001    /*
002     * Copyright 2007-2016 UnboundID Corp.
003     * All Rights Reserved.
004     */
005    /*
006     * Copyright (C) 2008-2016 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.controls;
022    
023    
024    
025    import com.unboundid.asn1.ASN1Element;
026    import com.unboundid.asn1.ASN1Exception;
027    import com.unboundid.asn1.ASN1Integer;
028    import com.unboundid.asn1.ASN1OctetString;
029    import com.unboundid.asn1.ASN1Sequence;
030    import com.unboundid.ldap.sdk.Control;
031    import com.unboundid.ldap.sdk.DecodeableControl;
032    import com.unboundid.ldap.sdk.LDAPException;
033    import com.unboundid.ldap.sdk.ResultCode;
034    import com.unboundid.ldap.sdk.SearchResult;
035    import com.unboundid.util.NotMutable;
036    import com.unboundid.util.ThreadSafety;
037    import com.unboundid.util.ThreadSafetyLevel;
038    
039    import static com.unboundid.ldap.sdk.controls.ControlMessages.*;
040    import static com.unboundid.util.Debug.*;
041    
042    
043    
044    /**
045     * This class provides an implementation of the simple paged results control as
046     * defined in <A HREF="http://www.ietf.org/rfc/rfc2696.txt">RFC 2696</A>.  It
047     * allows the client to iterate through a potentially large set of search
048     * results in subsets of a specified number of entries (i.e., "pages").
049     * <BR><BR>
050     * The same control encoding is used for both the request control sent by
051     * clients and the response control returned by the server.  It may contain
052     * two elements:
053     * <UL>
054     *   <LI>Size -- In a request control, this provides the requested page size,
055     *       which is the maximum number of entries that the server should return
056     *       in the next iteration of the search.  In a response control, it is an
057     *       estimate of the total number of entries that match the search
058     *       criteria.</LI>
059     *   <LI>Cookie -- A token which is used by the server to keep track of its
060     *       position in the set of search results.  The first request sent by the
061     *       client should not include a cookie, and the last response sent by the
062     *       server should not include a cookie.  For all other intermediate search
063     *       requests and responses,  the server will include a cookie value in its
064     *       response that the client should include in its next request.</LI>
065     * </UL>
066     * When the client wishes to use the paged results control, the first search
067     * request should include a version of the paged results request control that
068     * was created with a requested page size but no cookie.  The corresponding
069     * response from the server will include a version of the paged results control
070     * that may include an estimate of the total number of matching entries, and
071     * may also include a cookie.  The client should include this cookie in the
072     * next request (with the same set of search criteria) to retrieve the next page
073     * of results.  This process should continue until the response control returned
074     * by the server does not include a cookie, which indicates that the end of the
075     * result set has been reached.
076     * <BR><BR>
077     * Note that the simple paged results control is similar to the
078     * {@link VirtualListViewRequestControl} in that both allow the client to
079     * request that only a portion of the result set be returned at any one time.
080     * However, there are significant differences between them, including:
081     * <UL>
082     *   <LI>In order to use the virtual list view request control, it is also
083     *       necessary to use the {@link ServerSideSortRequestControl} to ensure
084     *       that the entries are sorted.  This is not a requirement for the
085     *       simple paged results control.</LI>
086     *   <LI>The simple paged results control may only be used to iterate
087     *       sequentially through the set of search results.  The virtual list view
088     *       control can retrieve pages out of order, can retrieve overlapping
089     *       pages, and can re-request pages that it had already retrieved.</LI>
090     * </UL>
091     * <H2>Example</H2>
092     * The following example demonstrates the use of the simple paged results
093     * control.  It will iterate through all users, retrieving up to 10 entries at a
094     * time:
095     * <PRE>
096     * // Perform a search to retrieve all users in the server, but only retrieving
097     * // ten at a time.
