org.apache.log4j.or.RendererMap Maven / Gradle / Ivy
/*
* 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.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();
public
RendererMap() {
map = new Hashtable();
}
/**
Add a renderer to a hierarchy passed as parameter.
*/
static
public
void addRenderer(RendererSupport repository, String renderedClassName,
String renderingClassName) {
LogLog.debug("Rendering class: ["+renderingClassName+"], Rendered class: ["+
renderedClassName+"].");
ObjectRenderer renderer = (ObjectRenderer)
OptionConverter.instantiateByClassName(renderingClassName,
ObjectRenderer.class,
null);
if(renderer == null) {
LogLog.error("Could not instantiate renderer ["+renderingClassName+"].");
return;
} 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}. */
public
String findAndRender(Object o) {
if(o == null)
return null;
else
return get(o.getClass()).doRender(o);
}
/**
Syntactic sugar method that calls {@link #get(Class)} with the
class of the object parameter. */
public
ObjectRenderer get(Object o) {
if(o == null)
return null;
else
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 renderers Value 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);
}
}