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 * Copyright 2002-2019 the original author or authors.
 *
 * 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
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing, software
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package org.springframework.beans.factory.xml;

import java.io.FileNotFoundException;
import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;

EntityResolver implementation for the Spring beans DTD, to load the DTD from the Spring class path (or JAR file).

Fetches "spring-beans.dtd" from the class path resource "/org/springframework/beans/factory/xml/spring-beans.dtd", no matter whether specified as some local URL that includes "spring-beans" in the DTD name or as "https://www.springframework.org/dtd/spring-beans-2.0.dtd".

Author:Juergen Hoeller, Colin Sampaleanu
See Also:
Since:04.06.2003
/** * {@link EntityResolver} implementation for the Spring beans DTD, * to load the DTD from the Spring class path (or JAR file). * * <p>Fetches "spring-beans.dtd" from the class path resource * "/org/springframework/beans/factory/xml/spring-beans.dtd", * no matter whether specified as some local URL that includes "spring-beans" * in the DTD name or as "https://www.springframework.org/dtd/spring-beans-2.0.dtd". * * @author Juergen Hoeller * @author Colin Sampaleanu * @since 04.06.2003 * @see ResourceEntityResolver */
public class BeansDtdResolver implements EntityResolver { private static final String DTD_EXTENSION = ".dtd"; private static final String DTD_NAME = "spring-beans"; private static final Log logger = LogFactory.getLog(BeansDtdResolver.class); @Override @Nullable public InputSource resolveEntity(@Nullable String publicId, @Nullable String systemId) throws IOException { if (logger.isTraceEnabled()) { logger.trace("Trying to resolve XML entity with public ID [" + publicId + "] and system ID [" + systemId + "]"); } if (systemId != null && systemId.endsWith(DTD_EXTENSION)) { int lastPathSeparator = systemId.lastIndexOf('/'); int dtdNameStart = systemId.indexOf(DTD_NAME, lastPathSeparator); if (dtdNameStart != -1) { String dtdFile = DTD_NAME + DTD_EXTENSION; if (logger.isTraceEnabled()) { logger.trace("Trying to locate [" + dtdFile + "] in Spring jar on classpath"); } try { Resource resource = new ClassPathResource(dtdFile, getClass()); InputSource source = new InputSource(resource.getInputStream()); source.setPublicId(publicId); source.setSystemId(systemId); if (logger.isTraceEnabled()) { logger.trace("Found beans DTD [" + systemId + "] in classpath: " + dtdFile); } return source; } catch (FileNotFoundException ex) { if (logger.isDebugEnabled()) { logger.debug("Could not resolve beans DTD [" + systemId + "]: not found in classpath", ex); } } } } // Fall back to the parser's default behavior. return null; } @Override public String toString() { return "EntityResolver for spring-beans DTD"; } }