001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.beans.factory.xml;
018
019import java.io.File;
020import java.io.IOException;
021import java.net.URL;
022import java.net.URLDecoder;
023
024import org.apache.commons.logging.Log;
025import org.apache.commons.logging.LogFactory;
026import org.xml.sax.InputSource;
027import org.xml.sax.SAXException;
028
029import org.springframework.core.io.Resource;
030import org.springframework.core.io.ResourceLoader;
031
032/**
033 * {@code EntityResolver} implementation that tries to resolve entity references
034 * through a {@link org.springframework.core.io.ResourceLoader} (usually,
035 * relative to the resource base of an {@code ApplicationContext}), if applicable.
036 * Extends {@link DelegatingEntityResolver} to also provide DTD and XSD lookup.
037 *
038 * <p>Allows to use standard XML entities to include XML snippets into an
039 * application context definition, for example to split a large XML file
040 * into various modules. The include paths can be relative to the
041 * application context's resource base as usual, instead of relative
042 * to the JVM working directory (the XML parser's default).
043 *
044 * <p>Note: In addition to relative paths, every URL that specifies a
045 * file in the current system root, i.e. the JVM working directory,
046 * will be interpreted relative to the application context too.
047 *
048 * @author Juergen Hoeller
049 * @since 31.07.2003
050 * @see org.springframework.core.io.ResourceLoader
051 * @see org.springframework.context.ApplicationContext
052 */
053public class ResourceEntityResolver extends DelegatingEntityResolver {
054
055        private static final Log logger = LogFactory.getLog(ResourceEntityResolver.class);
056
057        private final ResourceLoader resourceLoader;
058
059
060        /**
061         * Create a ResourceEntityResolver for the specified ResourceLoader
062         * (usually, an ApplicationContext).
063         * @param resourceLoader the ResourceLoader (or ApplicationContext)
064         * to load XML entity includes with
065         */
066        public ResourceEntityResolver(ResourceLoader resourceLoader) {
067                super(resourceLoader.getClassLoader());
068                this.resourceLoader = resourceLoader;
069        }
070
071
072        @Override
073        public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
074                InputSource source = super.resolveEntity(publicId, systemId);
075
076                if (source == null && systemId != null) {
077                        String resourcePath = null;
078                        try {
079                                String decodedSystemId = URLDecoder.decode(systemId, "UTF-8");
080                                String givenUrl = new URL(decodedSystemId).toString();
081                                String systemRootUrl = new File("").toURI().toURL().toString();
082                                // Try relative to resource base if currently in system root.
083                                if (givenUrl.startsWith(systemRootUrl)) {
084                                        resourcePath = givenUrl.substring(systemRootUrl.length());
085                                }
086                        }
087                        catch (Exception ex) {
088                                // Typically a MalformedURLException or AccessControlException.
089                                if (logger.isDebugEnabled()) {
090                                        logger.debug("Could not resolve XML entity [" + systemId + "] against system root URL", ex);
091                                }
092                                // No URL (or no resolvable URL) -> try relative to resource base.
093                                resourcePath = systemId;
094                        }
095                        if (resourcePath != null) {
096                                if (logger.isTraceEnabled()) {
097                                        logger.trace("Trying to locate XML entity [" + systemId + "] as resource [" + resourcePath + "]");
098                                }
099                                Resource resource = this.resourceLoader.getResource(resourcePath);
100                                source = new InputSource(resource.getInputStream());
101                                source.setPublicId(publicId);
102                                source.setSystemId(systemId);
103                                if (logger.isDebugEnabled()) {
104                                        logger.debug("Found XML entity [" + systemId + "]: " + resource);
105                                }
106                        }
107                        else if (systemId.endsWith(DTD_SUFFIX) || systemId.endsWith(XSD_SUFFIX)) {
108                                // External dtd/xsd lookup via https even for canonical http declaration
109                                String url = systemId;
110                                if (url.startsWith("http:")) {
111                                        url = "https:" + url.substring(5);
112                                }
113                                try {
114                                        source = new InputSource(new URL(url).openStream());
115                                        source.setPublicId(publicId);
116                                        source.setSystemId(systemId);
117                                }
118                                catch (IOException ex) {
119                                        if (logger.isDebugEnabled()) {
120                                                logger.debug("Could not resolve XML entity [" + systemId + "] through URL [" + url + "]", ex);
121                                        }
122                                        // Fall back to the parser's default behavior.
123                                        source = null;
124                                }
125                        }
126                }
127
128                return source;
129        }
130
131}