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 package org.apache.logging.log4j.util; 018 019 import org.apache.logging.log4j.Logger; 020 import org.apache.logging.log4j.spi.Provider; 021 import org.apache.logging.log4j.status.StatusLogger; 022 023 import java.io.IOException; 024 import java.net.URL; 025 import java.util.ArrayList; 026 import java.util.Enumeration; 027 import java.util.Iterator; 028 import java.util.List; 029 import java.util.Properties; 030 031 /** 032 * 033 */ 034 public final class ProviderUtil { 035 036 private static final String PROVIDER_RESOURCE = "META-INF/log4j-provider.properties"; 037 private static final String API_VERSION = "Log4jAPIVersion"; 038 039 private static final String[] COMPATIBLE_API_VERSIONS = { 040 "2.0.0" 041 }; 042 043 private static final Logger LOGGER = StatusLogger.getLogger(); 044 045 private static final List<Provider> PROVIDERS = new ArrayList<Provider>(); 046 047 private ProviderUtil() { 048 } 049 050 static { 051 final ClassLoader cl = findClassLoader(); 052 Enumeration<URL> enumResources = null; 053 try { 054 enumResources = cl.getResources(PROVIDER_RESOURCE); 055 } catch (final IOException e) { 056 LOGGER.fatal("Unable to locate " + PROVIDER_RESOURCE, e); 057 } 058 059 if (enumResources != null) { 060 while (enumResources.hasMoreElements()) { 061 final Properties props = new Properties(); 062 final URL url = enumResources.nextElement(); 063 try { 064 props.load(url.openStream()); 065 } catch (final IOException ioe) { 066 LOGGER.error("Unable to read " + url.toString(), ioe); 067 } 068 if (!validVersion(props.getProperty(API_VERSION))) { 069 continue; 070 } 071 PROVIDERS.add(new Provider(props, url)); 072 } 073 } 074 } 075 076 public static Iterator<Provider> getProviders() { 077 return PROVIDERS.iterator(); 078 } 079 080 public static boolean hasProviders() { 081 return PROVIDERS.size() > 0; 082 } 083 084 public static ClassLoader findClassLoader() { 085 ClassLoader cl; 086 if (System.getSecurityManager() == null) { 087 cl = Thread.currentThread().getContextClassLoader(); 088 } else { 089 cl = java.security.AccessController.doPrivileged( 090 new java.security.PrivilegedAction<ClassLoader>() { 091 @Override 092 public ClassLoader run() { 093 return Thread.currentThread().getContextClassLoader(); 094 } 095 } 096 ); 097 } 098 if (cl == null) { 099 cl = ProviderUtil.class.getClassLoader(); 100 } 101 102 return cl; 103 } 104 105 private static boolean validVersion(final String version) { 106 for (final String v : COMPATIBLE_API_VERSIONS) { 107 if (version.startsWith(v)) { 108 return true; 109 } 110 } 111 return false; 112 } 113 }