1 package org.apache.helix.store;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 /**
23 * Callback interface on property changes
24 * @param <T>
25 */
26 public interface PropertyChangeListener<T>
27 {
28 /**
29 * Callback function when there is a change in any property that starts with key
30 * It's upto the implementation to handle the following different cases 1) key
31 * is a simple key and does not have any children. PropertyStore.getProperty(key) must
32 * be used to retrieve the value; 2) key is a prefix and has children.
33 * PropertyStore.getPropertyNames(key) must be used to retrieve all the children keys.
34 * Its important to know that PropertyStore will not be able to provide the
35 * delta[old value,new value] or which child was added/deleted. The
36 * implementation must take care of the fact that there might be callback for
37 * every child thats added/deleted. General way applications handle this is
38 * keep a local cache of keys and compare against the latest keys.
39 *
40 * @param key
41 */
42 void onPropertyChange(String key);
43 }