001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.configuration2.resolver; 018 019import java.io.IOException; 020import java.io.InputStream; 021import java.net.URL; 022import java.net.URLConnection; 023import java.util.HashMap; 024import java.util.Map; 025 026import org.xml.sax.EntityResolver; 027import org.xml.sax.InputSource; 028import org.xml.sax.SAXException; 029 030/** 031 * The DefaultEntityResolver used by XML Configurations. 032 * 033 * @since 1.7 034 */ 035public class DefaultEntityResolver implements EntityResolver, EntityRegistry { 036 /** Stores a map with the registered public IDs. */ 037 private final Map<String, URL> registeredEntities = new HashMap<>(); 038 039 /** 040 * <p> 041 * Registers the specified URL for the specified public identifier. 042 * </p> 043 * <p> 044 * This implementation maps {@code PUBLICID}'s to URLs (from which the resource will be loaded). A common use case for 045 * this method is to register local URLs (possibly computed at runtime by a class loader) for DTDs and Schemas. This 046 * allows the performance advantage of using a local version without having to ensure every {@code SYSTEM} URI on every 047 * processed XML document is local. This implementation provides only basic functionality. If more sophisticated 048 * features are required, either calling {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom 049 * {@code DocumentBuilder} (which also can be initialized with a custom {@code EntityResolver}) or creating a custom 050 * entity resolver and registering it with the XMLConfiguration is recommended. 051 * </p> 052 * 053 * @param publicId Public identifier of the Entity to be resolved 054 * @param entityURL The URL to use for reading this Entity 055 * @throws IllegalArgumentException if the public ID is undefined 056 */ 057 @Override 058 public void registerEntityId(final String publicId, final URL entityURL) { 059 if (publicId == null) { 060 throw new IllegalArgumentException("Public ID must not be null!"); 061 } 062 getRegisteredEntities().put(publicId, entityURL); 063 } 064 065 /** 066 * Resolves the requested external entity. This is the default implementation of the {@code EntityResolver} interface. 067 * It checks the passed in public ID against the registered entity IDs and uses a local URL if possible. 068 * 069 * @param publicId the public identifier of the entity being referenced 070 * @param systemId the system identifier of the entity being referenced 071 * @return an input source for the specified entity 072 * @throws org.xml.sax.SAXException if a parsing exception occurs 073 */ 074 @SuppressWarnings("resource") // The stream is managed by the InputSource returned by this method. 075 @Override 076 public InputSource resolveEntity(final String publicId, final String systemId) throws SAXException { 077 // Has this system identifier been registered? 078 URL entityURL = null; 079 if (publicId != null) { 080 entityURL = getRegisteredEntities().get(publicId); 081 } 082 083 if (entityURL != null) { 084 // Obtain an InputSource for this URL. This code is based on the 085 // createInputSourceFromURL() method of Commons Digester. 086 try { 087 final URLConnection connection = entityURL.openConnection(); 088 connection.setUseCaches(false); 089 final InputStream stream = connection.getInputStream(); 090 final InputSource source = new InputSource(stream); 091 source.setSystemId(entityURL.toExternalForm()); 092 return source; 093 } catch (final IOException e) { 094 throw new SAXException(e); 095 } 096 } 097 // default processing behavior 098 return null; 099 } 100 101 /** 102 * Gets a map with the entity IDs that have been registered using the {@code registerEntityId()} method. 103 * 104 * @return a map with the registered entity IDs 105 */ 106 @Override 107 public Map<String, URL> getRegisteredEntities() { 108 return registeredEntities; 109 } 110}