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ResourceLoader.java
/*
 * This program is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 * or from the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * Copyright (c) 2006 - 2009 Pentaho Corporation and Contributors.  All rights reserved.
 */

package org.pentaho.reporting.libraries.resourceloader;

import java.util.Map;
import java.net.URL;

/**
 * A resource loader knows how to get binary rawdata from a location specified
 * by an resource key. A resource key is a wrapper around any kind of data that
 * is suitable to identify a resource location. The resource key can also hold
 * configuration data for the factory.
 *
 * If the storage system is hierarchical, a new resource key can be derived from
 * a given path-string.
 *
 * @author Thomas Morgner
 */
00034 public interface ResourceLoader
{
  /**
   * Checks, whether this resource loader implementation was responsible for
   * creating this key.
   *
   * @param key the key that should be tested.
   * @return true, if the key is supported.
   */
  public boolean isSupportedKey (ResourceKey key);

  /**
   * Creates a new resource key from the given object and the factory keys.
   *
   * @param value the key value.
   * @param factoryKeys optional parameter map (can be null).
   * @return the created key or null, if the format was not recognized.
   * @throws ResourceKeyCreationException if creating the key failed.
   */
  public ResourceKey createKey (Object value,
                                Map factoryKeys)
      throws ResourceKeyCreationException;

  /**
   * Derives a new resource key from the given key. If neither a path nor new
   * factory-keys are given, the parent key is returned.
   *
   * @param parent the parent
   * @param path the derived path (can be null).
   * @param factoryKeys the optional factory keys (can be null).
   * @return the derived key.
   * @throws ResourceKeyCreationException if the key cannot be derived for any
   * reason.
   */
  public ResourceKey deriveKey (ResourceKey parent,
                                String path,
                                Map factoryKeys)
      throws ResourceKeyCreationException;

  /**
   * Loads the binary data represented by this key.
   *
   * @param key
   * @return
   * @throws ResourceLoadingException
   */
  public ResourceData load (final ResourceKey key)
      throws ResourceLoadingException;

  /**
   * Generates a <code>URL</code> version of the supplied <code>ResourceKey</code>.
   * 
   * @param key the <code>ResourceKey</code> from which a <code>URL</code> will be created
   * @return the URL representation of the <code>ResourceKey</code>
   */
  public URL toURL (ResourceKey key);
  
  
  /**
   * Determines if the resource loader is capable of deserializing the 
   * serialized version of the ResourceKey.
   * @param data the serialized version of the resource key
   * @return <code>true</code> if this <code>ResourceLoader</code> is capable of deserializing the
   *   serialized version of this resource key, <code>false</code> otherwise.
   */
  public boolean isSupportedDeserializer(final String data);
  
  
  /**
   * Serializes the resource key to a String representation which can be recreated
   * using the <code>deserialize(ResourceKey)<code> method. 
   * @return a <code>String<code> which is a serialized version of the <code>ResourceKey</code>
   * @throws ResourceException indicates an error serializing the resource key
   * @param bundleKey
   * @param key
   */
  public String serialize(final ResourceKey bundleKey, final ResourceKey key) throws ResourceException;
  
  /**
   * Creates a <code>ResourceKey</code> based off the <code>String</code> representation
   * of the key. The <code>String</code> should have been created using the <code>serialize</code>
   * method.
   * 
   * @param bundleKey
   *@param stringKey the <code>String</code> representation of the <code>ResourceKey</code>  @return a <code>ResourceKey</code> which matches the <code>String</code> representation
   * @throws ResourceKeyCreationException indicates an error occurred in the creation or
   *   deserialization of the <code>ResourceKey</code>
   */
  public ResourceKey deserialize(final ResourceKey bundleKey, final String stringKey) throws ResourceKeyCreationException;
}

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