| package org.apache.turbine.util; |
| |
| /* ==================================================================== |
| * The Apache Software License, Version 1.1 |
| * |
| * Copyright (c) 2001-2003 The Apache Software Foundation. All rights |
| * reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, |
| * if any, must include the following acknowledgment: |
| * "This product includes software developed by the |
| * Apache Software Foundation (http://www.apache.org/)." |
| * Alternately, this acknowledgment may appear in the software itself, |
| * if and wherever such third-party acknowledgments normally appear. |
| * |
| * 4. The names "Apache" and "Apache Software Foundation" and |
| * "Apache Turbine" must not be used to endorse or promote products |
| * derived from this software without prior written permission. For |
| * written permission, please contact apache@apache.org. |
| * |
| * 5. Products derived from this software may not be called "Apache", |
| * "Apache Turbine", nor may "Apache" appear in their name, without |
| * prior written permission of the Apache Software Foundation. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
| * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation. For more |
| * information on the Apache Software Foundation, please see |
| * <http://www.apache.org/>. |
| */ |
| |
| import java.util.Collection; |
| import java.util.Hashtable; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * A {@link java.util.Hashtable} whose keys are sequenced. The |
| * sequencing of the keys allow easy access to the values in the order |
| * which they were added in. This class is thread safe. |
| * <p> |
| * Implementing the List interface is not possible due to a instance |
| * method name clash between the Collection and the List interface: |
| * |
| * <table> |
| * <tr><td>Collections</td><td>boolean remove(Object o)</td></tr> |
| * <tr><td>Lists</td><td>Object remove(Object o)</td></tr> |
| * </table> |
| * |
| * So one cannot implement both interfaces at the same, which is unfortunate |
| * because the List interface would be very nice in conjuction with Velocity. |
| * <p> |
| * A slightly more complex implementation and interface could involve |
| * the use of a list of <code>Map.Entry</code> objects. |
| * |
| * @author <a href="mailto:dlr@collab.net">Daniel Rall</a> |
| * @version $Id$ |
| * @deprecated Use SequencedHashMap from the commons collections. |
| */ |
| public class SequencedHashtable extends Hashtable |
| { |
| /** |
| * Indicator for an unknown index. |
| */ |
| private static final int UNKNOWN_INDEX = -1; |
| |
| /** |
| * The sequence used to keep track of the hash keys. Younger objects are |
| * kept towards the end of the list. Does not allow duplicates. |
| */ |
| private LinkedList keySequence; |
| |
| /** |
| * Creates a new instance with default storage. |
| */ |
| public SequencedHashtable() |
| { |
| keySequence = new LinkedList(); |
| } |
| |
| /** |
| * Creates a new instance with the specified storage. |
| * |
| * @param size The storage to allocate up front. |
| */ |
| public SequencedHashtable(int size) |
| { |
| super(size); |
| keySequence = new LinkedList(); |
| } |
| |
| /** |
| * Clears all elements. |
| */ |
| public synchronized void clear() |
| { |
| super.clear(); |
| keySequence.clear(); |
| } |
| |
| /** |
| * Creates a shallow copy of this object, preserving the internal |
| * structure by copying only references. The keys, values, and |
| * sequence are not <code>clone()</code>'d. |
| * |
| * @return A clone of this instance. |
| */ |
| public synchronized Object clone() |
| { |
| SequencedHashtable seqHash = (SequencedHashtable) super.clone(); |
| seqHash.keySequence = (LinkedList) keySequence.clone(); |
| return seqHash; |
| } |
| |
| /** |
| * Returns the key at the specified index. |
| */ |
| public Object get(int index) |
| { |
