spring xml EntityResolver

1 接口的声明

package org.xml.sax;

import java.io.IOException;
public interface EntityResolver {

  public abstract InputSource resolveEntity (String publicId,
					       String systemId)
	throws SAXException, IOException;
    
}

 2 spring 对xml的实体转化实现

package org.springframework.beans.factory.xml;

import java.io.IOException;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import org.springframework.util.Assert;
public class DelegatingEntityResolver implements EntityResolver {

	/** Suffix for DTD files */
	public static final String DTD_SUFFIX = ".dtd";

	/** Suffix for schema definition files */
	public static final String XSD_SUFFIX = ".xsd";


	private final EntityResolver dtdResolver;

	private final EntityResolver schemaResolver;


	/**
	 * Create a new DelegatingEntityResolver that delegates to
	 * a default {@link BeansDtdResolver} and a default {@link PluggableSchemaResolver}.
	 * <p>Configures the {@link PluggableSchemaResolver} with the supplied
	 * {@link ClassLoader}.
	 * @param classLoader the ClassLoader to use for loading
	 * (can be <code>null</code>) to use the default ClassLoader)
	 */
	public DelegatingEntityResolver(ClassLoader classLoader) {
		this.dtdResolver = new BeansDtdResolver();
		this.schemaResolver = new PluggableSchemaResolver(classLoader);
	}

	/**
	 * Create a new DelegatingEntityResolver that delegates to
	 * the given {@link EntityResolver EntityResolvers}.
	 * @param dtdResolver the EntityResolver to resolve DTDs with
	 * @param schemaResolver the EntityResolver to resolve XML schemas with
	 */
	public DelegatingEntityResolver(EntityResolver dtdResolver, EntityResolver schemaResolver) {
		Assert.notNull(dtdResolver, "'dtdResolver' is required");
		Assert.notNull(schemaResolver, "'schemaResolver' is required");
		this.dtdResolver = dtdResolver;
		this.schemaResolver = schemaResolver;
	}


	public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
		if (systemId != null) {
			if (systemId.endsWith(DTD_SUFFIX)) {
				return this.dtdResolver.resolveEntity(publicId, systemId);
			}
			else if (systemId.endsWith(XSD_SUFFIX)) {
				return this.schemaResolver.resolveEntity(publicId, systemId);
			}
		}
		return null;
	}

}

 

package org.springframework.beans.factory.xml;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLDecoder;

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

import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;

/**
 * EntityResolver implementation that tries to resolve entity references
 * through a {@link org.springframework.core.io.ResourceLoader} (usually,
 * relative to the resource base of an ApplicationContext), if applicable.
 * Extends {@link DelegatingEntityResolver} to also provide DTD and XSD lookup.
 *
 * <p>Allows to use standard XML entities to include XML snippets into an
 * application context definition, for example to split a large XML file
 * into various modules. The include paths can be relative to the
 * application context's resource base as usual, instead of relative
 * to the JVM working directory (the XML parser's default).
 *
 * <p>Note: In addition to relative paths, every URL that specifies a
 * file in the current system root, i.e. the JVM working directory,
 * will be interpreted relative to the application context too.
 *
 * @author Juergen Hoeller
 * @since 31.07.2003
 * @see org.springframework.core.io.ResourceLoader
 * @see org.springframework.context.ApplicationContext
 */
public class ResourceEntityResolver extends DelegatingEntityResolver {

	private static final Log logger = LogFactory.getLog(ResourceEntityResolver.class);

	private final ResourceLoader resourceLoader;


	/**
	 * Create a ResourceEntityResolver for the specified ResourceLoader
	 * (usually, an ApplicationContext).
	 * @param resourceLoader the ResourceLoader (or ApplicationContext)
	 * to load XML entity includes with
	 */
	public ResourceEntityResolver(ResourceLoader resourceLoader) {
		super(resourceLoader.getClassLoader());
		this.resourceLoader = resourceLoader;
	}


	public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
		InputSource source = super.resolveEntity(publicId, systemId);
		if (source == null && systemId != null) {
			String resourcePath = null;
			try {
				String decodedSystemId = URLDecoder.decode(systemId);
				String givenUrl = new URL(decodedSystemId).toString();
				String systemRootUrl = new File("").toURL().toString();
				// Try relative to resource base if currently in system root.
				if (givenUrl.startsWith(systemRootUrl)) {
					resourcePath = givenUrl.substring(systemRootUrl.length());
				}
			}
			catch (Exception ex) {
				// Typically a MalformedURLException or AccessControlException.
				if (logger.isDebugEnabled()) {
					logger.debug("Could not resolve XML entity [" + systemId + "] against system root URL", ex);
				}
				// No URL (or no resolvable URL) -> try relative to resource base.
				resourcePath = systemId;
			}
			if (resourcePath != null) {
				if (logger.isTraceEnabled()) {
					logger.trace("Trying to locate XML entity [" + systemId + "] as resource [" + resourcePath + "]");
				}
				Resource resource = this.resourceLoader.getResource(resourcePath);
				source = new InputSource(resource.getInputStream());
				source.setPublicId(publicId);
				source.setSystemId(systemId);
				if (logger.isDebugEnabled()) {
					logger.debug("Found XML entity [" + systemId + "]: " + resource);
				}
			}
		}
		return source;
	}

}

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