org.pageseeder.ox.OXEntityResolver Maven / Gradle / Ivy
/*
* Copyright 2021 Allette Systems (Australia)
* http://www.allette.com.au
*
* 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.pageseeder.ox;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import java.io.InputStream;
/**
* Resolves the identifiers specific to the OX itself.
*
* OX public identifiers should match the following:
*
*
* -//PageSeeder//DTD::OX model 1.0//EN
*
*
* Note: this resolver also accepts the alias prefix -//OX//DTD::.
*
* @author Christophe Lauret
* @author Ciber Cai
*
* @since OX 0.6.1
*/
public final class OXEntityResolver implements EntityResolver {
/**
* The prefix used by OX for all public identifiers.
*
* Public identifiers starting with any other prefix will be ignored.
*/
public static final String PUBLIC_ID_PREFIX = "-//PageSeeder//DTD::OX ";
/**
* The prefix used by OX for all public identifiers.
*
* Public identifiers starting with any other prefix will be ignored.
*/
private static final String ALIAS_ID_PREFIX = "-//OX//DTD::";
/**
* The suffix used by OX for all public identifiers.
*/
private static final String PUBLIC_ID_SUFFIX = "//EN";
/**
* A single instance.
*/
private static final OXEntityResolver SINGLETON = new OXEntityResolver();
/**
* A logger for this class.
*/
private static final Logger LOGGER = LoggerFactory.getLogger(OXEntityResolver.class);
/**
* Creates a new OX Entity resolver.
*/
private OXEntityResolver() {}
/**
* @see org.xml.sax.EntityResolver#resolveEntity(String, String)
*
* @param publicId The public identifier for the entity.
* @param systemId The system identifier for the entity.
*
* @return The entity as an XML input source.
*
* @throws SAXException If the library has not been defined.
*/
@Override
public InputSource resolveEntity(String publicId, String systemId) throws SAXException {
InputSource source = null;
// process only public identifiers that are valid for OX
String dtd = toFileName(publicId);
if (dtd != null) {
LOGGER.debug("resolved {} to /library/{}", publicId, dtd);
// return a special input source
InputStream inputStream = OXEntityResolver.class.getResourceAsStream("/library/" + dtd);
source = new InputSource(inputStream);
// use the default behaviour
} else {
LOGGER.info("Tried to use the entity resolver on unknown public ID '{}'", publicId);
}
return source;
}
/**
* Returns an entity resolver instance.
*
* @return an entity resolver instance.
*/
public static OXEntityResolver getInstance() {
return SINGLETON;
}
/**
* Returns the file name for the specified public ID.
*
* @param publicId the public identifier.
* @return The corresponding filename.
*/
private static String toFileName(String publicId) {
if (publicId == null) { return null; }
if (!publicId.endsWith(PUBLIC_ID_SUFFIX)) { return null; }
int length = publicId.length() - PUBLIC_ID_SUFFIX.length();
if (publicId.startsWith(PUBLIC_ID_PREFIX)) {
return publicId.substring(PUBLIC_ID_PREFIX.length(), length).toLowerCase().replace(' ', '-') + ".dtd";
} else if (publicId.startsWith(ALIAS_ID_PREFIX)) {
return publicId.substring(ALIAS_ID_PREFIX.length(), length).toLowerCase().replace(' ', '-') + ".dtd";
} else {
return null;
}
}
}