/*
* Copyright 2002-2009 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
*
* 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.springframework.beans.factory.xml;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
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.core.io.support.PropertiesLoaderUtils;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
/**
* {@link EntityResolver} implementation that attempts to resolve schema URLs into
* local {@link ClassPathResource classpath resources} using a set of mappings files.
*
* <p>By default, this class will look for mapping files in the classpath using the pattern:
* <code>META-INF/spring.schemas</code> allowing for multiple files to exist on the
* classpath at any one time.
*
* The format of <code>META-INF/spring.schemas</code> is a properties
* file where each line should be of the form <code>systemId=schema-location</code>
* where <code>schema-location</code> should also be a schema file in the classpath.
* Since systemId is commonly a URL, one must be careful to escape any ':' characters
* which are treated as delimiters in properties files.
*
* <p>The pattern for the mapping files can be overidden using the
* {@link #PluggableSchemaResolver(ClassLoader, String)} constructor
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public class PluggableSchemaResolver implements EntityResolver {
/**
* The location of the file that defines schema mappings.
* Can be present in multiple JAR files.
*/
public static final String DEFAULT_SCHEMA_MAPPINGS_LOCATION = "META-INF/spring.schemas";
private static final Log logger = LogFactory.getLog(PluggableSchemaResolver.class);
private final ClassLoader classLoader;
private final String schemaMappingsLocation;
/** Stores the mapping of schema URL -> local schema path */
private volatile Map<String, String> schemaMappings;
/**
* Loads the schema URL -> schema file location mappings using the default
* mapping file pattern "META-INF/spring.schemas".
* @param classLoader the ClassLoader to use for loading
* (can be <code>null</code>) to use the default ClassLoader)
* @see PropertiesLoaderUtils#loadAllProperties(String, ClassLoader)
*/
public PluggableSchemaResolver(ClassLoader classLoader) {
this.classLoader = classLoader;
this.schemaMappingsLocation = DEFAULT_SCHEMA_MAPPINGS_LOCATION;
}
/**
* Loads the schema URL -> schema file location mappings using the given
* mapping file pattern.
* @param classLoader the ClassLoader to use for loading
* (can be <code>null</code>) to use the default ClassLoader)
* @param schemaMappingsLocation the location of the file that defines schema mappings
* (must not be empty)
* @see PropertiesLoaderUtils#loadAllProperties(String, ClassLoader)
*/
public PluggableSchemaResolver(ClassLoader classLoader, String schemaMappingsLocation) {
Assert.hasText(schemaMappingsLocation, "'schemaMappingsLocation' must not be empty");
this.classLoader = classLoader;
this.schemaMappingsLocation = schemaMappingsLocation;
}
public InputSource resolveEntity(String publicId, 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) {
String resourceLocation = getSchemaMappings().get(systemId);
if (resourceLocation != null) {
Resource resource = new ClassPathResource(resourceLocation, this.classLoader);
try {
InputSource source = new InputSource(resource.getInputStream());
source.setPublicId(publicId);
source.setSystemId(systemId);
if (logger.isDebugEnabled()) {
logger.debug("Found XML schema [" + systemId + "] in classpath: " + resourceLocation);
}
return source;
}
catch (FileNotFoundException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Couldn't find XML schema [" + systemId + "]: " + resource, ex);
}
}
}
}
return null;
}
/**
* Load the specified schema mappings lazily.
*/
private Map<String, String> getSchemaMappings() {
if (this.schemaMappings == null) {
synchronized (this) {
if (this.schemaMappings == null) {
if (logger.isDebugEnabled()) {
logger.debug("Loading schema mappings from [" + this.schemaMappingsLocation + "]");
}
try {
Properties mappings =
PropertiesLoaderUtils.loadAllProperties(this.schemaMappingsLocation, this.classLoader);
if (logger.isDebugEnabled()) {
logger.debug("Loaded schema mappings: " + mappings);
}
Map<String, String> schemaMappings = new ConcurrentHashMap<String, String>();
CollectionUtils.mergePropertiesIntoMap(mappings, schemaMappings);
this.schemaMappings = schemaMappings;
}
catch (IOException ex) {
throw new IllegalStateException(
"Unable to load schema mappings from location [" + this.schemaMappingsLocation + "]", ex);
}
}
}
}
return this.schemaMappings;
}
@Override
public String toString() {
return "EntityResolver using mappings " + getSchemaMappings();
}
}
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