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 *     https://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.i18n.I18n;
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 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 final 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     * Private constructor
052     */
053    private LdapApiServiceFactory()
054    {
055    }
056
057
058    /**
059     * Checks to see if the factory is initialized.
060     *
061     * @return true if initialized, false otherwise
062     */
063    public static boolean isInitialized()
064    {
065        return ldapCodecService != null;
066    }
067
068
069    /**
070     * Checks to see if the factory is using the standalone implementation.
071     *
072     * @return true if using the standalone implementation, false otherwise.
073     */
074    public static boolean isUsingStandaloneImplementation()
075    {
076        if ( !isInitialized() )
077        {
078            String msg = I18n.err( I18n.ERR_05200_NOT_INITIALIZED_YET );
079            LOG.error( msg );
080            throw new IllegalStateException( msg );
081        }
082
083        return usingStandaloneImplementation;
084    }
085
086
087    /**
088     * Gets the singleton instance of the LdapCodecService.
089     *
090     * @return a valid instance implementation based on environment and the 
091     * availability of bindings.
092     */
093    public static LdapApiService getSingleton()
094    {
095        if ( ldapCodecService == null )
096        {
097            initialize( null );
098        }
099
100        return ldapCodecService;
101    }
102
103
104    /**
105     * Initialization can only take place once. There after an exception 
106     * results.
107     * 
108     * @param ldapCodecService The LDAP Codec Service to initialize with.
109     */
110    public static void initialize( LdapApiService ldapCodecService )
111    {
112        /*
113         * If the class member is already set we have problems.
114         */
115
116        if ( LdapApiServiceFactory.ldapCodecService != null )
117        {
118            String msg = I18n.err( I18n.ERR_05201_INSTANCE_ALREADY_SET, LdapApiServiceFactory.class.getName() );
119            LOG.error( msg );
120            throw new IllegalStateException( msg );
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( I18n.err( I18n.ERR_05202_FAILED_TO_INSTANCIATE, e.getMessage() ) );
140            }
141        }
142        else
143        {
144            usingStandaloneImplementation = false;
145            LdapApiServiceFactory.ldapCodecService = ldapCodecService;
146        }
147    }
148}