001    /*
002     * Copyright 2009-2015 UnboundID Corp.
003     * All Rights Reserved.
004     */
005    /*
006     * Copyright (C) 2009-2015 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;
022    
023    
024    
025    import com.unboundid.util.NotExtensible;
026    import com.unboundid.util.ThreadSafety;
027    import com.unboundid.util.ThreadSafetyLevel;
028    
029    
030    
031    /**
032     * This class defines an API that may be implemented by a class that provides
033     * access to a sequence of entries, one entry at a time (e.g., entries read from
034     * an LDIF file, or returned as part of an LDAP search).  It provides a
035     * convenient way to operate on a set of entries without regard for the source
036     * of those entries.  Implementations currently available include the
037     * {@link LDAPEntrySource} class, which can be used to iterate across entries
038     * returned from a directory server in response to a search request, and the
039     * {@link com.unboundid.ldif.LDIFEntrySource} class, which can be used to
040     * iterate across entries in an LDIF file.
041     * <BR><BR>
042     * Note that the {@link #close} method MUST be called if the entry source is to
043     * be discarded before guaranteeing that all entries have been read.  The
044     * {@code close} method may be called after all entries have been read, but it
045     * is not required.  All entry source implementations MUST ensure that all
046     * resources are properly released if the caller has read through all entries,
047     * or if an error occurs that prevents the caller from continuing to read
048     * through the entries (i.e., if {@link #nextEntry} throws an
049     * {@link EntrySourceException} and the
050     * {@link EntrySourceException#mayContinueReading()} method returns
051     * {@code false}).
052     * <BR><BR>
053     * <H2>Example</H2>
054     * The following example demonstrates the process that may be used for iterating
055     * across the entries provided by an entry source:
056     * <PRE>
057     * LDIFReader ldifReader = new LDIFReader(ldifFilePath);
058     * EntrySource entrySource = new LDIFEntrySource(ldifReader);
059     *
060     * int entriesRead = 0;
061     * int exceptionsCaught = 0;
062     * try
063     * {
064     *   while (true)
065     *   {
066     *     try
067     *     {
068     *       Entry entry = entrySource.nextEntry();
069     *       if (entry == null)
070     *       {
071     *         // There are no more entries to be read.
072     *         break;
073     *       }
074     *       else
075     *       {
076     *         // Do something with the entry here.
077     *         entriesRead++;
078     *       }
079     *     }
080     *     catch (EntrySourceException e)
081     *     {
082     *       // Some kind of problem was encountered (e.g., a malformed entry
083     *       // found in an LDIF file, or a referral returned from a directory).
084     *       // See if we can continue reading entries.
085     *       exceptionsCaught++;
086     *       if (! e.mayContinueReading())
087     *       {
088     *         break;
089     *       }
090     *     }
091     *   }
092     * }
093     * finally
094     * {
095     *   entrySource.close();
096     * }
097     * </PRE>
098     */
099    @NotExtensible()
100    @ThreadSafety(level=ThreadSafetyLevel.INTERFACE_NOT_THREADSAFE)
101    public abstract class EntrySource
102    {
103      /**
104       * Retrieves the next entry from the entry source, if there is at least one
105       * remaining entry.  This method may block if no entries are immediately
106       * available.
107       *
108       * @return  The next entry from the entry source, or {@code null} if there are
109       *          no more entries to retrieve..
110       *
111       * @throws  EntrySourceException  If a problem occurs while attempting to read
112       *                                the next entry from the entry source.
113       */
114      public abstract Entry nextEntry()
115             throws EntrySourceException;
116    
117    
118    
119      /**
120       * Indicates that this entry source will no longer be needed and any resources
121       * associated with it may be closed.  This method MUST be called if the entry
122       * source is no longer needed before all entries have been read.  It MAY be
123       * called after all entries have been read with no ill effects, but this is
124       * not necessary as the entry source will have already been closed after all
125       * entries have been read.
126       */
127      public abstract void close();
128    }