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     */
017    package org.apache.logging.log4j.core;
018    
019    import java.io.Serializable;
020    
021    /**
022     * Appends {@link LogEvent}s. An Appender can contain a {@link Layout} if applicable as well
023     * as an {@link 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 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     */
037    public 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        /**
072         * Gets the {@link ErrorHandler} used for handling exceptions.
073         *
074         * @return the ErrorHandler for handling exceptions.
075         */
076        ErrorHandler getHandler();
077    
078        /**
079         * Sets the {@link ErrorHandler} used for handling exceptions.
080         *
081         * @param handler the ErrorHandler to use for handling exceptions.
082         */
083        void setHandler(ErrorHandler handler);
084    }