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