1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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15 * accompanied this code).
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24 */
25
26 package javax.sql.rowset;
27
28 import java.sql.SQLException;
29
30 /**
31 * <h2>1.0 Background</h2>
32 * The <code>Joinable</code> interface provides the methods for getting and
33 * setting a match column, which is the basis for forming the SQL <code>JOIN</code>
34 * formed by adding <code>RowSet</code> objects to a <code>JoinRowSet</code>
35 * object.
36 * <P>
37 * Any standard <code>RowSet</code> implementation <b>may</b> implement
38 * the <code>Joinable</code> interface in order to be
39 * added to a <code>JoinRowSet</code> object. Implementing this interface gives
40 * a <code>RowSet</code> object the ability to use <code>Joinable</code> methods,
41 * which set, retrieve, and get information about match columns. An
42 * application may add a
43 * <code>RowSet</code> object that has not implemented the <code>Joinable</code>
44 * interface to a <code>JoinRowSet</code> object, but to do so it must use one
45 * of the <code>JoinRowSet.addRowSet</code> methods that takes both a
46 * <code>RowSet</code> object and a match column or an array of <code>RowSet</code>
47 * objects and an array of match columns.
48 * <P>
49 * To get access to the methods in the <code>Joinable</code> interface, a
50 * <code>RowSet</code> object implements at least one of the
51 * five standard <code>RowSet</code> interfaces and also implements the
52 * <code>Joinable</code> interface. In addition, most <code>RowSet</code>
53 * objects extend the <code>BaseRowSet</code> class. For example:
54 * <pre>
55 * class MyRowSetImpl extends BaseRowSet implements CachedRowSet, Joinable {
56 * :
57 * :
58 * }
59 * </pre>
60 *
61 * <h2>2.0 Usage Guidelines</h2>
62 * <P>
63 * The methods in the <code>Joinable</code> interface allow a <code>RowSet</code> object
64 * to set a match column, retrieve a match column, or unset a match column, which is
65 * the column upon which an SQL <code>JOIN</code> can be based.
66 * An instance of a class that implements these methods can be added to a
67 * <code>JoinRowSet</code> object to allow an SQL <code>JOIN</code> relationship to
68 * be established.
69 *
70 * <pre>
71 * CachedRowSet crs = new MyRowSetImpl();
72 * crs.populate((ResultSet)rs);
73 * (Joinable)crs.setMatchColumnIndex(1);
74 *
75 * JoinRowSet jrs = new JoinRowSetImpl();
76 * jrs.addRowSet(crs);
77 * </pre>
78 * In the previous example, <i>crs</i> is a <code>CachedRowSet</code> object that
79 * has implemented the <code>Joinable</code> interface. In the following example,
80 * <i>crs2</i> has not, so it must supply the match column as an argument to the
81 * <code>addRowSet</code> method. This example assumes that column 1 is the match
82 * column.
83 * <PRE>
84 * CachedRowSet crs2 = new MyRowSetImpl();
85 * crs2.populate((ResultSet)rs);
86 *
87 * JoinRowSet jrs2 = new JoinRowSetImpl();
88 * jrs2.addRowSet(crs2, 1);
89 * </PRE>
90 * <p>
91 * The <code>JoinRowSet</code> interface makes it possible to get data from one or
92 * more <code>RowSet</code> objects consolidated into one table without having to incur
93 * the expense of creating a connection to a database. It is therefore ideally suited
94 * for use by disconnected <code>RowSet</code> objects. Nevertheless, any
95 * <code>RowSet</code> object <b>may</b> implement this interface
96 * regardless of whether it is connected or disconnected. Note that a
97 * <code>JdbcRowSet</code> object, being always connected to its data source, can
98 * become part of an SQL <code>JOIN</code> directly without having to become part
99 * of a <code>JoinRowSet</code> object.
