001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core;
018
019import java.io.Serializable;
020
021/**
022 * Appends log events. An Appender can contain a {@link org.apache.logging.log4j.core.Layout} if applicable as well
023 * as an {@link org.apache.logging.log4j.core.ErrorHandler}. Typical Appender implementations coordinate with an
024 * implementation of {@link org.apache.logging.log4j.core.appender.AbstractManager} to handle external resources
025 * such as streams, connections, and other shared state. As Appenders are plugins, concrete implementations need to
026 * be annotated with {@link org.apache.logging.log4j.core.config.plugins.Plugin} and need to provide a static
027 * factory method annotated with {@link org.apache.logging.log4j.core.config.plugins.PluginFactory}.
028 *
029 * <p>Most core plugins are written using a related Manager class that handle the actual task of serializing a
030 * {@link org.apache.logging.log4j.core.LogEvent} to some output location. For instance, many Appenders can take
031 * advantage of the {@link org.apache.logging.log4j.core.appender.OutputStreamManager} class.</p>
032 *
033 * <p>It is recommended that Appenders don't do any heavy lifting since there can be many instances of the class
034 * being used at any given time. When resources require locking (e.g., through {@link java.nio.channels.FileLock}),
035 * it is important to isolate synchronized code to prevent concurrency issues.</p>
036 */
037public interface Appender extends LifeCycle {
038
039    /**
040     * Logs a LogEvent using whatever logic this Appender wishes to use. It is typically recommended to use a
041     * bridge pattern not only for the benefits from decoupling an Appender from its implementation, but it is also
042     * handy for sharing resources which may require some form of locking.
043     *
044     * @param event The LogEvent.
045     */
046    void append(LogEvent event);
047
048
049    /**
050     * Get the name of this Appender.
051     *
052     * @return name, may be null.
053     */
054    String getName();
055
056    /**
057     * Returns the Layout used by this Appender if applicable.
058     *
059     * @return the Layout for this Appender or {@code null} if none is configured.
060     */
061    Layout<? extends Serializable> getLayout();
062
063    /**
064     * Some Appenders need to propagate exceptions back to the application. When {@code ignoreExceptions} is
065     * {@code false} the AppenderControl will allow the exception to percolate.
066     *
067     * @return {@code true} if exceptions will be logged but not thrown, {@code false} otherwise.
068     */
069    boolean ignoreExceptions();
070
071    ErrorHandler getHandler();
072
073    void setHandler(ErrorHandler handler);
074}