| return keySequence.get(index); |
| } |
| |
| /** |
| * Returns the value at the specified index. |
| */ |
| public Object getValue(int index) |
| { |
| return get(get(index)); |
| } |
| |
| /** |
| * Returns the index of the specified key. |
| */ |
| public int indexOf(Object key) |
| { |
| return keySequence.indexOf(key); |
| } |
| |
| /** |
| * Returns a key iterator. |
| */ |
| public Iterator iterator() |
| { |
| return keySequence.iterator(); |
| } |
| |
| /** |
| * Returns the last index of the specified key. |
| */ |
| public int lastIndexOf(Object key) |
| { |
| return keySequence.lastIndexOf(key); |
| } |
| |
| /** |
| * Returns the ordered sequence of keys. |
| * |
| * This method is meant to be used for retrieval of Key / Value pairs |
| * in e.g. Velocity: |
| * <PRE> |
| * ## $table contains a sequenced hashtable |
| * #foreach ($key in $table.sequence()) |
| * <TR> |
| * <TD>Key: $key</TD> |
| * </TD>Value: $table.get($key)</TD> |
| * </TR> |
| * #end |
| * </PRE> |
| * |
| * @return The ordered list of keys. |
| */ |
| public List sequence() |
| { |
| return keySequence; |
| } |
| |
| /** |
| * Stores the provided key/value pair. Freshens the sequence of existing |
| * elements. |
| * |
| * @param key The key to the provided value. |
| * @param value The value to store. |
| * @return The previous value for the specified key, or |
| * <code>null</code> if none. |
| */ |
| public synchronized Object put(Object key, Object value) |
| { |
| Object prevValue = super.put(key, value); |
| freshenSequence(key, prevValue); |
| return prevValue; |
| } |
| |
| /** |
| * Freshens the sequence of the element <code>value</code> if |
| * <code>value</code> is not <code>null</code>. |
| * |
| * @param key The key whose sequence to freshen. |
| * @param value The value whose existance to check before removing the old |
| * key sequence. |
| */ |
| protected void freshenSequence(Object key, Object value) |
| { |
| if (value != null) |
| { |
| // Freshening existing element's sequence. |
| keySequence.remove(key); |
| } |
| keySequence.add(key); |
| } |
| |
| /** |
| * Stores the provided key/value pairs. |
| * |
| * @param t The key/value pairs to store. |
| */ |
| public synchronized void putAll(Map t) |
| { |
| Set set = t.entrySet(); |
| for (Iterator iter = set.iterator(); iter.hasNext();) |
| { |
| Map.Entry e = (Map.Entry) iter.next(); |
| put(e.getKey(), e.getValue()); |
| } |
| } |
| |
| /** |
| * Removes the element at the specified index. |
| * |
| * @param index The index of the object to remove. |
| * @return The previous value coressponding the <code>key</code>, or |
| * <code>null</code> if none existed. |
| */ |
| public Object remove(int index) |
| { |
| return remove(index, null); |
| } |
| |
| /** |
| * Removes the element with the specified key. |
| * |
| * @param key The <code>Map</code> key of the object to remove. |
| * @return The previous value coressponding the <code>key</code>, or |
| * <code>null</code> if none existed. |
| */ |
| public Object remove(Object key) |
| { |
| return remove(UNKNOWN_INDEX, key); |
| } |
| |
| /** |
| * Removes the element with the specified key or index. |
| * |
| * @param index The index of the object to remove, or |
| * <code>UNKNOWN_INDEX</code> if not known. |
| * @param key The <code>Map</code> key of the object to remove. |
| * @return The previous value coressponding the <code>key</code>, or |
| * <code>null</code> if none existed. |
| */ |
| private final synchronized Object remove(int index, Object key) |
| { |
| if (index == UNKNOWN_INDEX) index = indexOf(key); |
| if (key == null) key = get(index); |
| if (index != UNKNOWN_INDEX) keySequence.remove(index); |
| return super.remove(key); |
| } |
| |
| /** |
| * Slightly cheaper implementation of <code>values()</code> method. |
| */ |
| public Collection values() |
| { |
| return keySequence; |
| } |
| } |