100 *
101 * <h2>3.0 Managing Multiple Match Columns</h2>
102 * The index array passed into the <code>setMatchColumn</code> methods indicates
103 * how many match columns are being set (the length of the array) in addition to
104 * which columns will be used for the match. For example:
105 * <pre>
106 * int[] i = {1, 2, 4, 7}; // indicates four match columns, with column
107 * // indexes 1, 2, 4, 7 participating in the JOIN.
108 * Joinable.setMatchColumn(i);
109 * </pre>
110 * Subsequent match columns may be added as follows to a different <code>Joinable</code>
111 * object (a <code>RowSet</code> object that has implemented the <code>Joinable</code>
112 * interface).
113 * <pre>
114 * int[] w = {3, 2, 5, 3};
115 * Joinable2.setMatchColumn(w);
116 * </pre>
117 * When an application adds two or more <code>RowSet</code> objects to a
118 * <code>JoinRowSet</code> object, the order of the indexes in the array is
119 * particularly important. Each index of
120 * the array maps directly to the corresponding index of the previously added
121 * <code>RowSet</code> object. If overlap or underlap occurs, the match column
122 * data is maintained in the event an additional <code>Joinable</code> RowSet is
123 * added and needs to relate to the match column data. Therefore, applications
124 * can set multiple match columns in any order, but
125 * this order has a direct effect on the outcome of the <code>SQL</code> JOIN.
126 * <p>
127 * This assertion applies in exactly the same manner when column names are used
128 * rather than column indexes to indicate match columns.
129 *
130 * @see JoinRowSet
131 * @author Jonathan Bruce
132 * @since 1.5
133 */
134 public interface Joinable {
135
136 /**
137 * Sets the designated column as the match column for this <code>RowSet</code>
138 * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
139 * object based on the match column.
140 * <p>
141 * Sub-interfaces such as the <code>CachedRowSet</code>
142 * interface define the method <code>CachedRowSet.setKeyColumns</code>, which allows
143 * primary key semantics to be enforced on specific columns.
144 * Implementations of the <code>setMatchColumn(int columnIdx)</code> method
145 * should ensure that the constraints on the key columns are maintained when
146 * a <code>CachedRowSet</code> object sets a primary key column as a match column.
147 *
148 * @param columnIdx an <code>int</code> identifying the index of the column to be
149 * set as the match column
150 * @throws SQLException if an invalid column index is set
151 * @see #setMatchColumn(int[])
152 * @see #unsetMatchColumn(int)
153 *
154 */
155 public void setMatchColumn(int columnIdx) throws SQLException;
156
157 /**
158 * Sets the designated columns as the match column for this <code>RowSet</code>
159 * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
160 * object based on the match column.
161 *
162 * @param columnIdxes an array of <code>int</code> identifying the indexes of the
163 * columns to be set as the match columns
164 * @throws SQLException if an invalid column index is set
165 * @see #setMatchColumn(int[])
166 * @see #unsetMatchColumn(int[])
167 */
168 public void setMatchColumn(int[] columnIdxes) throws SQLException;
169
170 /**
171 * Sets the designated column as the match column for this <code>RowSet</code>
172 * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
173 * object based on the match column.
174 * <p>
175 * Subinterfaces such as the <code>CachedRowSet</code> interface define
176 * the method <code>CachedRowSet.setKeyColumns</code>, which allows
177 * primary key semantics to be enforced on specific columns.
178 * Implementations of the <code>setMatchColumn(String columnIdx)</code> method
179 * should ensure that the constraints on the key columns are maintained when
180 * a <code>CachedRowSet</code> object sets a primary key column as a match column.
181 *
182 * @param columnName a <code>String</code> object giving the name of the column
183 * to be set as the match column
184 * @throws SQLException if an invalid column name is set, the column name
185 * is a null, or the column name is an empty string
186 * @see #unsetMatchColumn
187 * @see #setMatchColumn(int[])
188 */
189 public void setMatchColumn(String columnName) throws SQLException;
190
191 /**
192 * Sets the designated columns as the match column for this <code>RowSet</code>
193 * object. A <code>JoinRowSet</code> object can now add this <code>RowSet</code>
194 * object based on the match column.
