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25  
26  package javax.sql.rowset.spi;
27  
28  import javax.sql.*;
29  
30  /**
31   * The synchronization mechanism that provides reader/writer capabilities for
32   * disconnected <code>RowSet</code> objects.
33   * A <code>SyncProvider</code> implementation is a class that extends the
34   * <code>SyncProvider</code> abstract class.
35   * <P>
36   * A <code>SyncProvider</code> implementation is
37   * identified by a unique ID, which is its fully qualified class name.
38   * This name must be registered with the
39   * <code>SyncFactory</code> SPI, thus making the implementation available to
40   * all <code>RowSet</code> implementations.
41   * The factory mechanism in the reference implementation uses this name to instantiate
42   * the implementation, which can then provide a <code>RowSet</code> object with its
43   * reader (a <code>javax.sql.RowSetReader</code> object) and its writer (a
44   * <code>javax.sql.RowSetWriter</code> object).
45   * <P>
46   * The Jdbc <code>RowSet</code> Implementations specification provides two
47   * reference implementations of the <code>SyncProvider</code> abstract class:
48   * <code>RIOptimisticProvider</code> and <code>RIXMLProvider</code>.
49   * The <code>RIOptimisticProvider</code> can set any <code>RowSet</code>
50   * implementation with a <code>RowSetReader</code> object and a
51   * <code>RowSetWriter</code> object.  However, only the <code>RIXMLProvider</code>
52   * implementation can set an <code>XmlReader</code> object and an
53   * <code>XmlWriter</code> object. A <code>WebRowSet</code> object uses the
54   * <code>XmlReader</code> object to read data in XML format to populate itself with that
55   * data.  It uses the <code>XmlWriter</code> object to write itself to a stream or
56   * <code>java.io.Writer</code> object in XML format.
57   *
58   * <h3>1.0 Naming Convention for Implementations</h3>
59   * As a guide  to naming <code>SyncProvider</code>
60   * implementations, the following should be noted:
61   * <UL>
62   * <li>The name for a <code>SyncProvider</code> implementation
63   * is its fully qualified class name.
64   * <li>It is recommended that vendors supply a
65   * <code>SyncProvider</code> implementation in a package named <code>providers</code>.
66   * </UL>
67   * <p>
68   * For instance, if a vendor named Fred, Inc. offered a
69   * <code>SyncProvider</code> implementation, you could have the following:
70   * <PRE>
71   *     Vendor name:  Fred, Inc.
72   *     Domain name of vendor:  com.fred
73   *     Package name:  com.fred.providers
74   *     SyncProvider implementation class name:  HighAvailabilityProvider
75   *
76   *     Fully qualified class name of SyncProvider implementation:
77   *                        com.fred.providers.HighAvailabilityProvider
78   * </PRE>
79   * <P>
80   * The following line of code uses the fully qualified name to register
81   * this implementation with the <code>SyncFactory</code> static instance.
82   * <PRE>
83   *     SyncFactory.registerProvider(
84   *                          "com.fred.providers.HighAvailabilityProvider");
85   * </PRE>
86   * <P>
87   * The default <code>SyncProvider</code> object provided with the reference
88   * implementation uses the following name:
89   * <pre>
90   *     com.sun.rowset.providers.RIOptimisticProvider
91   * </pre>
92   * <p>
93   * A vendor can register a <code>SyncProvider</code> implementation class name
94   * with Oracle Corporation by sending email to jdbc@sun.com.
95   * Oracle will maintain a database listing the
96   * available <code>SyncProvider</code> implementations for use with compliant
97   * <code>RowSet</code> implementations.  This database will be similar to the
98   * one already maintained to list available JDBC drivers.
99   * <P>
100  * Vendors should refer to the reference implementation synchronization
101  * providers for additional guidance on how to implement a new
102  * <code>SyncProvider</code> implementation.
103  *
104  * <h3>2.0 How a <code>RowSet</code> Object Gets Its Provider</h3>
105  *
106  * A disconnected <code>Rowset</code> object may get access to a
107  * <code>SyncProvider</code> object in one of the following two ways:
108  * <UL>
109  *  <LI>Using a constructor<BR>
110  *      <PRE>
111  *       CachedRowSet crs = new CachedRowSet(
112  *                  "com.fred.providers.HighAvailabilitySyncProvider");
113  *      </PRE>
114  *  <LI>Using the <code>setSyncProvider</code> method
115  *      <PRE>
116  *       CachedRowSet crs = new CachedRowSet();
117  *       crs.setSyncProvider("com.fred.providers.HighAvailabilitySyncProvider");
118  *      </PRE>
119 
120  * </UL>
121  * <p>
122  * By default, the reference implementations of the <code>RowSet</code> synchronization
123  * providers are always available to the Java platform.