098     * int numSearches = 0;
099     * int totalEntriesReturned = 0;
100     * SearchRequest searchRequest = new SearchRequest("dc=example,dc=com",
101     *      SearchScope.SUB, Filter.createEqualityFilter("objectClass", "person"));
102     * ASN1OctetString resumeCookie = null;
103     * while (true)
104     * {
105     *   searchRequest.setControls(
106     *        new SimplePagedResultsControl(10, resumeCookie));
107     *   SearchResult searchResult = connection.search(searchRequest);
108     *   numSearches++;
109     *   totalEntriesReturned += searchResult.getEntryCount();
110     *   for (SearchResultEntry e : searchResult.getSearchEntries())
111     *   {
112     *     // Do something with each entry...
113     *   }
114     *
115     *   LDAPTestUtils.assertHasControl(searchResult,
116     *        SimplePagedResultsControl.PAGED_RESULTS_OID);
117     *   SimplePagedResultsControl responseControl =
118     *        SimplePagedResultsControl.get(searchResult);
119     *   if (responseControl.moreResultsToReturn())
120     *   {
121     *     // The resume cookie can be included in the simple paged results
122     *     // control included in the next search to get the next page of results.
123     *     resumeCookie = responseControl.getCookie();
124     *   }
125     *   else
126     *   {
127     *     break;
128     *   }
129     * }
130     * </PRE>
131     */
132    @NotMutable()
133    @ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
134    public final class SimplePagedResultsControl
135           extends Control
136           implements DecodeableControl
137    {
138      /**
139       * The OID (1.2.840.113556.1.4.319) for the paged results control.
140       */
141      public static final String PAGED_RESULTS_OID = "1.2.840.113556.1.4.319";
142    
143    
144    
145      /**
146       * The serial version UID for this serializable class.
147       */
148      private static final long serialVersionUID = 2186787148024999291L;
149    
150    
151    
152      // The encoded cookie returned from the server (for a response control) or
153      // that should be included in the next request to the server (for a request
154      // control).
155      private final ASN1OctetString cookie;
156    
157      // The maximum requested page size (for a request control), or the estimated
158      // total result set size (for a response control).
159      private final int size;
160    
161    
162    
163      /**
164       * Creates a new empty control instance that is intended to be used only for
165       * decoding controls via the {@code DecodeableControl} interface.
166       */
167      SimplePagedResultsControl()
168      {
169        size   = 0;
170        cookie = new ASN1OctetString();
171      }
172    
173    
174    
175      /**
176       * Creates a new paged results control with the specified page size.  This
177       * version of the constructor should only be used when creating the first
178       * search as part of the set of paged results.  Subsequent searches to
179       * retrieve additional pages should use the response control returned by the
180       * server in their next request, until the response control returned by the
181       * server does not include a cookie.
182       *
183       * @param  pageSize  The maximum number of entries that the server should
184       *                   return in the first page.
185       */
186      public SimplePagedResultsControl(final int pageSize)
187      {
188        super(PAGED_RESULTS_OID, false, encodeValue(pageSize, null));
189    
190        size   = pageSize;
191        cookie = new ASN1OctetString();
192      }
193    
194    
195    
196      /**
197       * Creates a new paged results control with the specified page size.  This
198       * version of the constructor should only be used when creating the first
199       * search as part of the set of paged results.  Subsequent searches to
200       * retrieve additional pages should use the response control returned by the
201       * server in their next request, until the response control returned by the
202       * server does not include a cookie.
203       *
204       * @param  pageSize    The maximum number of entries that the server should
205       *                     return in the first page.
206       * @param  isCritical  Indicates whether this control should be marked
207       *                     critical.
208       */
209      public SimplePagedResultsControl(final int pageSize, final boolean isCritical)
210      {
211        super(PAGED_RESULTS_OID, isCritical, encodeValue(pageSize, null));
212    
213        size   = pageSize;
214        cookie = new ASN1OctetString();
215      }
216    
217    
218    
219      /**
220       * Creates a new paged results control with the specified page size and the
221       * provided cookie.  This version of the constructor should be used to
222       * continue iterating through an existing set of results, but potentially
223       * using a different page size.
224       *
225       * @param  pageSize  The maximum number of entries that the server should
226       *                   return in the next page of the results.
