001/*
002 * Copyright 2009-2017 UnboundID Corp.
003 * All Rights Reserved.
004 */
005/*
006 * Copyright (C) 2009-2017 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 */
021package com.unboundid.ldap.sdk.persist;
022
023
024
025import java.io.Closeable;
026import java.io.Serializable;
027
028import com.unboundid.ldap.sdk.Entry;
029import com.unboundid.ldap.sdk.EntrySource;
030import com.unboundid.ldap.sdk.LDAPEntrySource;
031import com.unboundid.ldap.sdk.LDAPException;
032import com.unboundid.ldap.sdk.SearchResult;
033import com.unboundid.util.ThreadSafety;
034import com.unboundid.util.ThreadSafetyLevel;
035
036import static com.unboundid.ldap.sdk.persist.PersistMessages.*;
037import static com.unboundid.util.Debug.*;
038import 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)
063public 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}