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What this is

This file is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

 * 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.or;

import org.apache.log4j.spi.RendererSupport;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.helpers.Loader;
import org.apache.log4j.helpers.OptionConverter;
import java.util.Hashtable;

   Map class objects to an {@link ObjectRenderer}.

   @author Ceki Gülcü
   @since version 1.0 */
public class RendererMap {

  Hashtable map;

  static ObjectRenderer defaultRenderer = new DefaultRenderer();

  RendererMap() {
    map = new Hashtable();

     Add a renderer to a hierarchy passed as parameter.
  void addRenderer(RendererSupport repository, String renderedClassName,
		   String renderingClassName) {
    LogLog.debug("Rendering class: ["+renderingClassName+"], Rendered class: ["+
    ObjectRenderer renderer = (ObjectRenderer)
    if(renderer == null) {
      LogLog.error("Could not instantiate renderer ["+renderingClassName+"].");
    } else {
      try {
	Class renderedClass = Loader.loadClass(renderedClassName);
	repository.setRenderer(renderedClass, renderer);
      } catch(ClassNotFoundException e) {
	LogLog.error("Could not find class ["+renderedClassName+"].", e);

     Find the appropriate renderer for the class type of the
     o parameter. This is accomplished by calling the
     {@link #get(Class)} method. Once a renderer is found, it is
     applied on the object o and the result is returned
     as a {@link String}. */
  String findAndRender(Object o) {
    if(o == null)
      return null;
      return get(o.getClass()).doRender(o);

     Syntactic sugar method that calls {@link #get(Class)} with the
     class of the object parameter. */
  ObjectRenderer get(Object o) {
    if(o == null)
      return null;
      return get(o.getClass());

     Search the parents of clazz for a renderer. The
     renderer closest in the hierarchy will be returned. If no
     renderers could be found, then the default renderer is returned.


The search first looks for a renderer configured for clazz. If a renderer could not be found, then the search continues by looking at all the interfaces implemented by clazz including the super-interfaces of each interface. If a renderer cannot be found, then the search looks for a renderer defined for the parent (superclass) of clazz. If that fails, then all the interfaces implemented by the parent of clazz are searched and so on.

For example, if A0, A1, A2 are classes and X0, X1, X2, Y0, Y1 are interfaces where A2 extends A1 which in turn extends A0 and similarly X2 extends X1 which extends X0 and Y1 extends Y0. Let us also assume that A1 implements the Y0 interface and that A2 implements the X2 interface.

The table below shows the results returned by the get(A2.class) method depending on the renderers added to the map.

Added renderersValue returned by get(A2.class)
A0Renderer A0Renderer
A0Renderer, A1Renderer A1Renderer
X0Renderer X0Renderer
A1Renderer, X0Renderer X0Renderer

This search algorithm is not the most natural, although it is particularly easy to implement. Future log4j versions may implement a more intuitive search algorithm. However, the present algorithm should be acceptable in the vast majority of circumstances. */ public ObjectRenderer get(Class clazz) { //System.out.println("\nget: "+clazz); ObjectRenderer r = null; for(Class c = clazz; c != null; c = c.getSuperclass()) { //System.out.println("Searching for class: "+c); r = (ObjectRenderer) map.get(c); if(r != null) { return r; } r = searchInterfaces(c); if(r != null) return r; } return defaultRenderer; } ObjectRenderer searchInterfaces(Class c) { //System.out.println("Searching interfaces of class: "+c); ObjectRenderer r = (ObjectRenderer) map.get(c); if(r != null) { return r; } else { Class[] ia = c.getInterfaces(); for(int i = 0; i < ia.length; i++) { r = searchInterfaces(ia[i]); if(r != null) return r; } } return null; } public ObjectRenderer getDefaultRenderer() { return defaultRenderer; } public void clear() { map.clear(); } /** Register an {@link ObjectRenderer} for clazz. */ public void put(Class clazz, ObjectRenderer or) { map.put(clazz, or); } }

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