227       * @param  cookie    The cookie provided by the server after returning the
228       *                   previous page of results, or {@code null} if this request
229       *                   will retrieve the first page of results.
230       */
231      public SimplePagedResultsControl(final int pageSize,
232                                       final ASN1OctetString cookie)
233      {
234        super(PAGED_RESULTS_OID, false, encodeValue(pageSize, cookie));
235    
236        size = pageSize;
237    
238        if (cookie == null)
239        {
240          this.cookie = new ASN1OctetString();
241        }
242        else
243        {
244          this.cookie = cookie;
245        }
246      }
247    
248    
249    
250      /**
251       * Creates a new paged results control with the specified page size and the
252       * provided cookie.  This version of the constructor should be used to
253       * continue iterating through an existing set of results, but potentially
254       * using a different page size.
255       *
256       * @param  pageSize    The maximum number of entries that the server should
257       *                     return in the first page.
258       * @param  cookie      The cookie provided by the server after returning the
259       *                     previous page of results, or {@code null} if this
260       *                     request will retrieve the first page of results.
261       * @param  isCritical  Indicates whether this control should be marked
262       *                     critical.
263       */
264      public SimplePagedResultsControl(final int pageSize,
265                                       final ASN1OctetString cookie,
266                                       final boolean isCritical)
267      {
268        super(PAGED_RESULTS_OID, isCritical, encodeValue(pageSize, cookie));
269    
270        size = pageSize;
271    
272        if (cookie == null)
273        {
274          this.cookie = new ASN1OctetString();
275        }
276        else
277        {
278          this.cookie = cookie;
279        }
280      }
281    
282    
283    
284      /**
285       * Creates a new paged results control from the control with the provided set
286       * of information.  This should be used to decode the paged results response
287       * control returned by the server with a page of results.
288       *
289       * @param  oid         The OID for the control.
290       * @param  isCritical  Indicates whether the control should be marked
291       *                     critical.
292       * @param  value       The encoded value for the control.  This may be
293       *                     {@code null} if no value was provided.
294       *
295       * @throws  LDAPException  If the provided control cannot be decoded as a
296       *                         simple paged results control.
297       */
298      public SimplePagedResultsControl(final String oid, final boolean isCritical,
299                                       final ASN1OctetString value)
300             throws LDAPException
301      {
302        super(oid, isCritical, value);
303    
304        if (value == null)
305        {
306          throw new LDAPException(ResultCode.DECODING_ERROR,
307                                  ERR_PAGED_RESULTS_NO_VALUE.get());
308        }
309    
310        final ASN1Sequence valueSequence;
311        try
312        {
313          final ASN1Element valueElement = ASN1Element.decode(value.getValue());
314          valueSequence = ASN1Sequence.decodeAsSequence(valueElement);
315        }
316        catch (final ASN1Exception ae)
317        {
318          debugException(ae);
319          throw new LDAPException(ResultCode.DECODING_ERROR,
320                                  ERR_PAGED_RESULTS_VALUE_NOT_SEQUENCE.get(ae), ae);
321        }
322    
323        final ASN1Element[] valueElements = valueSequence.elements();
324        if (valueElements.length != 2)
325        {
326          throw new LDAPException(ResultCode.DECODING_ERROR,
327                                  ERR_PAGED_RESULTS_INVALID_ELEMENT_COUNT.get(
328                                       valueElements.length));
329        }
330    
331        try
332        {
333          size = ASN1Integer.decodeAsInteger(valueElements[0]).intValue();
334        }
335        catch (final ASN1Exception ae)
336        {
337          debugException(ae);
338          throw new LDAPException(ResultCode.DECODING_ERROR,
339                                  ERR_PAGED_RESULTS_FIRST_NOT_INTEGER.get(ae), ae);
340        }
341    
342        cookie = ASN1OctetString.decodeAsOctetString(valueElements[1]);
343      }
344    
345    
346    
347      /**
348       * {@inheritDoc}
349       */
350      public SimplePagedResultsControl
351                  decodeControl(final String oid, final boolean isCritical,
352                                final ASN1OctetString value)
353             throws LDAPException
354      {
355        return new SimplePagedResultsControl(oid, isCritical, value);
356      }
357    
358    
359    
360      /**
361       * Extracts a simple paged results response control from the provided result.