124  * If no other pluggable synchronization providers have been correctly
125  * registered, the <code>SyncFactory</code> will automatically generate
126  * an instance of the default <code>SyncProvider</code> reference implementation.
127  * Thus, in the preceding code fragment, if no implementation named
128  * <code>com.fred.providers.HighAvailabilitySyncProvider</code> has been
129  * registered with the <code>SyncFactory</code> instance, <i>crs</i> will be
130  * assigned the default provider in the reference implementation, which is
131  * <code>com.sun.rowset.providers.RIOptimisticProvider</code>.
132  *
133  * <h3>3.0 Violations and Synchronization Issues</h3>
134  * If an update between a disconnected <code>RowSet</code> object
135  * and a data source violates
136  * the original query or the underlying data source constraints, this will
137  * result in undefined behavior for all disconnected <code>RowSet</code> implementations
138  * and their designated <code>SyncProvider</code> implementations.
139  * Not defining the behavior when such violations occur offers greater flexibility
140  * for a <code>SyncProvider</code>
141  * implementation to determine its own best course of action.
142  * <p>
143  * A <code>SyncProvider</code> implementation
144  * may choose to implement a specific handler to
145  * handle a subset of query violations.
146  * However if an original query violation or a more general data source constraint
147  * violation is not handled by the <code>SyncProvider</code> implementation,
148  * all <code>SyncProvider</code>
149  * objects must throw a <code>SyncProviderException</code>.
150  *
151  * <h3>4.0 Updatable SQL VIEWs</h3>
152  * It is possible for any disconnected or connected <code>RowSet</code> object to be populated
153  * from an SQL query that is formulated originally from an SQL <code>VIEW</code>.
154  * While in many cases it is possible for an update to be performed to an
155  * underlying view, such an update requires additional metadata, which may vary.
156  * The <code>SyncProvider</code> class provides two constants to indicate whether
157  * an implementation supports updating an SQL <code>VIEW</code>.
158  * <ul>
159  * <li><code><b>NONUPDATABLE_VIEW_SYNC</b></code> - Indicates that a <code>SyncProvider</code>
160  * implementation does not support synchronization with an SQL <code>VIEW</code> as the
161  * underlying source of data for the <code>RowSet</code> object.
162  * <li><code><b>UPDATABLE_VIEW_SYNC</b></code> - Indicates that a
163  * <code>SyncProvider</code> implementation
164  * supports synchronization with an SQL <code>VIEW</code> as the underlying source
165  * of data.
166  * </ul>
167  * <P>
168  * The default is for a <code>RowSet</code> object not to be updatable if it was
169  * populated with data from an SQL <code>VIEW</code>.
170  *
171  * <h3>5.0 <code>SyncProvider</code> Constants</h3>
172  * The <code>SyncProvider</code> class provides three sets of constants that
173  * are used as return values or parameters for <code>SyncProvider</code> methods.
174  * <code>SyncProvider</code> objects may be implemented to perform synchronization
175  * between a <code>RowSet</code> object and its underlying data source with varying
176  * degrees of of care. The first group of constants indicate how synchronization
177  * is handled. For example, <code>GRADE_NONE</code> indicates that a
178  * <code>SyncProvider</code> object will not take any care to see what data is
179  * valid and will simply write the <code>RowSet</code> data to the data source.
180  * <code>GRADE_MODIFIED_AT_COMMIT</code> indicates that the provider will check
181  * only modified data for validity.  Other grades check all data for validity
182  * or set locks when data is modified or loaded.
183  * <OL>
184  *  <LI>Constants to indicate the synchronization grade of a
185  *     <code>SyncProvider</code> object
186  *   <UL>
187  *    <LI>SyncProvider.GRADE_NONE
188  *    <LI>SyncProvider.GRADE_MODIFIED_AT_COMMIT
189  *    <LI>SyncProvider.GRADE_CHECK_ALL_AT_COMMIT
190  *    <LI>SyncProvider.GRADE_LOCK_WHEN_MODIFIED
191  *    <LI>SyncProvider.GRADE_LOCK_WHEN_LOADED
192  *   </UL>
193  *  <LI>Constants to indicate what locks are set on the data source
194  *   <UL>
195  *     <LI>SyncProvider.DATASOURCE_NO_LOCK
196  *     <LI>SyncProvider.DATASOURCE_ROW_LOCK
197  *     <LI>SyncProvider.DATASOURCE_TABLE_LOCK
198  *     <LI>SyncProvider.DATASOURCE_DB_LOCK
199  *   </UL>
200  *  <LI>Constants to indicate whether a <code>SyncProvider</code> object can
201  *       perform updates to an SQL <code>VIEW</code> <BR>
202  *       These constants are explained in the preceding section (4.0).
