hierarchicalconfiguration.java

这是一个segy数据显示程序

/* ========================================================================
 * JCommon : a free general purpose class library for the Java(tm) platform
 * ========================================================================
 *
 * (C) Copyright 2000-2004, by Object Refinery Limited and Contributors.
 * 
 * Project Info:  http://www.jfree.org/jcommon/index.html
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 * 
 * ------------------------------
 * HierarchicalConfiguration.java
 * ------------------------------
 * (C) Copyright 2004, by Object Refinery Limited.
 *
 * Original Author:  Thomas Morgner;
 * Contributor(s):   David Gilbert (for Object Refinery Limited);
 *
 * $Id: HierarchicalConfiguration.java,v 1.2 2004/06/07 14:44:56 mungady Exp $
 *
 * Changes
 * -------
 * 07-Jun-2004 : Added JCommon header (DG);
 *
 */

package org.jfree.base.config;

import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Properties;
import java.util.TreeSet;

/**
 * A hierarchical configuration.
 */
public class HierarchicalConfiguration implements ModifiableConfiguration 
{
  private Properties configuration;

  /** The parent configuration (null if this is the root configuration). */
  private transient ModifiableConfiguration parentConfiguration;

  /**
   * Creates a new configuration.
   */
  public HierarchicalConfiguration () {
    configuration = new Properties();
  }

  /**
   * Creates a new configuration.
   * 
   * @param parentConfiguration  the parent configuration.
   */
  public HierarchicalConfiguration (final ModifiableConfiguration parentConfiguration) {
    this();
    this.parentConfiguration = parentConfiguration;
  }

  /**
   * Returns the configuration property with the specified key.
   *
   * @param key  the property key.
   *
   * @return the property value.
   */
  public String getConfigProperty(final String key)
  {
    return getConfigProperty(key, null);
  }

  /**
   * Returns the configuration property with the specified key
   * (or the specified default value if there is no such property).
   * <p>
   * If the property is not defined in this configuration, the code
   * will lookup the property in the parent configuration.
   *
   * @param key  the property key.
   * @param defaultValue  the default value.
   *
   * @return the property value.
   */
  public String getConfigProperty(final String key, final String defaultValue)
  {
    String value = configuration.getProperty(key);
    if (value == null)
    {
      if (isRootConfig())
      {
        value = defaultValue;
      }
      else
      {
        value = parentConfiguration.getConfigProperty(key, defaultValue);
      }
    }
    return value;
  }

  /**
   * Sets a configuration property.
   *
   * @param key  the property key.
   * @param value  the property value.
   */
  public void setConfigProperty(final String key, final String value)
  {
    if (key == null)
    {
      throw new NullPointerException();
    }

    if (value == null)
    {
      configuration.remove(key);
    }
    else
    {
      configuration.setProperty(key, value);
    }
  }

  /**
   * Returns true if this object has no parent.
   *
   * @return true, if this report is the root configuration, false otherwise.
   */
  private boolean isRootConfig()
  {
    return parentConfiguration == null;
  }

  /**
   * Checks, whether the given key is localy defined in this instance or
   * whether the key's value is inherited.
   *
   * @param key the key that should be checked.
   * @return true, if the key is defined locally, false otherwise.
   */
  public boolean isLocallyDefined (final String key)
  {
    return configuration.containsKey(key);
  }

  /**
   * Returns the collection of properties for the configuration.
   *
   * @return the properties.
   */
  protected Properties getConfiguration()
  {
    return configuration;
  }

  /**
   * The new configuartion will be inserted into the list of report configuration,
   * so that this configuration has the given report configuration instance as parent.
   *
   * @param config the new report configuration.
   */
  public void insertConfiguration(final HierarchicalConfiguration config)
  {
    config.setParentConfig(getParentConfig());
    setParentConfig(config);
  }

  /**
   * Set the parent configuration. The parent configuration is queried, if the
   * requested configuration values was not found in this report configuration.
   *
   * @param config  the parent configuration.
   */
  protected void setParentConfig(final ModifiableConfiguration config)
  {
    if (parentConfiguration == this)
    {
      throw new IllegalArgumentException("Cannot add myself as parent configuration.");
    }
    parentConfiguration = config;
  }

  /**
   * Returns the parent configuration. The parent configuration is queried, if the
   * requested configuration values was not found in this report configuration.
   *
   * @return the parent configuration.
   */
  protected ModifiableConfiguration getParentConfig()
  {
    return parentConfiguration;
  }

  /**
   * Returns all defined configuration properties for the report. The enumeration
   * contains all keys of the changed properties, properties set from files or
   * the system properties are not included.
   *
   * @return all defined configuration properties for the report.
   */
  public Enumeration getConfigProperties()
  {
    return configuration.keys();
  }

  /**
   * Searches all property keys that start with a given prefix.
   *
   * @param prefix the prefix that all selected property keys should share
   * @return the properties as iterator.
   */
  public Iterator findPropertyKeys(final String prefix)
  {
    final TreeSet keys = new TreeSet();
    collectPropertyKeys(prefix, this, keys);
    return Collections.unmodifiableSet(keys).iterator();
  }

  /**
   * Collects property keys from this and all parent report configurations, which
   * start with the given prefix.
   *
   * @param prefix the prefix, that selects the property keys.
   * @param config the currently processed report configuration.
   * @param collector the target list, that should receive all valid keys.
   */
  private void collectPropertyKeys(final String prefix, final ModifiableConfiguration config,
                                   final TreeSet collector)
  {
    final Enumeration enum = config.getConfigProperties();
    while (enum.hasMoreElements())
    {
      final String key = (String) enum.nextElement();
      if (key.startsWith(prefix))
      {
        if (collector.contains(key) == false)
        {
          collector.add(key);
        }
      }
    }

    if (config instanceof HierarchicalConfiguration)
    {
      final HierarchicalConfiguration hconfig = (HierarchicalConfiguration) config;
      if (hconfig.parentConfiguration != null)
      {
        collectPropertyKeys(prefix, hconfig.parentConfiguration, collector);
      }
    }
  }


}