362       *
363       * @param  result  The result from which to retrieve the simple paged results
364       *                 response control.
365       *
366       * @return  The simple paged results response control contained in the
367       *          provided result, or {@code null} if the result did not contain a
368       *          simple paged results response control.
369       *
370       * @throws  LDAPException  If a problem is encountered while attempting to
371       *                         decode the simple paged results response control
372       *                         contained in the provided result.
373       */
374      public static SimplePagedResultsControl get(final SearchResult result)
375             throws LDAPException
376      {
377        final Control c = result.getResponseControl(PAGED_RESULTS_OID);
378        if (c == null)
379        {
380          return null;
381        }
382    
383        if (c instanceof SimplePagedResultsControl)
384        {
385          return (SimplePagedResultsControl) c;
386        }
387        else
388        {
389          return new SimplePagedResultsControl(c.getOID(), c.isCritical(),
390               c.getValue());
391        }
392      }
393    
394    
395    
396      /**
397       * Encodes the provided information into an octet string that can be used as
398       * the value for this control.
399       *
400       * @param  pageSize  The maximum number of entries that the server should
401       *                   return in the next page of the results.
402       * @param  cookie    The cookie provided by the server after returning the
403       *                   previous page of results, or {@code null} if this request
404       *                   will retrieve the first page of results.
405       *
406       * @return  An ASN.1 octet string that can be used as the value for this
407       *          control.
408       */
409      private static ASN1OctetString encodeValue(final int pageSize,
410                                                 final ASN1OctetString cookie)
411      {
412        final ASN1Element[] valueElements;
413        if (cookie == null)
414        {
415          valueElements = new ASN1Element[]
416          {
417            new ASN1Integer(pageSize),
418            new ASN1OctetString()
419          };
420        }
421        else
422        {
423          valueElements = new ASN1Element[]
424          {
425            new ASN1Integer(pageSize),
426            cookie
427          };
428        }
429    
430        return new ASN1OctetString(new ASN1Sequence(valueElements).encode());
431      }
432    
433    
434    
435      /**
436       * Retrieves the size for this paged results control.  For a request control,
437       * it may be used to specify the number of entries that should be included in
438       * the next page of results.  For a response control, it may be used to
439       * specify the estimated number of entries in the complete result set.
440       *
441       * @return  The size for this paged results control.
442       */
443      public int getSize()
444      {
445        return size;
446      }
447    
448    
449    
450      /**
451       * Retrieves the cookie for this control, which may be used in a subsequent
452       * request to resume reading entries from the next page of results.  The
453       * value should have a length of zero when used to retrieve the first page of
454       * results for a given search, and also in the response from the server when
455       * there are no more entries to send.  It should be non-empty for all other
456       * conditions.
457       *
458       * @return  The cookie for this control, or {@code null} if there is none.
459       */
460      public ASN1OctetString getCookie()
461      {
462        return cookie;
463      }
464    
465    
466    
467      /**
468       * Indicates whether there are more results to return as part of this search.
469       *
470       * @return  {@code true} if there are more results to return, or
471       *          {@code false} if not.
472       */
473      public boolean moreResultsToReturn()
474      {
475        return (cookie.getValue().length > 0);
476      }
477    
478    
479    
480      /**
481       * {@inheritDoc}
482       */
483      @Override()
484      public String getControlName()
485      {
486        return INFO_CONTROL_NAME_PAGED_RESULTS.get();
487      }
488    
489    
490    
491      /**
492       * {@inheritDoc}
493       */
494      @Override()
495      public void toString(final StringBuilder buffer)
496      {
497        buffer.append("SimplePagedResultsControl(pageSize=");
498        buffer.append(size);
499        buffer.append(", isCritical=");
500        buffer.append(isCritical());
501        buffer.append(')');
502      }
503    }