203  *   <UL>
204  *     <LI>SyncProvider.UPDATABLE_VIEW_SYNC
205  *     <LI>SyncProvider.NONUPDATABLE_VIEW_SYNC
206  *   </UL>
207  * </OL>
208  *
209  * @author Jonathan Bruce
210  * @see javax.sql.rowset.spi.SyncFactory
211  * @see javax.sql.rowset.spi.SyncFactoryException
212  */
213 public abstract class SyncProvider {
214 
215    /**
216     * Creates a default <code>SyncProvider</code> object.
217     */
218     public SyncProvider() {
219     }
220 
221     /**
222      * Returns the unique identifier for this <code>SyncProvider</code> object.
223      *
224      * @return a <code>String</code> object with the fully qualified class name of
225      *         this <code>SyncProvider</code> object
226      */
227     public abstract String getProviderID();
228 
229     /**
230      * Returns a <code>javax.sql.RowSetReader</code> object, which can be used to
231      * populate a <code>RowSet</code> object with data.
232      *
233      * @return a <code>javax.sql.RowSetReader</code> object
234      */
235     public abstract RowSetReader getRowSetReader();
236 
237     /**
238      * Returns a <code>javax.sql.RowSetWriter</code> object, which can be
239      * used to write a <code>RowSet</code> object's data back to the
240      * underlying data source.
241      *
242      * @return a <code>javax.sql.RowSetWriter</code> object
243      */
244     public abstract RowSetWriter getRowSetWriter();
245 
246     /**
247      * Returns a constant indicating the
248      * grade of synchronization a <code>RowSet</code> object can expect from
249      * this <code>SyncProvider</code> object.
250      *
251      * @return an int that is one of the following constants:
252      *           SyncProvider.GRADE_NONE,
253      *           SyncProvider.GRADE_CHECK_MODIFIED_AT_COMMIT,
254      *           SyncProvider.GRADE_CHECK_ALL_AT_COMMIT,
255      *           SyncProvider.GRADE_LOCK_WHEN_MODIFIED,
256      *           SyncProvider.GRADE_LOCK_WHEN_LOADED
257      */
258     public abstract int getProviderGrade();
259 
260 
261     /**
262      * Sets a lock on the underlying data source at the level indicated by
263      * <i>datasource_lock</i>. This should cause the
264      * <code>SyncProvider</code> to adjust its behavior by increasing or
265      * decreasing the level of optimism it provides for a successful
266      * synchronization.
267      *
268      * @param datasource_lock one of the following constants indicating the severity
269      *           level of data source lock required:
270      * <pre>
271      *           SyncProvider.DATASOURCE_NO_LOCK,
272      *           SyncProvider.DATASOURCE_ROW_LOCK,
273      *           SyncProvider.DATASOURCE_TABLE_LOCK,
274      *           SyncProvider.DATASOURCE_DB_LOCK,
275      * </pre>
276      * @throws SyncProviderException if an unsupported data source locking level
277      *           is set.
278      * @see #getDataSourceLock
279      */
280     public abstract void setDataSourceLock(int datasource_lock)
281         throws SyncProviderException;
282 
283     /**
284      * Returns the current data source lock severity level active in this
285      * <code>SyncProvider</code> implementation.
286      *
287      * @return a constant indicating the current level of data source lock
288      *        active in this <code>SyncProvider</code> object;
289      *         one of the following:
290      * <pre>
291      *           SyncProvider.DATASOURCE_NO_LOCK,
292      *           SyncProvider.DATASOURCE_ROW_LOCK,
293      *           SyncProvider.DATASOURCE_TABLE_LOCK,
294      *           SyncProvider.DATASOURCE_DB_LOCK
295      * </pre>
296      * @throws SyncProviderException if an error occurs determining the data
297      *        source locking level.
298      * @see #setDataSourceLock
299 
300      */
301     public abstract int getDataSourceLock()
302         throws SyncProviderException;
303 
304     /**
305      * Returns whether this <code>SyncProvider</code> implementation
306      * can perform synchronization between a <code>RowSet</code> object
307      * and the SQL <code>VIEW</code> in the data source from which
308      * the <code>RowSet</code> object got its data.
