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     * Used with {@link DefaultTreeModel} to define how to extract labels and child nodes from a value.
021     *
022     * @since 5.3
023     */
024    public interface TreeModelAdapter<T>
025    {
026        /**
027         * Determines if the value is a leaf or a (potential) container of children.
028         *
029         * @see TreeNode#isLeaf()
030         */
031        boolean isLeaf(T value);
032    
033        /**
034         * Returns true if the value has children (only invoked for non-leaf values).
035         *
036         * @see TreeNode#getHasChildren()
037         */
038        boolean hasChildren(T value);
039    
040        /**
041         * Returns the children, in the order they should be presented to the client.
042         * This should return the childen in the correct presentation or, or return null or an empty list.
043         *
044         * @see TreeNode#getChildren()
045         */
046        List<T> getChildren(T value);
047    
048        /**
049         * Returns a text label for the value, which may be presented to the client.
050         *
051         * @see TreeNode#getLabel()
052         */
053        String getLabel(T value);
054    }