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AbstractResourceFactory.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.factory;

import java.util.HashSet;
import java.util.Iterator;
import java.util.TreeSet;

import org.pentaho.reporting.libraries.resourceloader.LibLoaderBoot;
import org.pentaho.reporting.libraries.resourceloader.Resource;
import org.pentaho.reporting.libraries.resourceloader.ResourceCreationException;
import org.pentaho.reporting.libraries.resourceloader.ResourceData;
import org.pentaho.reporting.libraries.resourceloader.ResourceFactory;
import org.pentaho.reporting.libraries.resourceloader.ResourceLoadingException;
import org.pentaho.reporting.libraries.resourceloader.ResourceKey;
import org.pentaho.reporting.libraries.resourceloader.ResourceManager;
import org.pentaho.reporting.libraries.resourceloader.ContentNotRecognizedException;
import org.pentaho.reporting.libraries.base.util.ObjectUtilities;
import org.pentaho.reporting.libraries.base.config.Configuration;

/**
 * Creation-Date: 05.04.2006, 16:58:57
 *
 * @author Thomas Morgner
 */
00041 public abstract class AbstractResourceFactory implements ResourceFactory
{

00044   private static class ResourceFactoryEntry implements Comparable
  {
    private FactoryModule module;
    private int weight;

    private ResourceFactoryEntry(final FactoryModule module, final int weight)
    {
      this.module = module;
      this.weight = weight;
    }

    public FactoryModule getModule()
    {
      return module;
    }

    public int getWeight()
    {
      return weight;
    }

    public boolean equals(final Object o)
    {
      if (this == o)
      {
        return true;
      }
      if (o == null || getClass() != o.getClass())
      {
        return false;
      }

      final ResourceFactoryEntry that = (ResourceFactoryEntry) o;

      if (weight != that.weight)
      {
        return false;
      }
      if (module != null ? !module.equals(that.module) : that.module != null)
      {
        return false;
      }

      return true;
    }

    public int hashCode()
    {
      int result;
      result = (module != null ? module.hashCode() : 0);
      result = 31 * result + weight;
      return result;
    }

    /**
     * Compares this object with the specified object for order.  Returns a
     * negative integer, zero, or a positive integer as this object is less than,
     * equal to, or greater than the specified object.<p>
     *
     * "Note: this class has a natural ordering that is inconsistent with
     * equals."
     *
     * @param o the Object to be compared.
     * @return a negative integer, zero, or a positive integer as this object is
     *         less than, equal to, or greater than the specified object.
     * @throws ClassCastException if the specified object's type prevents it from
     *                            being compared to this Object.
     */
00112     public int compareTo(final Object o)
    {
      final ResourceFactoryEntry entry = (ResourceFactoryEntry) o;
      // the order is intentionally reveresed, so that a sorted set has the best
      // fit as first entry.
      if (weight == entry.weight)
      {
        return 0;
      }
      if (weight < entry.weight)
      {
        return -1;
      }
      return 1;
    }
  }

  /** The available factory methods. */
00130   private HashSet factoryModules;
  /** Which type of objects do we create here? */
00132   private Class factoryType;

  protected AbstractResourceFactory(final Class factoryType)
  {
    if (factoryType == null)
    {
      throw new NullPointerException();
    }
    this.factoryType = factoryType;
    this.factoryModules = new HashSet();
  }

00144   public Class getFactoryType()
  {
    return factoryType;
  }

00149   public void initializeDefaults ()
  {
    final String type = getFactoryType().getName();
    final String prefix = CONFIG_PREFIX + type;
    final Configuration config = LibLoaderBoot.getInstance().getGlobalConfig();
    final Iterator itType = config.findPropertyKeys(prefix);
    while (itType.hasNext())
    {
      final String key = (String) itType.next();
      final String modClass = config.getConfigProperty(key);
      final Object maybeFactory = ObjectUtilities.loadAndInstantiate
              (modClass, AbstractResourceFactory.class, FactoryModule.class);
      if (maybeFactory instanceof FactoryModule == false)
      {
        continue;
      }
      registerModule((FactoryModule) maybeFactory);
    }
  }

  public synchronized boolean registerModule(final String className)
  {
    try
    {
      final ClassLoader loader = ObjectUtilities.getClassLoader(getClass());
      final Class c = Class.forName(className, false, loader);
      registerModule((FactoryModule) c.newInstance());
      return true;
    }
    catch (Exception e)
    {
      return false;
    }
  }

  public synchronized void registerModule(final FactoryModule module)
  {
    if (factoryModules.contains(module))
    {
      return;
    }
    factoryModules.add(module);
  }

  /**
   *
   * @param data
   * @param context
   * @return
   * @throws ResourceCreationException
   * @throws ResourceLoadingException
   */
00201   public synchronized Resource create(final ResourceManager manager,
                                      final ResourceData data,
                                      final ResourceKey context)
          throws ResourceCreationException, ResourceLoadingException
  {
    final TreeSet sortedEntries = new TreeSet();
    final Iterator factoryModulesIt = factoryModules.iterator();
    while (factoryModulesIt.hasNext())
    {
      final FactoryModule mod = (FactoryModule) factoryModulesIt.next();
      final int weight = mod.canHandleResource(manager, data);
      if (weight >= 0)
      {
        sortedEntries.add(new ResourceFactoryEntry(mod, weight));
      }
    }

    final Iterator it = sortedEntries.iterator();
    while (it.hasNext())
    {
      final ResourceFactoryEntry entry = (ResourceFactoryEntry) it.next();
      try
      {
        return entry.getModule().create(manager, data, context);
      }
      catch(Exception ex)
      {
        // ok, that one failed, try the next one ...
      }
    }
    throw new ContentNotRecognizedException
            ("No valid handler for the given content.");
  }
}

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