195 *
196 * @param columnNames an array of <code>String</code> objects giving the names
197 * of the column to be set as the match columns
198 * @throws SQLException if an invalid column name is set, the column name
199 * is a null, or the column name is an empty string
200 * @see #unsetMatchColumn
201 * @see #setMatchColumn(int[])
202 */
203 public void setMatchColumn(String[] columnNames) throws SQLException;
204
205 /**
206 * Retrieves the indexes of the match columns that were set for this
207 * <code>RowSet</code> object with the method
208 * <code>setMatchColumn(int[] columnIdxes)</code>.
209 *
210 * @return an <code>int</code> array identifying the indexes of the columns
211 * that were set as the match columns for this <code>RowSet</code> object
212 * @throws SQLException if no match column has been set
213 * @see #setMatchColumn
214 * @see #unsetMatchColumn
215 */
216 public int[] getMatchColumnIndexes() throws SQLException;
217
218 /**
219 * Retrieves the names of the match columns that were set for this
220 * <code>RowSet</code> object with the method
221 * <code>setMatchColumn(String [] columnNames)</code>.
222 *
223 * @return an array of <code>String</code> objects giving the names of the columns
224 * set as the match columns for this <code>RowSet</code> object
225 * @throws SQLException if no match column has been set
226 * @see #setMatchColumn
227 * @see #unsetMatchColumn
228 *
229 */
230 public String[] getMatchColumnNames() throws SQLException;
231
232 /**
233 * Unsets the designated column as the match column for this <code>RowSet</code>
234 * object.
235 * <P>
236 * <code>RowSet</code> objects that implement the <code>Joinable</code> interface
237 * must ensure that a key-like constraint continues to be enforced until the
238 * method <code>CachedRowSet.unsetKeyColumns</code> has been called on the
239 * designated column.
240 *
241 * @param columnIdx an <code>int</code> that identifies the index of the column
242 * that is to be unset as a match column
243 * @throws SQLException if an invalid column index is designated or if
244 * the designated column was not previously set as a match
245 * column
246 * @see #setMatchColumn
247 */
248 public void unsetMatchColumn(int columnIdx) throws SQLException;
249
250 /**
251 * Unsets the designated columns as the match column for this <code>RowSet</code>
252 * object.
253 *
254 * @param columnIdxes an array of <code>int</code> that identifies the indexes
255 * of the columns that are to be unset as match columns
256 * @throws SQLException if an invalid column index is designated or if
257 * the designated column was not previously set as a match
258 * column
259 * @see #setMatchColumn
260 */
261 public void unsetMatchColumn(int[] columnIdxes) throws SQLException;
262
263 /**
264 * Unsets the designated column as the match column for this <code>RowSet</code>
265 * object.
266 * <P>
267 * <code>RowSet</code> objects that implement the <code>Joinable</code> interface
268 * must ensure that a key-like constraint continues to be enforced until the
269 * method <code>CachedRowSet.unsetKeyColumns</code> has been called on the
270 * designated column.
271 *
272 * @param columnName a <code>String</code> object giving the name of the column
273 * that is to be unset as a match column
274 * @throws SQLException if an invalid column name is designated or
275 * the designated column was not previously set as a match
276 * column
277 * @see #setMatchColumn
278 */
279 public void unsetMatchColumn(String columnName) throws SQLException;
280
281 /**
282 * Unsets the designated columns as the match columns for this <code>RowSet</code>
283 * object.
284 *
285 * @param columnName an array of <code>String</code> objects giving the names of
286 * the columns that are to be unset as the match columns
287 * @throws SQLException if an invalid column name is designated or the
288 * designated column was not previously set as a match column
289 * @see #setMatchColumn
290 */
291 public void unsetMatchColumn(String[] columnName) throws SQLException;
292 }