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    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       * Logs a LogEvent using whatever logic this Appender wishes to use. It is typically recommended to use a
    41       * bridge pattern not only for the benefits from decoupling an Appender from its implementation, but it is also
    42       * handy for sharing resources which may require some form of locking.
    43       *
    44       * @param event The LogEvent.
    45       */
    46      void append(LogEvent event);
    47
    48
    49      /**
    50       * Get the name of this Appender.
    51       *
    52       * @return name, may be null.
    53       */
    54      String getName();
    55
    56      /**
    57       * Returns the Layout used by this Appender if applicable.
    58       *
    59       * @return the Layout for this Appender or {@code null} if none is configured.
    60       */
    61      Layout<? extends Serializable> getLayout();
    62
    63      /**
    64       * Some Appenders need to propagate exceptions back to the application. When {@code ignoreExceptions} is
    65       * {@code false} the AppenderControl will allow the exception to percolate.
    66       *
    67       * @return {@code true} if exceptions will be logged but not thrown, {@code false} otherwise.
    68       */
    69      boolean ignoreExceptions();
    70
    71      /**
    72       * Gets the {@link ErrorHandler} used for handling exceptions.
    73       *
    74       * @return the ErrorHandler for handling exceptions.
    75       */
    76      ErrorHandler getHandler();
    77
    78      /**
    79       * Sets the {@link ErrorHandler} used for handling exceptions.
    80       *
    81       * @param handler the ErrorHandler to use for handling exceptions.
    82       */
    83      void setHandler(ErrorHandler handler);
    84  }