001/* 
002    Licensed to the Apache Software Foundation (ASF) under one
003    or more contributor license agreements.  See the NOTICE file
004    distributed with this work for additional information
005    regarding copyright ownership.  The ASF licenses this file
006    to you under the Apache License, Version 2.0 (the
007    "License"); you may not use this file except in compliance
008    with the License.  You may obtain a copy of the License at
009
010       http://www.apache.org/licenses/LICENSE-2.0
011
012    Unless required by applicable law or agreed to in writing,
013    software distributed under the License is distributed on an
014    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015    KIND, either express or implied.  See the License for the
016    specific language governing permissions and limitations
017    under the License.  
018 */
019package org.apache.wiki.auth.permissions;
020
021import java.util.WeakHashMap;
022
023import org.apache.wiki.WikiPage;
024
025/**
026 *  Provides a factory for Permission objects.  Since the Permissions are immutable,
027 *  and creating them takes a bit of time, caching them makes sense.
028 *  <p>
029 *  This class stores the permissions in a static HashMap.
030 *  @since 2.5.54
031 */
032public final class PermissionFactory
033{
034    /**
035     *  Prevent instantiation.
036     */
037    private PermissionFactory() {}
038    
039    /**
040     *  This is a WeakHashMap<Integer,PagePermission>, which stores the
041     *  cached page permissions.
042     */
043    private static WeakHashMap<Integer, PagePermission> c_cache = new WeakHashMap<Integer, PagePermission>();
044    
045    /**
046     *  Get a permission object for a WikiPage and a set of actions.
047     *  
048     *  @param page The page object.
049     *  @param actions A list of actions.
050     *  @return A PagePermission object, presenting this page+actions combination.
051     */
052    public static PagePermission getPagePermission( WikiPage page, String actions )
053    {
054        return getPagePermission( page.getWiki(), page.getName(), actions );
055    }
056    
057    /**
058     *  Get a permission object for a WikiPage and a set of actions.
059     *  
060     *  @param page The name of the page.
061     *  @param actions A list of actions.
062     *  @return A PagePermission object, presenting this page+actions combination.
063     */
064    public static PagePermission getPagePermission( String page, String actions )
065    {
066        return getPagePermission( "", page, actions );
067    }
068
069    /**
070     *  Get a page permission based on a wiki, page, and actions.
071     *  
072     *  @param wiki The name of the wiki. Can be an empty string, but must not be null.
073     *  @param page The page name
074     *  @param actions A list of actions.
075     *  @return A PagePermission object.
076     */
077    private static PagePermission getPagePermission( String wiki, String page, String actions )
078    {
079        PagePermission perm;
080        //
081        //  Since this is pretty speed-critical, we try to avoid the StringBuffer creation
082        //  overhead by XORring the hashcodes.  However, if page name length > 32 characters,
083        //  this might result in two same hashCodes.
084        //  FIXME: Make this work for page-name lengths > 32 characters (use the alt implementation
085        //         if page.length() > 32?)
086        // Alternative implementation below, but it does create an extra StringBuffer.
087        //String         key = wiki+":"+page+":"+actions;
088        
089        Integer key = wiki.hashCode() ^ page.hashCode() ^ actions.hashCode();
090   
091        //
092        //  It's fine if two threads update the cache, since the objects mean the same
093        //  thing anyway.  And this avoids nasty blocking effects.
094        //
095        synchronized( c_cache )
096        {
097            perm = c_cache.get( key );
098        }
099        
100        if( perm == null )
101        {
102            if( wiki.length() > 0 ) page = wiki+":"+page;
103            perm = new PagePermission( page, actions );
104            
105            synchronized( c_cache )
106            {
107                c_cache.put( key, perm );
108            }
109        }
110        
111        return perm;
112    }
113
114}