org.springframework.beans.factory.xml.PluggableSchemaResolver Maven / Gradle / Ivy
/*
* 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
*
* 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.lang.Nullable;
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.
*
* By default, this class will look for mapping files in the classpath using the
* pattern: {@code META-INF/spring.schemas} allowing for multiple files to exist on
* the classpath at any one time.
*
*
The format of {@code META-INF/spring.schemas} is a properties file where each line
* should be of the form {@code systemId=schema-location} where {@code schema-location}
* should also be a schema file in the classpath. Since {@code systemId} is commonly a
* URL, one must be careful to escape any ':' characters which are treated as delimiters
* in properties files.
*
*
The pattern for the mapping files can be overridden 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);
@Nullable
private final ClassLoader classLoader;
private final String schemaMappingsLocation;
/** Stores the mapping of schema URL -> local schema path. */
@Nullable
private volatile Map 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}) to use the default ClassLoader)
* @see PropertiesLoaderUtils#loadAllProperties(String, ClassLoader)
*/
public PluggableSchemaResolver(@Nullable 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}) 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(@Nullable ClassLoader classLoader, String schemaMappingsLocation) {
Assert.hasText(schemaMappingsLocation, "'schemaMappingsLocation' must not be empty");
this.classLoader = classLoader;
this.schemaMappingsLocation = schemaMappingsLocation;
}
@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) {
String resourceLocation = getSchemaMappings().get(systemId);
if (resourceLocation == null && systemId.startsWith("https:")) {
// Retrieve canonical http schema mapping even for https declaration
resourceLocation = getSchemaMappings().get("http:" + systemId.substring(6));
}
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.isTraceEnabled()) {
logger.trace("Found XML schema [" + systemId + "] in classpath: " + resourceLocation);
}
return source;
}
catch (FileNotFoundException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not find XML schema [" + systemId + "]: " + resource, ex);
}
}
}
}
// Fall back to the parser's default behavior.
return null;
}
/**
* Load the specified schema mappings lazily.
*/
private Map getSchemaMappings() {
Map schemaMappings = this.schemaMappings;
if (schemaMappings == null) {
synchronized (this) {
schemaMappings = this.schemaMappings;
if (schemaMappings == null) {
if (logger.isTraceEnabled()) {
logger.trace("Loading schema mappings from [" + this.schemaMappingsLocation + "]");
}
try {
Properties mappings =
PropertiesLoaderUtils.loadAllProperties(this.schemaMappingsLocation, this.classLoader);
if (logger.isTraceEnabled()) {
logger.trace("Loaded schema mappings: " + mappings);
}
schemaMappings = new ConcurrentHashMap<>(mappings.size());
CollectionUtils.mergePropertiesIntoMap(mappings, schemaMappings);
this.schemaMappings = schemaMappings;
}
catch (IOException ex) {
throw new IllegalStateException(
"Unable to load schema mappings from location [" + this.schemaMappingsLocation + "]", ex);
}
}
}
}
return schemaMappings;
}
@Override
public String toString() {
return "EntityResolver using schema mappings " + getSchemaMappings();
}
}