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
018package org.apache.logging.log4j.util;
019
020import org.apache.logging.log4j.message.Message;
021
022/**
023 * Classes implementing this interface know how to supply {@link Message}s.
024 *
025 * <p>This is a <a href="https://docs.oracle.com/javase/8/docs/api/java/util/function/package-summary.html">functional
026 * interface</a> intended to support lambda expressions in log4j 2.
027 *
028 * <p>Implementors are free to cache values or return a new or distinct value each time the supplier is invoked.
029 *
030 * <p><strong>DEPRECATED:</strong> this class should not normally be used outside a Java 8+ lambda syntax. Instead,
031 * {@link Supplier Supplier<Message>} should be used as an anonymous class. Both this and {@link Supplier} will be
032 * removed in 3.0.
033 * </p>
034 *
035 * @since 2.4
036 */
037public interface MessageSupplier {
038
039    /**
040     * Gets a Message.
041     *
042     * @return a Message
043     */
044    Message get();
045}