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 *
019 */
020package org.apache.directory.api.ldap.codec.api;
021
022
023import org.slf4j.Logger;
024import org.slf4j.LoggerFactory;
025
026
027/**
028 * A factory that allows callers a means to get a handle on an LdapCodecService
029 * implementation regardless of the environment in which they're accessing it.
030 * In an OSGi environment, the BundleActivator binds the LdapCodecService 
031 * class member forever to the DefaultLdapCodecService. If in 
032 * 
033 * In a standard standalone mode, the Bundle
034 *
035 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
036 */
037public final class LdapApiServiceFactory
038{
039    /** Logger for this class */
040    private static final Logger LOG = LoggerFactory.getLogger( LdapApiServiceFactory.class );
041
042    /** The LdapCodecService singleton bound to this factory */
043    private static LdapApiService ldapCodecService;
044
045    /** Whether or not the standalone implementation is being used */
046    private static boolean usingStandaloneImplementation;
047
048
049    /**
050     * Private constructor
051     */
052    private LdapApiServiceFactory()
053    {
054    }
055
056
057    /**
058     * Checks to see if the factory is initialized.
059     *
060     * @return true if initialized, false otherwise
061     */
062    public static boolean isInitialized()
063    {
064        return ldapCodecService != null;
065    }
066
067
068    /**
069     * Checks to see if the factory is using the standalone implementation.
070     *
071     * @return true if using the standalone implementation, false otherwise.
072     */
073    public static boolean isUsingStandaloneImplementation()
074    {
075        if ( !isInitialized() )
076        {
077            String msg = "Not initialized yet!";
078            LOG.error( msg );
079            throw new IllegalStateException( msg );
080        }
081
082        return usingStandaloneImplementation;
083    }
084
085
086    /**
087     * Gets the singleton instance of the LdapCodecService.
088     *
089     * @return a valid instance implementation based on environment and the 
090     * availability of bindings.
091     */
092    public static LdapApiService getSingleton()
093    {
094        if ( ldapCodecService == null )
095        {
096            initialize( null );
097        }
098
099        return ldapCodecService;
100    }
101
102
103    /**
104     * Initialization can only take place once. There after an exception 
105     * results.
106     * 
107     * @param ldapCodecService The LDAP Codec Service to initialize with.
108     */
109    public static void initialize( LdapApiService ldapCodecService )
110    {
111        /*
112         * If the class member is already set we have problems.
113         */
114
115        if ( LdapApiServiceFactory.ldapCodecService != null )
116        {
117            StringBuilder sb = new StringBuilder( "The LdapCodecService is already set to an instance of " );
118            sb.append( LdapApiServiceFactory.class.getName() );
119            LOG.error( sb.toString() );
120            throw new IllegalStateException( sb.toString() );
121        }
122
123        /*
124         * If the argument is null, then we attempt discovery
125         */
126
127        if ( ldapCodecService == null )
128        {
129            try
130            {
131                @SuppressWarnings("unchecked")
132                Class<? extends LdapApiService> serviceClass = ( Class<? extends LdapApiService> )
133                    Class.forName( "org.apache.directory.api.ldap.codec.standalone.StandaloneLdapApiService" );
134                LdapApiServiceFactory.ldapCodecService = serviceClass.newInstance();
135                usingStandaloneImplementation = true;
136            }
137            catch ( Exception e )
138            {
139                LOG.error( "Failed to instantiate a viable instance, instantiating new instance of ", e );
140            }
141        }
142        else
143        {
144            usingStandaloneImplementation = false;
145            LdapApiServiceFactory.ldapCodecService = ldapCodecService;
146        }
147    }
148}