org.apache.xmlgraphics.util.uri.CommonURIResolver 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.
*/
/* $Id: CommonURIResolver.java 1804124 2017-08-04 14:13:54Z ssteiner $ */
package org.apache.xmlgraphics.util.uri;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import javax.xml.transform.Source;
import javax.xml.transform.TransformerException;
import javax.xml.transform.URIResolver;
import org.apache.xmlgraphics.util.Service;
/**
* A URI Resolver which supports pluggable entities via the {@link Service}
* mechanism.
*
* This resolver will try all resolvers registered as an {@link URIResolver}
* class. For proper operation, the registers URIResolvers must return null if
* they cannot handle the given URI and fail fast.
*/
public class CommonURIResolver implements URIResolver {
private final List uriResolvers = new LinkedList();
private static final class DefaultInstanceHolder {
private static final CommonURIResolver INSTANCE = new CommonURIResolver();
}
/**
* Creates a new CommonURIResolver. Use this if you need support for
* resolvers in the current context.
* @see CommonURIResolver#getDefaultURIResolver()
*/
public CommonURIResolver() {
Iterator iter = Service.providers(URIResolver.class);
while (iter.hasNext()) {
URIResolver resolver = (URIResolver) iter.next();
register(resolver);
}
}
/**
* Retrieve the default resolver instance.
*
* @return the default resolver instance.
*/
public static CommonURIResolver getDefaultURIResolver() {
return DefaultInstanceHolder.INSTANCE;
}
/** {@inheritDoc} */
public Source resolve(String href, String base) {
synchronized (uriResolvers) {
for (Object uriResolver : uriResolvers) {
final URIResolver currentResolver = (URIResolver) uriResolver;
try {
final Source result = currentResolver.resolve(href, base);
if (result != null) {
return result;
}
} catch (TransformerException e) {
// Ignore.
}
}
}
return null;
}
/**
* Register a given {@link URIResolver} while the software is running.
*
* @param uriResolver
* the resolver to register.
*/
public void register(URIResolver uriResolver) {
synchronized (uriResolvers) {
uriResolvers.add(uriResolver);
}
}
/**
* Unregister a given {@link URIResolver} while the software is running.
*
* @param uriResolver
* the resolver to unregister.
*/
public void unregister(URIResolver uriResolver) {
synchronized (uriResolvers) {
uriResolvers.remove(uriResolver);
}
}
}