)
    034     */
    035    String getId();
    036
    037    /** Returns the value represented by this node. */
    038    T getValue();
    039
    040    /**
    041     * If true, then this node is a leaf node, which never has children (i.e., a file). If false, the node
    042     * may have children (i.e., a folder).
    043     *
    044     * @return true for leaf nodes, false for folder nodes
    045     * @see TreeModelAdapter#isLeaf(Object)
    046     */
    047    boolean isLeaf();
    048
    049    /**
    050     * Returns true if this non-leaf node has child nodes. This will not be invoked for leaf nodes.
    051     *
    052     * @see TreeModelAdapter#hasChildren(Object)
    053     */
    054    boolean getHasChildren();
    055
    056    /**
    057     * Returns the actual children of this non-leaf node, as additional nodes.
    058     *
    059     * @see TreeModelAdapter#getChildren(Object)
    060     */
    061    List<TreeNode<T>> getChildren();
    062
    063    // TODO: Some way to influence the rendered output (i.e., to display different icons based on
    064    // file type).
    065
    066    /**
    067     * Returns a textual label for the node. Not all UIs will make use of the label, but default UIs will.
    068     *
    069     * @see TreeModelAdapter#getLabel(Object)
    070     */
    071    public String getLabel();
    072}