001    /*
002     * Copyright 2009-2016 UnboundID Corp.
003     * All Rights Reserved.
004     */
005    /*
006     * Copyright (C) 2009-2016 UnboundID Corp.
007     *
008     * This program is free software; you can redistribute it and/or modify
009     * it under the terms of the GNU General Public License (GPLv2 only)
010     * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
011     * as published by the Free Software Foundation.
012     *
013     * This program is distributed in the hope that it will be useful,
014     * but WITHOUT ANY WARRANTY; without even the implied warranty of
015     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
016     * GNU General Public License for more details.
017     *
018     * You should have received a copy of the GNU General Public License
019     * along with this program; if not, see <http://www.gnu.org/licenses>.
020     */
021    package com.unboundid.ldap.sdk.persist;
022    
023    
024    
025    import java.io.Closeable;
026    import java.io.Serializable;
027    
028    import com.unboundid.ldap.sdk.Entry;
029    import com.unboundid.ldap.sdk.EntrySource;
030    import com.unboundid.ldap.sdk.LDAPEntrySource;
031    import com.unboundid.ldap.sdk.LDAPException;
032    import com.unboundid.ldap.sdk.SearchResult;
033    import com.unboundid.util.ThreadSafety;
034    import com.unboundid.util.ThreadSafetyLevel;
035    
036    import static com.unboundid.ldap.sdk.persist.PersistMessages.*;
037    import static com.unboundid.util.Debug.*;
038    import static com.unboundid.util.StaticUtils.*;
039    
040    
041    
042    /**
043     * This class provides a mechanism for iterating through the objects returned
044     * by a search operation performed using one of the {@code search} methods in
045     * the {@link LDAPPersister} class.  However, it has a couple of notable
046     * differences from a standard Java {@code Iterator} object:
047     * <UL>
048     *   <LI>It does not have a {@code hasNext} method.  Instead, the {@link #next}
049     *       method will return {@code null} when there are no more objects in the
050     *       set of results.</LI>
051     *   <LI>The {@link #next} method may throw an exception if a problem occurs
052     *       while trying to read an entry or decode it as an object of the
053     *       appropriate type.  This does not necessarily mean that the search is
054     *       complete, and the {@link #next} method should be called again to see
055     *       if there are any more objects to retrieve.</LI>
056     *   <LI>If you wish to stop iterating through the results before all of them
057     *       have been retrieved, then you must call the {@link #close} method
058     * </UL>
059     *
060     * @param  <T>  The type of object handled by this class.
061     */
062    @ThreadSafety(level=ThreadSafetyLevel.NOT_THREADSAFE)
063    public final class PersistedObjects<T>
064           implements Serializable, Closeable
065    {
066      /**
067       * The serial version UID for this serializable class.
068       */
069      private static final long serialVersionUID = 7430494946944736169L;
070    
071    
072    
073      // The LDAP entry source that will be used to read matching entries.
074      private final EntrySource entrySource;
075    
076      // The LDAP persister that will be used to decode the entries that are
077      // returned.
078      private final LDAPPersister<T> persister;
079    
080    
081    
082      /**
083       * Creates a new {@code PersistedObjects} object that will read entries from
084       * the provided entry source.
085       *
086       * @param  persister    The persister that will be used to decode entries that
087       *                      are returned.
088       * @param  entrySource  The entry source that will be used to read entries
089       *                      returned from the search.
090       */
091      PersistedObjects(final LDAPPersister<T> persister,
092                       final EntrySource entrySource)
093      {
094        this.persister   = persister;
095        this.entrySource = entrySource;
096      }
097    
098    
099    
100      /**
101       * Retrieves the next object returned from the search request.  This method
102       * may block until the necessary information  has been received from the
103       * server.
104       *
105       * @return  The next object returned from the search request, or {@code null}
106       *          if all objects have been read.
107       *
108       * @throws  LDAPPersistException  If a problem occurs while reading the next
109       *                                entry from the server, or when trying to
110       *                                decode that entry as an object.
111       */
112      public T next()
113             throws LDAPPersistException
114      {
115        final Entry entry;
116        try
117        {
118          entry = entrySource.nextEntry();
119        }
120        catch (Exception e)
121        {
122          debugException(e);
123    
124          final Throwable cause = e.getCause();
125          if ((cause != null) && (cause instanceof LDAPException))
126          {
127            throw new LDAPPersistException((LDAPException) cause);
128          }
129          else
130          {
131            throw new LDAPPersistException(
132                 ERR_OBJECT_SEARCH_RESULTS_ENTRY_SOURCE_EXCEPTION.get(
133                      getExceptionMessage(e)), e);
134          }
135        }
136    
137        if (entry == null)
138        {
139          return null;
140        }
141        else
142        {
143          return persister.decode(entry);
144        }
145      }
146    
147    
148    
149      /**
150       * Indicates that you wish to stop iterating through search results and will
151       * not be retrieving any additional objects.  This method MUST be called to
152       * avoid leaking resources if you stop iterating through results before the
153       * {@link #next} method returns {@code null} to indicate that there are no
154       * more objects to retrieve.  This method MAY be called after the search has
155       * completed (including being called multiple times) with no adverse effects.
156       */
157      public void close()
158      {
159        entrySource.close();
160      }
161    
162    
163    
164      /**
165       * Retrieves the search result for the search operation, if available.  It
166       * will not be available until the search has completed (as indicated by a
167       * {@code null} return value from the {@link #next} method), and for some use
168       * cases it may never be available.
169       *
170       * @return  The search result for the search operation, or {@code null} if it
171       *          is not available (e.g., because the search has not yet completed).
172       */
173      public SearchResult getSearchResult()
174      {
175        if (entrySource instanceof LDAPEntrySource)
176        {
177          return ((LDAPEntrySource) entrySource).getSearchResult();
178        }
179        else
180        {
181          return null;
182        }
183      }
184    }