1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.log4j.helpers;
19
20 import java.net.URL;
21 import java.lang.reflect.Method;
22 import java.lang.reflect.InvocationTargetException;
23 import java.io.InterruptedIOException;
24
25
26 /**
27 Load resources (or images) from various sources.
28
29 @author Ceki Gülcü
30 */
31
32 public class Loader {
33
34 static final String TSTR = "Caught Exception while in Loader.getResource. This may be innocuous.";
35
36 // We conservatively assume that we are running under Java 1.x
37 static private boolean java1 = true;
38
39 static private boolean ignoreTCL = false;
40
41 static {
42 String prop = OptionConverter.getSystemProperty("java.version", null);
43
44 if(prop != null) {
45 int i = prop.indexOf('.');
46 if(i != -1) {
47 if(prop.charAt(i+1) != '1')
48 java1 = false;
49 }
50 }
51 String ignoreTCLProp = OptionConverter.getSystemProperty("log4j.ignoreTCL", null);
52 if(ignoreTCLProp != null) {
53 ignoreTCL = OptionConverter.toBoolean(ignoreTCLProp, true);
54 }
55 }
56
57 /**
58 * Get a resource by delegating to getResource(String).
59 * @param resource resource name
60 * @param clazz class, ignored.
61 * @return URL to resource or null.
62 * @deprecated as of 1.2.
63 */
64 public static URL getResource(String resource, Class clazz) {
65 return getResource(resource);
66 }
67
68 /**
69 This method will search for <code>resource</code> in different
70 places. The search order is as follows:
71
72 <ol>
73
74 <p><li>Search for <code>resource</code> using the thread context
75 class loader under Java2. If that fails, search for
76 <code>resource</code> using the class loader that loaded this
77 class (<code>Loader</code>). Under JDK 1.1, only the the class
78 loader that loaded this class (<code>Loader</code>) is used.
79
80 <p><li>Try one last time with
81 <code>ClassLoader.getSystemResource(resource)</code>, that is is
82 using the system class loader in JDK 1.2 and virtual machine's
83 built-in class loader in JDK 1.1.
84
85 </ol>
86 */
87 static public URL getResource(String resource) {
88 ClassLoader classLoader = null;
89 URL url = null;
90
91 try {
92 if(!java1 && !ignoreTCL) {
93 classLoader = getTCL();
94 if(classLoader != null) {
95 LogLog.debug("Trying to find ["+resource+"] using context classloader "
96 +classLoader+".");
97 url = classLoader.getResource(resource);
98 if(url != null) {
99 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 }