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 */ 017package org.apache.logging.log4j.util; 018 019import java.io.IOException; 020import java.net.URL; 021import java.util.Collection; 022import java.util.Enumeration; 023import java.util.HashSet; 024import java.util.Properties; 025import java.util.concurrent.locks.Lock; 026import java.util.concurrent.locks.ReentrantLock; 027 028import org.apache.logging.log4j.Logger; 029import org.apache.logging.log4j.spi.Provider; 030import org.apache.logging.log4j.status.StatusLogger; 031 032/** 033 * <em>Consider this class private.</em> Utility class for Log4j {@link Provider}s. When integrating with an application 034 * container framework, any Log4j Providers not accessible through standard classpath scanning should 035 * {@link #loadProvider(java.net.URL, ClassLoader)} a classpath accordingly. 036 */ 037public final class ProviderUtil { 038 039 /** 040 * Resource name for a Log4j 2 provider properties file. 041 */ 042 protected static final String PROVIDER_RESOURCE = "META-INF/log4j-provider.properties"; 043 044 /** 045 * Loaded providers. 046 */ 047 protected static final Collection<Provider> PROVIDERS = new HashSet<>(); 048 049 /** 050 * Guards the ProviderUtil singleton instance from lazy initialization. This is primarily used for OSGi support. 051 * 052 * @since 2.1 053 */ 054 protected static final Lock STARTUP_LOCK = new ReentrantLock(); 055 056 private static final String API_VERSION = "Log4jAPIVersion"; 057 private static final String[] COMPATIBLE_API_VERSIONS = {"2.0.0", "2.1.0", "2.2.0", "2.3.0", "2.4.0", "2.5.0", "2.6.0"}; 058 private static final Logger LOGGER = StatusLogger.getLogger(); 059 060 // STARTUP_LOCK guards INSTANCE for lazy initialization; this allows the OSGi Activator to pause the startup and 061 // wait for a Provider to be installed. See LOG4J2-373 062 private static volatile ProviderUtil instance; 063 064 private ProviderUtil() { 065 for (final LoaderUtil.UrlResource resource : LoaderUtil.findUrlResources(PROVIDER_RESOURCE)) { 066 loadProvider(resource.getUrl(), resource.getClassLoader()); 067 } 068 } 069 070 /** 071 * Loads an individual Provider implementation. This method is really only useful for the OSGi bundle activator and 072 * this class itself. 073 * 074 * @param url the URL to the provider properties file 075 * @param cl the ClassLoader to load the provider classes with 076 */ 077 protected static void loadProvider(final URL url, final ClassLoader cl) { 078 try { 079 final Properties props = PropertiesUtil.loadClose(url.openStream(), url); 080 if (validVersion(props.getProperty(API_VERSION))) { 081 final Provider provider = new Provider(props, url, cl); 082 PROVIDERS.add(provider); 083 LOGGER.debug("Loaded Provider {}", provider); 084 } 085 } catch (final IOException e) { 086 LOGGER.error("Unable to open {}", url, e); 087 } 088 } 089 090 /** 091 * @deprecated Use {@link #loadProvider(java.net.URL, ClassLoader)} instead. Will be removed in 3.0. 092 */ 093 @Deprecated 094 protected static void loadProviders(final Enumeration<URL> urls, final ClassLoader cl) { 095 if (urls != null) { 096 while (urls.hasMoreElements()) { 097 loadProvider(urls.nextElement(), cl); 098 } 099 } 100 } 101 102 public static Iterable<Provider> getProviders() { 103 lazyInit(); 104 return PROVIDERS; 105 } 106 107 public static boolean hasProviders() { 108 lazyInit(); 109 return !PROVIDERS.isEmpty(); 110 } 111 112 /** 113 * Lazily initializes the ProviderUtil singleton. 114 * 115 * @since 2.1 116 */ 117 protected static void lazyInit() { 118 // noinspection DoubleCheckedLocking 119 if (instance == null) { 120 try { 121 STARTUP_LOCK.lockInterruptibly(); 122 try { 123 if (instance == null) { 124 instance = new ProviderUtil(); 125 } 126 } finally { 127 STARTUP_LOCK.unlock(); 128 } 129 } catch (final InterruptedException e) { 130 LOGGER.fatal("Interrupted before Log4j Providers could be loaded.", e); 131 Thread.currentThread().interrupt(); 132 } 133 } 134 } 135 136 public static ClassLoader findClassLoader() { 137 return LoaderUtil.getThreadContextClassLoader(); 138 } 139 140 private static boolean validVersion(final String version) { 141 for (final String v : COMPATIBLE_API_VERSIONS) { 142 if (version.startsWith(v)) { 143 return true; 144 } 145 } 146 return false; 147 } 148}