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org/springframework/beans/factory/xml/DelegatingEntityResolver.java
/*
 * 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.IOException;

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

import org.springframework.util.Assert;

/**
 {@link EntityResolver} implementation that delegates to a {@link BeansDtdResolver}
 * and a {@link PluggableSchemaResolver} for DTDs and XML schemas, respectively.
 *
 @author Rob Harrop
 @author Juergen Hoeller
 @author Rick Evans
 @since 2.0
 @see BeansDtdResolver
 @see PluggableSchemaResolver
 */
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 systemIdthrows 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;
  }


  @Override
  public String toString() {
    return "EntityResolver delegating " + XSD_SUFFIX + " to " this.schemaResolver +
        " and " + DTD_SUFFIX +  " to " this.dtdResolver;
  }

}