001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019 020package org.apache.commons.compress.utils; 021 022import java.util.Iterator; 023import java.util.NoSuchElementException; 024import java.util.ServiceConfigurationError; 025import java.util.ServiceLoader; 026 027/** 028 * Iterates all services for a given class through the standard 029 * {@link ServiceLoader} mechanism. 030 * 031 * @param <E> 032 * The service to load 033 * @since 1.13 034 */ 035public class ServiceLoaderIterator<E> implements Iterator<E> { 036 037 private E nextServiceLoader; 038 private final Class<E> service; 039 private final Iterator<E> serviceLoaderIterator; 040 041 public ServiceLoaderIterator(final Class<E> service) { 042 this(service, ClassLoader.getSystemClassLoader()); 043 } 044 045 public ServiceLoaderIterator(final Class<E> service, final ClassLoader classLoader) { 046 this.service = service; 047 final ServiceLoader<E> serviceLoader = ServiceLoader.load(service, classLoader); 048 serviceLoaderIterator = serviceLoader.iterator(); 049 nextServiceLoader = null; 050 } 051 052 private boolean getNextServiceLoader() { 053 while (nextServiceLoader == null) { 054 try { 055 if (!serviceLoaderIterator.hasNext()) { 056 return false; 057 } 058 nextServiceLoader = serviceLoaderIterator.next(); 059 } catch (final ServiceConfigurationError e) { 060 if (e.getCause() instanceof SecurityException) { 061 // Ignore security exceptions 062 // TODO Log? 063 continue; 064 } 065 throw e; 066 } 067 } 068 return true; 069 } 070 071 @Override 072 public boolean hasNext() { 073 return getNextServiceLoader(); 074 } 075 076 @Override 077 public E next() { 078 if (!getNextServiceLoader()) { 079 throw new NoSuchElementException("No more elements for service " + service.getName()); 080 } 081 final E tempNext = nextServiceLoader; 082 nextServiceLoader = null; 083 return tempNext; 084 } 085 086 @Override 087 public void remove() { 088 throw new UnsupportedOperationException("service=" + service.getName()); 089 } 090 091}