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/*
* 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.
*/
/* $Id$ */
package org.apache.fop.util;
import java.util.Iterator;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.xmlgraphics.util.Service;
/**
* This class holds references to various XML handlers used by FOP. It also
* supports automatic discovery of additional XML handlers available through
* the class path.
*/
public class ContentHandlerFactoryRegistry {
/** the logger */
private static Log log = LogFactory.getLog(ContentHandlerFactoryRegistry.class);
/** Map from namespace URIs to ContentHandlerFactories */
private Map factories = new java.util.HashMap();
/**
* Default constructor.
*/
public ContentHandlerFactoryRegistry() {
discover();
}
/**
* Add an XML handler. The handler itself is inspected to find out what it supports.
* @param classname the fully qualified class name
*/
public void addContentHandlerFactory(String classname) {
try {
ContentHandlerFactory factory
= (ContentHandlerFactory)Class.forName(classname).newInstance();
addContentHandlerFactory(factory);
} catch (ClassNotFoundException e) {
throw new IllegalArgumentException("Could not find "
+ classname);
} catch (InstantiationException e) {
throw new IllegalArgumentException("Could not instantiate "
+ classname);
} catch (IllegalAccessException e) {
throw new IllegalArgumentException("Could not access "
+ classname);
} catch (ClassCastException e) {
throw new IllegalArgumentException(classname
+ " is not an "
+ ContentHandlerFactory.class.getName());
}
}
/**
* Add an ContentHandlerFactory. The instance is inspected to find out what it supports.
* @param factory the ContentHandlerFactory instance
*/
public void addContentHandlerFactory(ContentHandlerFactory factory) {
String[] ns = factory.getSupportedNamespaces();
for (int i = 0; i < ns.length; i++) {
factories.put(ns[i], factory);
}
}
/**
* Retrieves a ContentHandlerFactory instance of a given namespace URI.
* @param namespaceURI the namespace to be handled.
* @return the ContentHandlerFactory or null, if no suitable instance is available.
*/
public ContentHandlerFactory getFactory(String namespaceURI) {
ContentHandlerFactory factory = (ContentHandlerFactory)factories.get(namespaceURI);
return factory;
}
/**
* Discovers ContentHandlerFactory implementations through the classpath and dynamically
* registers them.
*/
private void discover() {
// add mappings from available services
Iterator providers = Service.providers(ContentHandlerFactory.class);
if (providers != null) {
while (providers.hasNext()) {
ContentHandlerFactory factory = (ContentHandlerFactory)providers.next();
try {
if (log.isDebugEnabled()) {
log.debug("Dynamically adding ContentHandlerFactory: "
+ factory.getClass().getName());
}
addContentHandlerFactory(factory);
} catch (IllegalArgumentException e) {
log.error("Error while adding ContentHandlerFactory", e);
}
}
}
}
}
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