309      *
310      * @return an <code>int</code> saying whether this <code>SyncProvider</code>
311      *         object supports updating an SQL <code>VIEW</code>; one of the
312      *         following:
313      *            SyncProvider.UPDATABLE_VIEW_SYNC,
314      *            SyncProvider.NONUPDATABLE_VIEW_SYNC
315      */
316     public abstract int supportsUpdatableView();
317 
318     /**
319      * Returns the release version of this <code>SyncProvider</code> instance.
320      *
321      * @return a <code>String</code> detailing the release version of the
322      *     <code>SyncProvider</code> implementation
323      */
324     public abstract String getVersion();
325 
326     /**
327      * Returns the vendor name of this <code>SyncProvider</code> instance
328      *
329      * @return a <code>String</code> detailing the vendor name of this
330      *     <code>SyncProvider</code> implementation
331      */
332     public abstract String getVendor();
333 
334     /*
335      * Standard description of synchronization grades that a SyncProvider
336      * could provide.
337      */
338 
339     /**
340      * Indicates that no synchronization with the originating data source is
341      * provided. A <code>SyncProvider</code>
342      * implementation returning this grade will simply attempt to write
343      * updates in the <code>RowSet</code> object to the underlying data
344      * source without checking the validity of any data.
345      *
346      */
347     public static final int GRADE_NONE = 1;
348 
349     /**
350      * Indicates a low level optimistic synchronization grade with
351      * respect to the originating data source.
352      *
353      * A <code>SyncProvider</code> implementation
354      * returning this grade will check only rows that have changed.
355      *
356      */
357     public static final int GRADE_CHECK_MODIFIED_AT_COMMIT = 2;
358 
359     /**
360      * Indicates a high level optimistic synchronization grade with
361      * respect to the originating data source.
362      *
363      * A <code>SyncProvider</code> implementation
364      * returning this grade will check all rows, including rows that have not
365      * changed.
366      */
367     public static final int GRADE_CHECK_ALL_AT_COMMIT = 3;
368 
369     /**
370      * Indicates a pessimistic synchronization grade with
371      * respect to the originating data source.
372      *
373      * A <code>SyncProvider</code>
374      * implementation returning this grade will lock the row in the originating
375      * data source.
376      */
377     public static final int GRADE_LOCK_WHEN_MODIFIED = 4;
378 
379     /**
380      * Indicates the most pessimistic synchronization grade with
381      * respect to the originating
382      * data source. A <code>SyncProvider</code>
383      * implementation returning this grade will lock the entire view and/or
384      * table affected by the original statement used to populate a
385      * <code>RowSet</code> object.
386      */
387     public static final int GRADE_LOCK_WHEN_LOADED = 5;
388 
389     /**
390      * Indicates that no locks remain on the originating data source. This is the default
391      * lock setting for all <code>SyncProvider</code> implementations unless
392      * otherwise directed by a <code>RowSet</code> object.
393      */
394     public static final int DATASOURCE_NO_LOCK = 1;
395 
396     /**
397      * Indicates that a lock is placed on the rows that are touched by the original
398      * SQL statement used to populate the <code>RowSet</code> object
399      * that is using this <code>SyncProvider</code> object.
400      */
401     public static final int DATASOURCE_ROW_LOCK = 2;
402 
403     /**
404      * Indicates that a lock is placed on all tables that are touched by the original
405      * SQL statement used to populate the <code>RowSet</code> object
406      * that is using this <code>SyncProvider</code> object.
407      */
408     public static final int DATASOURCE_TABLE_LOCK = 3;
409 
410     /**
411      * Indicates that a lock is placed on the entire data source that is the source of
412      * data for the <code>RowSet</code> object
413      * that is using this <code>SyncProvider</code> object.
414      */
415     public static final int DATASOURCE_DB_LOCK = 4;
416 
417     /**
418      * Indicates that a <code>SyncProvider</code> implementation
419      * supports synchronization between a <code>RowSet</code> object and
420      * the SQL <code>VIEW</code> used to populate it.
421      */
422     public static final int UPDATABLE_VIEW_SYNC = 5;
423 
424     /**
425      * Indicates that a <code>SyncProvider</code> implementation
426      * does <B>not</B> support synchronization between a <code>RowSet</code>
427      * object and the SQL <code>VIEW</code> used to populate it.
428      */
429     public static final int NONUPDATABLE_VIEW_SYNC = 6;
430 }