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/*
* Copyright 2005-2006 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.
*/
/* $Id$ */
package org.apache.fop.render;
import java.util.Iterator;
import java.util.List;
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 XMLHandlerRegistry {
/** the logger */
private static Log log = LogFactory.getLog(XMLHandlerRegistry.class);
/** Map containing XML handlers for various document types */
private Map handlers = new java.util.HashMap();
/**
* Default constructor.
*/
public XMLHandlerRegistry() {
discoverXMLHandlers();
}
/**
* Add a default XML handler which is able to handle any namespace.
* @param handler XMLHandler to use
*/
private void setDefaultXMLHandler(XMLHandler handler) {
addXMLHandler(XMLHandler.HANDLE_ALL, handler);
}
/**
* Add an XML handler. The handler itself is inspected to find out what it supports.
* @param classname the fully qualified class name
*/
public void addXMLHandler(String classname) {
try {
XMLHandler handlerInstance = (XMLHandler)Class.forName(classname).newInstance();
addXMLHandler(handlerInstance);
} 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 "
+ XMLHandler.class.getName());
}
}
/**
* Add an XML handler. The handler itself is inspected to find out what it supports.
* @param handler the XMLHandler instance
*/
public void addXMLHandler(XMLHandler handler) {
String ns = handler.getNamespace();
if (ns == null) {
setDefaultXMLHandler(handler);
} else {
addXMLHandler(ns, handler);
}
}
/**
* Add an XML handler for the given MIME type and XML namespace.
* @param ns Namespace URI
* @param handler XMLHandler to use
*/
private void addXMLHandler(String ns,
XMLHandler handler) {
List lst = (List)handlers.get(ns);
if (lst == null) {
lst = new java.util.ArrayList();
handlers.put(ns, lst);
}
lst.add(handler);
}
/**
* Returns an XMLHandler which handles an XML dialect of the given namespace and for
* a specified output format defined by its MIME type.
* @param renderer the Renderer for which to retrieve a Renderer
* @param ns the XML namespace associated with the XML to be rendered
* @return the XMLHandler responsible for handling the XML or null if none is available
*/
public XMLHandler getXMLHandler(Renderer renderer, String ns) {
XMLHandler handler;
List lst = (List)handlers.get(ns);
handler = getXMLHandler(renderer, lst);
if (handler == null) {
lst = (List)handlers.get(XMLHandler.HANDLE_ALL);
handler = getXMLHandler(renderer, lst);
}
return handler;
}
private XMLHandler getXMLHandler(Renderer renderer, List lst) {
XMLHandler handler;
if (lst != null) {
for (int i = 0, c = lst.size(); i < c; i++) {
//TODO Maybe add priorities later
handler = (XMLHandler)lst.get(i);
if (handler.supportsRenderer(renderer)) {
return handler;
}
}
}
return null; //No handler found
}
/**
* Discovers XMLHandler implementations through the classpath and dynamically
* registers them.
*/
private void discoverXMLHandlers() {
// add mappings from available services
Iterator providers = Service.providers(XMLHandler.class);
if (providers != null) {
while (providers.hasNext()) {
XMLHandler handler = (XMLHandler)providers.next();
try {
if (log.isDebugEnabled()) {
log.debug("Dynamically adding XMLHandler: " + handler.getClass().getName());
}
addXMLHandler(handler);
} catch (IllegalArgumentException e) {
log.error("Error while adding XMLHandler", e);
}
}
}
}
}
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