    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
    015    package org.apache.tapestry5.tree;
    016
    017    import 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     */
    027    public 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    }