/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed 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.cocoon.components.elementprocessor.impl;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
import org.apache.avalon.framework.component.Component;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.cocoon.components.elementprocessor.CannotCreateElementProcessorException;
import org.apache.cocoon.components.elementprocessor.ElementProcessor;
import org.apache.cocoon.components.elementprocessor.ElementProcessorFactory;
/**
* Create instances of specific ElementProcessor implementations to
* handle specific XML elements and their content.
*
* @author Marc Johnson (marc_johnson27591@hotmail.com)
* @version CVS $Id: AbstractElementProcessorFactory.java,v 1.4 2004/03/05 13:02:03 bdelacretaz Exp $
*/
public abstract class AbstractElementProcessorFactory
extends AbstractLogEnabled implements ElementProcessorFactory, Component
{
// uses XML element names as keys and ElementProcessor progenitors
// as values. An ElementProcessor progenitor is an Object that can
// be used to create a new ElementProcessor instance that is
// specific to a particular XML element. A progenitor may be a
// Constructor or Class that can construct a new instance of an
// appropriate ElementProcessor implementation, or any other
// Object that an extension of AbstractElementProcessorFactory finds
// useful to create new ElementProcessor instances.
private Map _element_processor_map;
/**
* Protected default constructor
*/
protected AbstractElementProcessorFactory() {
_element_processor_map = new HashMap();
}
/**
* Given an XML element name, create and return an appropriate
* ElementProcessor.
*
* @param name element name
*
* @return the specified ElementProcessor
*
* @exception CannotCreateElementProcessorException if there is no
* ElementProcessor available for the specified name
*/
public ElementProcessor createElementProcessor(final String name)
throws CannotCreateElementProcessorException {
Object progenitor = lookupElementProcessorProgenitor(name);
if (progenitor == null) {
CannotCreateElementProcessorException exception =
new CannotCreateElementProcessorException(
"Cannot find progenitor for that name");
exception.setElementName(name);
throw exception;
}
ElementProcessor processor = null;
try {
processor = doCreateElementProcessor(progenitor);
} catch (CannotCreateElementProcessorException e) {
e.setElementName(name);
throw e;
}
return processor;
}
/**
* A method for extending classes to populate the map.
*
* @param name the element name for this progenitor; cannot be
* null ot empty
* @param progenitor an object that can be used to generate an
* appropriate ElementProcessor; cannot be nukk
*
* @exception IllegalArgumentException if name is already in the
* map or progenitor is null.
*/
protected void addElementProcessorProgenitor(final String name,
final Object progenitor)
{
if ((name == null) || (name.equals(""))) {
throw new IllegalArgumentException(
"Cannot use null or empty name as a key");
}
if (progenitor == null) {
throw new IllegalArgumentException(
"Cannot add null progenitor to the map");
}
if (_element_processor_map.put(name, progenitor) != null) {
throw new IllegalArgumentException(
name + " is already in use in the map");
}
}
/**
* A method to get the progenitor value associated with a
* specified element name.
*
* @param name the element name
*
* @return the associated ElementProcessor progenitor; will be
* null if the element name has not yet been associated
* with a progenitor.
*/
protected Object lookupElementProcessorProgenitor(final String name)
{
Object obj = _element_processor_map.get(name);
if (obj == null && !name.equals("*")) {
obj = lookupElementProcessorProgenitor("*");
}
return obj;
}
/**
* The method that a concrete extension of AbstractElementProcessorFactory
* must implement. When this method is called, the element name
* has already been looked up in the map and a progenitor Object
* has been acquired. The progenitor is guaranteed not to be null.
*
* @param progenitor the object from which to create an
* ElementProcessor
*
* @return freshly created ElementProcessor
*
* @exception CannotCreateElementProcessorException if the
* specified ElementProcessor cannot be created.
*/
protected abstract ElementProcessor doCreateElementProcessor(
final Object progenitor) throws CannotCreateElementProcessorException;
/**
* A reference implementation of doCreateElementProcessor that can
* be used by an extending class whose progenitors are Class
* objects for ElementProcessor implementations.
*
* @param progenitor a Class representing an ElementProcessor
*
* @return the new ElementProcessor instance
*
* @exception CannotCreateElementProcessorException if the
* ElementProcessor cannot be created.
*/
protected ElementProcessor createNewElementProcessorInstance(
final Class progenitor)
throws CannotCreateElementProcessorException {
ElementProcessor rval = null;
try {
rval = (ElementProcessor)progenitor.newInstance();
if (rval instanceof AbstractLogEnabled) {
((AbstractLogEnabled)rval).enableLogging(getLogger());
}
} catch (ExceptionInInitializerError e) {
throw new CannotCreateElementProcessorException(
"an exception (" + e + ") occurred in initializing the associated ElementProcessor class");
} catch (SecurityException e) {
throw new CannotCreateElementProcessorException(
"a security exception was caught while creating the associated ElementProcessor");
} catch (InstantiationException e) {
throw new CannotCreateElementProcessorException(
"associated ElementProcessor is an interface or abstract class or has no zero-parameter constructor");
} catch (IllegalAccessException e) {
throw new CannotCreateElementProcessorException(
"cannot access ElementProcessor class or its zero-parameter constructor");
} catch (ClassCastException e) {
throw new CannotCreateElementProcessorException(
"object created does not implement ElementProcessor");
} catch (Exception e) {
throw new CannotCreateElementProcessorException(
"exception (" + e
+ ") occured while creating new instance of ElementProcessor");
}
if (rval == null) {
throw new CannotCreateElementProcessorException(
"somehow generated a null ElementProcessor");
}
return rval;
}
/**
* A reference implementation of doCreateElementProcessor that can
* be used by an extending class whose progenitors are Constructor
* objects that can create new instances of ElementProcessor
* implementations.
*
* @param progenitor a Constructor of an ElementProcessor
*
* @return the newly created ElementProcessor
*
* @exception CannotCreateElementProcessorException if the
* ElementProcessor cannot be created.
*/
protected ElementProcessor constructElementProcessor(
final Constructor progenitor)
throws CannotCreateElementProcessorException {
ElementProcessor rval = null;
try {
rval = (ElementProcessor) progenitor.newInstance(new Object[0]);
if (rval instanceof AbstractLogEnabled) {
((AbstractLogEnabled)rval).enableLogging(getLogger());
}
} catch (ExceptionInInitializerError e) {
throw new CannotCreateElementProcessorException(
"an exception (" + e
+ ")occurred in initializing the associated ElementProcessor class");
} catch (IllegalArgumentException e) {
throw new CannotCreateElementProcessorException(
"the ElementProcessor constructor apparently needs parameters");
} catch (InstantiationException e) {
throw new CannotCreateElementProcessorException(
"associated ElementProcessor is an interface or abstract class");
} catch (IllegalAccessException e) {
throw new CannotCreateElementProcessorException(
"cannot access ElementProcessor class or its zero-parameter constructor");
} catch (InvocationTargetException e) {
throw new CannotCreateElementProcessorException(
"ElementProcessor constructor threw an exception ["
+ e.toString() + "]");
} catch (ClassCastException e) {
throw new CannotCreateElementProcessorException(
"object created does not implement ElementProcessor");
}
if (rval == null) {
throw new CannotCreateElementProcessorException(
"somehow generated a null ElementProcessor");
}
return rval;
}
} // end public abstract class AbstractElementProcessorFactory