Package net.sf.jasperreports.engine.util

Source Code of net.sf.jasperreports.engine.util.JRSingletonCache

/*
* JasperReports - Free Java Reporting Library.
* Copyright (C) 2001 - 2009 Jaspersoft Corporation. All rights reserved.
* http://www.jaspersoft.com
*
* Unless you have purchased a commercial license agreement from Jaspersoft,
* the following license terms apply:
*
* This program is part of JasperReports.
*
* JasperReports is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* JasperReports 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.
*
* You should have received a copy of the GNU Lesser General Public License
* along with JasperReports. If not, see <http://www.gnu.org/licenses/>.
*/
package net.sf.jasperreports.engine.util;

import java.util.Map;

import net.sf.jasperreports.engine.JRException;

import org.apache.commons.collections.ReferenceMap;


/**
* Utility to use as a soft cache of singleton instances.
*
* @author Lucian Chirita (lucianc@users.sourceforge.net)
* @version $Id: JRSingletonCache.java 3034 2009-08-27 11:58:04Z teodord $
*/
public class JRSingletonCache
{
  private static final Object CONTEXT_KEY_NULL = new Object();
 
  private final ReferenceMap cache;
  private final Class itf;

  /**
   * Creates a cache of singleton instances.
   *
   * @param itf a interface or class that should be implemented by all classes cached by this object
   */
  public JRSingletonCache(Class itf)
  {
    cache = new ReferenceMap(ReferenceMap.WEAK, ReferenceMap.SOFT);
    this.itf = itf;
  }

  /**
   * Returns the singleton instance corresponding to a class.
   * <p>
   * The instance is first searched into the cache and created if not found.
   * <p>
   * The class is expected to have a no-argument constructor.
   *
   * @param className
   * @return the singleton instance corresponding to a class
   * @throws JRException
   */
  public synchronized Object getCachedInstance(String className) throws JRException
  {
    Map contextCache = getContextInstanceCache();
    Object instance = contextCache.get(className);
    if (instance == null)
    {
      instance = createInstance(className);
      contextCache.put(className, instance);
    }
    return instance;
  }

  protected Object createInstance(String className) throws JRException
  {
    try
    {
      Class clazz = JRClassLoader.loadClassForName(className);
      if (itf != null && !itf.isAssignableFrom(clazz))
      {
        throw new JRException("Class \"" + className + "\" should be compatible with \"" + itf.getName() + "\"");
      }

      return clazz.newInstance();
    }
    catch (ClassNotFoundException e)
    {
      throw new JRException("Class " + className + " not found.", e);
    }
    catch (InstantiationException e)
    {
      throw new JRException("Error instantiating class " + className + ".", e);
    }
    catch (IllegalAccessException e)
    {
      throw new JRException("Error instantiating class " + className + ".", e);
    }
  }

  protected Map getContextInstanceCache()
  {
    Object contextKey = getContextKey();
    Map contextCache = (Map) cache.get(contextKey);
    if (contextCache == null)
    {
      contextCache = new ReferenceMap();
      cache.put(contextKey, contextCache);
    }
    return contextCache;
  }
 
  protected Object getContextKey()
  {
    Object key = Thread.currentThread().getContextClassLoader();
    if (key == null)
    {
      key = CONTEXT_KEY_NULL;
    }
    return key;
  }
}
TOP

Related Classes of net.sf.jasperreports.engine.util.JRSingletonCache

TOP
Copyright © 2018 www.massapi.com. All rights reserved.
All source code are property of their respective owners. Java is a trademark of Sun Microsystems, Inc and owned by ORACLE Inc. Contact coftware#gmail.com.