java/src/org/apache/log4j/helpers/Loader.java

@@ -0,0 +1,200 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.log4j.helpers;
+
+import java.net.URL;
+import java.lang.reflect.Method;
+import java.lang.reflect.InvocationTargetException;
+import java.io.InterruptedIOException;
+
+
+/**
+   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);      
+    }   
+  }
+  
+  /**
+   *  Get a resource by delegating to getResource(String).
+   *  @param resource resource name
+   *  @param clazz class, ignored.
+   *  @return URL to resource or null.
+   *  @deprecated as of 1.2.
+   */
+  public static URL getResource(String resource, Class clazz) {
+      return getResource(resource);
+  }
+
+  /**
+     This method will search for <code>resource</code> in different
+     places. The search 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 && !ignoreTCL) {
+  	  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(IllegalAccessException t) {
+        LogLog.warn(TSTR, t);
+    } catch(InvocationTargetException t) {
+        if (t.getTargetException() instanceof InterruptedException
+                || t.getTargetException() instanceof InterruptedIOException) {
+            Thread.currentThread().interrupt();
+        }
+        LogLog.warn(TSTR, t);
+    } catch(Throwable t) {
+      //
+      //  can't be InterruptedException or InterruptedIOException
+      //    since not declared, must be error or RuntimeError.
+      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);
+      }
+      // 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
+      catch(InvocationTargetException e) {
+          if (e.getTargetException() instanceof InterruptedException
+                  || e.getTargetException() instanceof InterruptedIOException) {
+              Thread.currentThread().interrupt();
+          }
+      } catch(Throwable t) {
+      }
+    }
+    return Class.forName(clazz);
+  }
+}