1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.core.util;
18
19 import java.util.List;
20
21 import org.apache.logging.log4j.core.config.Configuration;
22 import org.apache.logging.log4j.core.config.ConfigurationListener;
23 import org.apache.logging.log4j.core.config.Reconfigurable;
24
25 /**
26 * Watches for changes in a Source and performs an action when it is modified.
27 *
28 * @see WatchManager
29 */
30 public interface Watcher {
31
32 String CATEGORY = "Watcher";
33 String ELEMENT_TYPE = "watcher";
34
35 /**
36 * Returns the list of listeners for this configuration.
37 * @return The list of listeners.
38 */
39 List<ConfigurationListener> getListeners();
40
41 /**
42 * Called when the configuration has been modified.
43 * @param source The location of the configuration that was modified.
44 */
45 void modified();
46
47 /**
48 * Periodically called to determine if the configuration has been modified.
49 * @return true if the configuration was modified, false otherwise.
50 */
51 boolean isModified();
52
53 /**
54 * Returns the time the source was last modified or 0 if it is not available.
55 * @return the time the soruce was last modified.
56 */
57 long getLastModified();
58
59 /**
60 * Called when the Watcher is registered.
61 * @param source the Source that is being watched.
62 */
63 void watching(Source source);
64
65 /**
66 * Returns the Source being monitored.
67 * @return the Source.
68 */
69 Source getSource();
70
71 /**
72 * Creates a new Watcher by copying the original and using the new Reconfigurable and listeners.
73 * @param reconfigurable The Reconfigurable.
74 * @param listeners the listeners.
75 * @param lastModifiedMillis The time the resource was last modified in milliseconds.
76 * @return A new Watcher.
77 */
78 Watcher newWatcher(Reconfigurable reconfigurable, List<ConfigurationListener> listeners, long lastModifiedMillis);
79 }