    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    }