| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache license, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the license for the specific language governing permissions and |
| * limitations under the license. |
| */ |
| package org.apache.logging.log4j.core.config; |
| |
| import java.io.Serializable; |
| import java.util.Comparator; |
| import java.util.Objects; |
| |
| /** |
| * Comparator for classes annotated with {@link Order}. |
| * |
| * @since 2.1 |
| */ |
| public class OrderComparator implements Comparator<Class<?>>, Serializable { |
| |
| private static final long serialVersionUID = 1L; |
| private static final Comparator<Class<?>> INSTANCE = new OrderComparator(); |
| |
| /** |
| * Returns a singleton instance of this class. |
| * |
| * @return the singleton for this class. |
| */ |
| public static Comparator<Class<?>> getInstance() { |
| return INSTANCE; |
| } |
| |
| @Override |
| public int compare(final Class<?> lhs, final Class<?> rhs) { |
| final Order lhsOrder = Objects.requireNonNull(lhs, "lhs").getAnnotation(Order.class); |
| final Order rhsOrder = Objects.requireNonNull(rhs, "rhs").getAnnotation(Order.class); |
| if (lhsOrder == null && rhsOrder == null) { |
| // both unannotated means equal priority |
| return 0; |
| } |
| // if only one class is @Order-annotated, then prefer that one |
| if (rhsOrder == null) { |
| return -1; |
| } |
| if (lhsOrder == null) { |
| return 1; |
| } |
| // larger value means higher priority |
| return Integer.signum(rhsOrder.value() - lhsOrder.value()); |
| } |
| } |