org.pageseeder.flint.ixml.FlintEntityResolver Maven / Gradle / Ivy
/*
* Copyright 2015 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.flint.ixml;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
/**
* Resolves the public identifiers used by Flint.
*
* Flint public identifiers should match the following:
*
*
* -//Weborganic//DTD::Flint [name_of_schema]//EN
*
*
* @author Christophe Lauret (Weborganic)
*
* @version 1 March 2010
*/
public final class FlintEntityResolver implements EntityResolver {
/**
* The old prefix used by Flint for all public identifiers.
*/
public static final String PUBLIC_ID_PREFIX_LEGACY = "-//Weborganic//DTD::Flint Index Documents ";
/**
* The prefix used by Flint for all public identifiers.
*
* Public identifiers starting with any other prefix than this one or the legacy one will be ignored.
*/
public static final String PUBLIC_ID_PREFIX = "-//Flint//DTD::Index Documents ";
/**
* The suffix used by Flint for all public identifiers.
*/
private static final String PUBLIC_ID_SUFFIX = "//EN";
/**
* This class is a singleton.
*/
private static final FlintEntityResolver SINGLETON = new FlintEntityResolver();
/**
* Creates a new Flint Entity resolver - singleton: keep it private.
*/
private FlintEntityResolver() {
}
/**
* @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 {
// process only public identifiers that are valid for Flint
String dtd = toFileName(publicId);
if (dtd != null) {
// Try to find the resource based on the public ID first.
InputStream inputStream = FlintEntityResolver.class.getResourceAsStream("/library/"+dtd);
// Try the System ID if this fails.
if (inputStream == null) {
inputStream = toInputStream(systemId);
}
// Give up
if (inputStream == null)
return null;
return new InputSource(inputStream);
// use the default behaviour
} else return null;
}
/**
* Returns the file name for the specified public ID.
*
* Only "-//Weborganic//DTD::Flint"
*
* @param publicId the public identifier.
* @return The corresponding filename.
*/
private static String toFileName(String publicId) {
if (publicId == null) return null;
String version = null;
if (publicId.startsWith(PUBLIC_ID_PREFIX)) {
int length = publicId.endsWith(PUBLIC_ID_SUFFIX)? publicId.length() - PUBLIC_ID_SUFFIX.length() : publicId.length();
if (length <= PUBLIC_ID_PREFIX.length()) return null;
version = publicId.substring(PUBLIC_ID_PREFIX.length(), length);
} else if (publicId.startsWith(PUBLIC_ID_PREFIX_LEGACY)) {
int length = publicId.endsWith(PUBLIC_ID_PREFIX_LEGACY)? publicId.length() - PUBLIC_ID_PREFIX_LEGACY.length() : publicId.length();
if (length <= PUBLIC_ID_PREFIX_LEGACY.length()) return null;
version = publicId.substring(PUBLIC_ID_PREFIX_LEGACY.length(), length);
}
if (version == null) return null;
return "index-documents-" + version + ".dtd";
}
/**
* Returns the single instance defined in this class.
*
* @return The single instance defined in this class.
*/
public static FlintEntityResolver getInstance() {
return SINGLETON;
}
// Private helpers
// ----------------------------------------------------------------------------------------------
/**
* Returns the input stream for the specified system ID.
*
* @param systemId The system ID
* @return The corresponding resource or null;
* @throws SAXException Wrap any IO or malformed URL exception.
*/
private InputStream toInputStream(String systemId) throws SAXException {
// Try to use the system ID then
if (systemId.startsWith("http")) {
try {
URL url = new URL(systemId);
return url.openStream();
} catch (IOException ex) {
throw new SAXException("Unable to resolve entity.", ex);
}
} else {
try {
return new FileInputStream(systemId);
} catch (FileNotFoundException ex) {
throw new SAXException("Unable to resolve entity.", ex);
}
}
}
}