001// Copyright 2004, 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.hivemind;
016
017import java.net.URL;
018import java.util.Locale;
019
020/**
021 * Describes the location of a resource, such as a module deployment
022 * descriptor, or a messages file.
023 * 
024 * <p>
025 * Resources may be either base or localized.  A localized
026 * version of a base resource may be obtained
027 * via {@link #getLocalization(Locale)}.
028 * 
029 * <p>
030 * Resource locations are used as Map keys, they must 
031 * implement {@link java.lang.Object#hashCode()} and
032 * {@link java.lang.Object#equals(java.lang.Object)}
033 * properly.
034 * 
035 * <p>
036 * Resource locations are valid even if the corresponding
037 * resource <i>doesn't exist</i>.  To verify if a localization
038 * actually exists, use {@link #getResourceURL()}, which returns
039 * null if the resource doesn't exist.  {@link #getLocalization(Locale)}
040 * returns only real resource locations, where the resource exists.
041 * 
042 * <p>
043 * Folders must be represented with a trailing slash.
044 *
045 * @author Howard Lewis Ship
046 *
047 **/
048
049public interface Resource
050{
051    /**
052     * Returns a URL for the resource.
053     * 
054     * @return the URL for the resource if it exists, or null if it does not
055     * 
056     */
057    
058    public URL getResourceURL();
059    
060    /**
061     * Returns the file name portion of the resource location.
062     * 
063     */
064    
065    public String getName();
066    
067    /**
068     * Returns a localized version of this resource (or this resource, if no
069     * appropriate localization is found).  Should only be invoked
070     * on a base resource.
071     * 
072     * @param locale to localize for, or null for no localization.
073     * @return a localized version of this resource, of null if the resource
074     * itself does not exist.
075     * 
076     */
077    
078    public Resource getLocalization(Locale locale);
079    
080    /**
081     * Returns at a relative location to this resource.  
082     * The new resource may or may not exist; this can be determined
083     * via {@link #getResourceURL()}.
084     * 
085     * @param name name of new resource, possibly as a relative path, or
086     * as an absolute path (starting with a slash).
087     * 
088     */
089    
090    public Resource getRelativeResource(String name);
091    
092    /**
093     * Returns the path that represents the resource.  This should 
094     * only be used when the type of resource is known.
095     * 
096     */
097    
098    public String getPath();
099
100    /**
101     * Returns the locale for which this resource has been localized 
102     * or null if the resource has not been localized. This should 
103     * only be used when the type of resource is known.
104     *
105     * This locale is the same or more general than the locale for which localization 
106     * was requested. For example, if the requested locale was en_US, but only the file 
107     * Home_en was found, this locale returned would be en. 
108     */
109    
110    public Locale getLocale();
111}