| /* |
| * 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.tamaya.spisupport; |
| |
| import org.apache.tamaya.spi.ServiceContext; |
| |
| import javax.annotation.Priority; |
| import java.io.Serializable; |
| import java.util.Comparator; |
| |
| /** |
| * Comparator implementation for ordering services loaded based on their increasing priority values. |
| */ |
| public class PriorityServiceComparator implements Comparator<Object>, Serializable { |
| |
| private static final long serialVersionUID = 1L; |
| |
| private static final PriorityServiceComparator INSTANCE = new PriorityServiceComparator(); |
| |
| /** Singleton constructor. */ |
| private PriorityServiceComparator(){} |
| |
| /** |
| * Get the shared instance of the comparator. |
| * @return the shared instance, never null. |
| */ |
| public static PriorityServiceComparator getInstance(){ |
| return INSTANCE; |
| } |
| |
| @Override |
| public int compare(Object o1, Object o2) { |
| int prio = getPriority(o1) - getPriority(o2); |
| if (prio < 0) { |
| return 1; |
| } else if (prio > 0) { |
| return -1; |
| } else { |
| return o1.getClass().getSimpleName().compareTo(o2.getClass().getSimpleName()); |
| } |
| } |
| |
| /** |
| * Checks the given instance for a @Priority annotation. If present the annotation's createValue is evaluated. If no such |
| * annotation is present, a default priority {@code 1} is returned. |
| * |
| * @param o the instance, not {@code null}. |
| * @return a priority, by default 1. |
| */ |
| public static int getPriority(Object o) { |
| return getPriority(o.getClass()); |
| } |
| |
| /** |
| * Checks the given type optionally annotated with a @Priority. If present the annotation's createValue is evaluated. |
| * If no such annotation is present, a default priority {@code 1} is returned. |
| * |
| * @param type the type, not {@code null}. |
| * @return a priority, by default 1. |
| */ |
| @SuppressWarnings({ "rawtypes", "unchecked" }) |
| public static int getPriority(Class type) { |
| int prio = 1; |
| if(ServiceContext.PRIORITY_ANNOTATION_AVAILABLE) { |
| Priority priority = (Priority) type.getAnnotation(Priority.class); |
| if (priority != null) { |
| prio = priority.value(); |
| } |
| } |
| return prio; |
| } |
| } |