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 018package org.apache.log4j.helpers; 019 020import java.net.URL; 021import java.lang.reflect.Method; 022import java.lang.reflect.InvocationTargetException; 023import java.io.InterruptedIOException; 024 025 026/** 027 Load resources (or images) from various sources. 028 029 @author Ceki Gülcü 030 */ 031 032public class Loader { 033 034 static final String TSTR = "Caught Exception while in Loader.getResource. This may be innocuous."; 035 036 // We conservatively assume that we are running under Java 1.x 037 static private boolean java1 = true; 038 039 static private boolean ignoreTCL = false; 040 041 static { 042 String prop = OptionConverter.getSystemProperty("java.version", null); 043 044 if(prop != null) { 045 int i = prop.indexOf('.'); 046 if(i != -1) { 047 if(prop.charAt(i+1) != '1') 048 java1 = false; 049 } 050 } 051 String ignoreTCLProp = OptionConverter.getSystemProperty("log4j.ignoreTCL", null); 052 if(ignoreTCLProp != null) { 053 ignoreTCL = OptionConverter.toBoolean(ignoreTCLProp, true); 054 } 055 } 056 057 /** 058 * Get a resource by delegating to getResource(String). 059 * @param resource resource name 060 * @param clazz class, ignored. 061 * @return URL to resource or null. 062 * @deprecated as of 1.2. 063 */ 064 public static URL getResource(String resource, Class clazz) { 065 return getResource(resource); 066 } 067 068 /** 069 This method will search for <code>resource</code> in different 070 places. The search order is as follows: 071 072 <ol> 073 074 <p><li>Search for <code>resource</code> using the thread context 075 class loader under Java2. If that fails, search for 076 <code>resource</code> using the class loader that loaded this 077 class (<code>Loader</code>). Under JDK 1.1, only the the class 078 loader that loaded this class (<code>Loader</code>) is used. 079 080 <p><li>Try one last time with 081 <code>ClassLoader.getSystemResource(resource)</code>, that is is 082 using the system class loader in JDK 1.2 and virtual machine's 083 built-in class loader in JDK 1.1. 084 085 </ol> 086 */ 087 static public URL getResource(String resource) { 088 ClassLoader classLoader = null; 089 URL url = null; 090 091 try { 092 if(!java1 && !ignoreTCL) { 093 classLoader = getTCL(); 094 if(classLoader != null) { 095 LogLog.debug("Trying to find ["+resource+"] using context classloader " 096 +classLoader+"."); 097 url = classLoader.getResource(resource); 098 if(url != null) { 099 return url; 100 } 101 } 102 } 103 104 // We could not find resource. Ler us now try with the 105 // classloader that loaded this class. 106 classLoader = Loader.class.getClassLoader(); 107 if(classLoader != null) { 108 LogLog.debug("Trying to find ["+resource+"] using "+classLoader 109 +" class loader."); 110 url = classLoader.getResource(resource); 111 if(url != null) { 112 return url; 113 } 114 } 115 } catch(IllegalAccessException t) { 116 LogLog.warn(TSTR, t); 117 } catch(InvocationTargetException t) { 118 if (t.getTargetException() instanceof InterruptedException 119 || t.getTargetException() instanceof InterruptedIOException) { 120 Thread.currentThread().interrupt(); 121 } 122 LogLog.warn(TSTR, t); 123 } catch(Throwable t) { 124 // 125 // can't be InterruptedException or InterruptedIOException 126 // since not declared, must be error or RuntimeError. 127 LogLog.warn(TSTR, t); 128 } 129 130 // Last ditch attempt: get the resource from the class path. It 131 // may be the case that clazz was loaded by the Extentsion class 132 // loader which the parent of the system class loader. Hence the 133 // code below. 134 LogLog.debug("Trying to find ["+resource+ 135 "] using ClassLoader.getSystemResource()."); 136 return ClassLoader.getSystemResource(resource); 137 } 138 139 /** 140 Are we running under JDK 1.x? 141 */ 142 public 143 static 144 boolean isJava1() { 145 return java1; 146 } 147 148 /** 149 * Get the Thread Context Loader which is a JDK 1.2 feature. If we 150 * are running under JDK 1.1 or anything else goes wrong the method 151 * returns <code>null<code>. 152 * 153 * */ 154 private static ClassLoader getTCL() throws IllegalAccessException, 155 InvocationTargetException { 156 157 // Are we running on a JDK 1.2 or later system? 158 Method method = null; 159 try { 160 method = Thread.class.getMethod("getContextClassLoader", null); 161 } catch (NoSuchMethodException e) { 162 // We are running on JDK 1.1 163 return null; 164 } 165 166 return (ClassLoader) method.invoke(Thread.currentThread(), null); 167 } 168 169 170 171 /** 172 * If running under JDK 1.2 load the specified class using the 173 * <code>Thread</code> <code>contextClassLoader</code> if that 174 * fails try Class.forname. Under JDK 1.1 only Class.forName is 175 * used. 176 * 177 */ 178 static public Class loadClass (String clazz) throws ClassNotFoundException { 179 // Just call Class.forName(clazz) if we are running under JDK 1.1 180 // or if we are instructed to ignore the TCL. 181 if(java1 || ignoreTCL) { 182 return Class.forName(clazz); 183 } else { 184 try { 185 return getTCL().loadClass(clazz); 186 } 187 // we reached here because tcl was null or because of a 188 // security exception, or because clazz could not be loaded... 189 // In any case we now try one more time 190 catch(InvocationTargetException e) { 191 if (e.getTargetException() instanceof InterruptedException 192 || e.getTargetException() instanceof InterruptedIOException) { 193 Thread.currentThread().interrupt(); 194 } 195 } catch(Throwable t) { 196 } 197 } 198 return Class.forName(clazz); 199 } 200}