public static 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);
}

This method will search for resource in different places. The search order is as follows:

1. Search for resource using the thread context class loader under Java2. If that fails, search for resource using the class loader that loaded this class (Loader). Under JDK 1.1, only the the class loader that loaded this class (Loader) is used.

2. Try one last time with ClassLoader.getSystemResource(resource), that is is using the system class loader in JDK 1.2 and virtual machine's built-in class loader in JDK 1.1.

 public static URL getResource(String resource,
    Class clazz) 
{
  
    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);      
    }   
      return getResource(resource);
}

Get a resource by delegating to getResource(String).

 public static boolean isJava1() 
{
    return java1;
}

Are we running under JDK 1.x?

 public static 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);
      }
    }
}

If running under JDK 1.2 load the specified class using the Thread contextClassLoader if that fails try Class.forname. Under JDK 1.1 only Class.forName is used.