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;
18
19 import java.io.Serializable;
20
21 /**
22 * Appends {@link LogEvent}s. An Appender can contain a {@link Layout} if applicable as well
23 * as an {@link ErrorHandler}. Typical Appender implementations coordinate with an
24 * implementation of {@link org.apache.logging.log4j.core.appender.AbstractManager} to handle external resources
25 * such as streams, connections, and other shared state. As Appenders are plugins, concrete implementations need to
26 * be annotated with {@link org.apache.logging.log4j.core.config.plugins.Plugin} and need to provide a static
27 * factory method annotated with {@link org.apache.logging.log4j.core.config.plugins.PluginFactory}.
28 *
29 * <p>Most core plugins are written using a related Manager class that handle the actual task of serializing a
30 * {@link LogEvent} to some output location. For instance, many Appenders can take
31 * advantage of the {@link org.apache.logging.log4j.core.appender.OutputStreamManager} class.</p>
32 *
33 * <p>It is recommended that Appenders don't do any heavy lifting since there can be many instances of the class
34 * being used at any given time. When resources require locking (e.g., through {@link java.nio.channels.FileLock}),
35 * it is important to isolate synchronized code to prevent concurrency issues.</p>
36 */
37 public interface Appender extends LifeCycle {
38
39 /**
40 * Main {@linkplain org.apache.logging.log4j.core.config.plugins.Plugin#elementType() plugin element type} for
41 * Appender plugins.
42 *
43 * @since 2.6
44 */
45 String ELEMENT_TYPE = "appender";
46
47 /**
48 * Logs a LogEvent using whatever logic this Appender wishes to use. It is typically recommended to use a
49 * bridge pattern not only for the benefits from decoupling an Appender from its implementation, but it is also
50 * handy for sharing resources which may require some form of locking.
51 *
52 * @param event The LogEvent.
53 */
54 void append(LogEvent event);
55
56
57 /**
58 * Gets the name of this Appender.
59 *
60 * @return name, may be null.
61 */
62 String getName();
63
64 /**
65 * Returns the Layout used by this Appender if applicable.
66 *
67 * @return the Layout for this Appender or {@code null} if none is configured.
68 */
69 Layout<? extends Serializable> getLayout();
70
71 /**
72 * Some Appenders need to propagate exceptions back to the application. When {@code ignoreExceptions} is
73 * {@code false} the AppenderControl will allow the exception to percolate.
74 *
75 * @return {@code true} if exceptions will be logged but not thrown, {@code false} otherwise.
76 */
77 boolean ignoreExceptions();
78
79 /**
80 * Gets the {@link ErrorHandler} used for handling exceptions.
81 *
82 * @return the ErrorHandler for handling exceptions.
83 */
84 ErrorHandler getHandler();
85
86 /**
87 * Sets the {@link ErrorHandler} used for handling exceptions.
88 *
89 * @param handler the ErrorHandler to use for handling exceptions.
90 */
91 void setHandler(ErrorHandler handler);
92 }