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18 package org.apache.log4j.helpers;
19
20 import java.net.URL;
21 import java.lang.IllegalAccessException;
22 import java.lang.reflect.Method;
23 import java.lang.reflect.InvocationTargetException;
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
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) {
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
105
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(Throwable t) {
116 LogLog.warn(TSTR, t);
117 }
118
119
120
121
122
123 LogLog.debug("Trying to find ["+resource+
124 "] using ClassLoader.getSystemResource().");
125 return ClassLoader.getSystemResource(resource);
126 }
127
128 /***
129 Are we running under JDK 1.x?
130 */
131 public
132 static
133 boolean isJava1() {
134 return java1;
135 }
136
137 /***
138 * Get the Thread Context Loader which is a JDK 1.2 feature. If we
139 * are running under JDK 1.1 or anything else goes wrong the method
140 * returns <code>null<code>.
141 *
142 * */
143 private static ClassLoader getTCL() throws IllegalAccessException,
144 InvocationTargetException {
145
146
147 Method method = null;
148 try {
149 method = Thread.class.getMethod("getContextClassLoader", null);
150 } catch (NoSuchMethodException e) {
151
152 return null;
153 }
154
155 return (ClassLoader) method.invoke(Thread.currentThread(), null);
156 }
157
158
159
160 /***
161 * If running under JDK 1.2 load the specified class using the
162 * <code>Thread</code> <code>contextClassLoader</code> if that
163 * fails try Class.forname. Under JDK 1.1 only Class.forName is
164 * used.
165 *
166 */
167 static public Class loadClass (String clazz) throws ClassNotFoundException {
168
169
170 if(java1 || ignoreTCL) {
171 return Class.forName(clazz);
172 } else {
173 try {
174 return getTCL().loadClass(clazz);
175 } catch(Throwable e) {
176
177
178
179 return Class.forName(clazz);
180 }
181 }
182 }
183 }