/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software
* License version 1.1, a copy of which has been included with this
* distribution in the LICENSE.txt file. */
package org.apache.log4j.helpers;
import java.net.URL;
import java.lang.IllegalAccessException;
import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;
//import java.awt.Image;
//import java.awt.Toolkit;
/**
Load resources (or images) from various sources.
@author Ceki Gülcü
*/
public class Loader {
static final String TSTR = "Caught Exception while in Loader.getResource. This may be innocuous.";
// We conservatively assume that we are running under Java 1.x
static private boolean java1 = true;
static private boolean ignoreTCL = false;
static {
String prop = OptionConverter.getSystemProperty("java.version", null);
if(prop != null) {
int i = prop.indexOf('.');
if(i != -1) {
if(prop.charAt(i+1) != '1')
java1 = false;
}
}
String ignoreTCLProp = OptionConverter.getSystemProperty("log4j.ignoreTCL", null);
if(ignoreTCLProp != null) {
ignoreTCL = OptionConverter.toBoolean(ignoreTCLProp, true);
}
}
/**
This method will search for <code>resource</code> in different
places. The rearch order is as follows:
<ol>
<p><li>Search for <code>resource</code> using the thread context
class loader under Java2. If that fails, search for
<code>resource</code> using the class loader that loaded this
class (<code>Loader</code>). Under JDK 1.1, only the the class
loader that loaded this class (<code>Loader</code>) is used.
<p><li>Try one last time with
<code>ClassLoader.getSystemResource(resource)</code>, that is is
using the system class loader in JDK 1.2 and virtual machine's
built-in class loader in JDK 1.1.
</ol>
*/
static public URL getResource(String resource) {
ClassLoader classLoader = null;
URL url = null;
try {
if(!java1) {
classLoader = getTCL();
if(classLoader != null) {
LogLog.debug("Trying to find ["+resource+"] using context classloader "
+classLoader+".");
url = classLoader.getResource(resource);
if(url != null) {
return url;
}
}
}
// We could not find resource. Ler us now try with the
// classloader that loaded this class.
classLoader = Loader.class.getClassLoader();
if(classLoader != null) {
LogLog.debug("Trying to find ["+resource+"] using "+classLoader
+" class loader.");
url = classLoader.getResource(resource);
if(url != null) {
return url;
}
}
} catch(Throwable t) {
LogLog.warn(TSTR, t);
}
// Last ditch attempt: get the resource from the class path. It
// may be the case that clazz was loaded by the Extentsion class
// loader which the parent of the system class loader. Hence the
// code below.
LogLog.debug("Trying to find ["+resource+
"] using ClassLoader.getSystemResource().");
return ClassLoader.getSystemResource(resource);
}
/**
Are we running under JDK 1.x?
*/
public
static
boolean isJava1() {
return java1;
}
/**
* Get the Thread Context Loader which is a JDK 1.2 feature. If we
* are running under JDK 1.1 or anything else goes wrong the method
* returns <code>null<code>.
*
* */
private static ClassLoader getTCL() throws IllegalAccessException,
InvocationTargetException {
// Are we running on a JDK 1.2 or later system?
Method method = null;
try {
method = Thread.class.getMethod("getContextClassLoader", null);
} catch (NoSuchMethodException e) {
// We are running on JDK 1.1
return null;
}
return (ClassLoader) method.invoke(Thread.currentThread(), null);
}
/**
* If running under JDK 1.2 load the specified class using the
* <code>Thread</code> <code>contextClassLoader</code> if that
* fails try Class.forname. Under JDK 1.1 only Class.forName is
* used.
*
*/
static public Class loadClass (String clazz) throws ClassNotFoundException {
// Just call Class.forName(clazz) if we are running under JDK 1.1
// or if we are instructed to ignore the TCL.
if(java1 || ignoreTCL) {
return Class.forName(clazz);
} else {
try {
return getTCL().loadClass(clazz);
} catch(Throwable e) {
// we reached here because tcl was null or because of a
// security exception, or because clazz could not be loaded...
// In any case we now try one more time
return Class.forName(clazz);
}
}
}
}
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