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
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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24 */
25
26 package javax.sql.rowset;
27
28 import javax.sql.*;
29 import java.sql.*;
30
31 /**
32 * The standard interface that provides the framework for all
33 * <code>FilteredRowSet</code> objects to describe their filters.
34 *
35 * <h3>1.0 Background</h3>
36 * The <code>Predicate</code> interface is a standard interface that
37 * applications can implement to define the filter they wish to apply to a
38 * a <code>FilteredRowSet</code> object. A <code>FilteredRowSet</code>
39 * object consumes implementations of this interface and enforces the
40 * constraints defined in the implementation of the method <code>evaluate</code>.
41 * A <code>FilteredRowSet</code> object enforces the filter constraints in a
42 * bi-directional manner: It outputs only rows that are within
43 * the constraints of the filter; and conversely, it inserts, modifies, or updates
44 * only rows that are within the constraints of the filter.
45 *
46 * <h3>2.0 Implementation Guidelines</h3>
47 * In order to supply a predicate for the <code>FilteredRowSet</code>.
48 * this interface must be implemented. At this time, the JDBC RowSet
49 * Implementations (JSR-114) does not specify any standard filters definitions.
50 * By specifying a standard means and mechanism for a range of filters to be
51 * defined and deployed with both the reference and vendor implementations
52 * of the <code>FilteredRowSet</code> interface, this allows for a flexible
53 * and application motivated implementations of <code>Predicate</code> to emerge.
54 * <p>
55 * A sample implementation would look something like this:
56 * <pre>{@code
57 * public class Range implements Predicate {
58 *
59 * private int[] lo;
60 * private int[] hi;
61 * private int[] idx;
62 *
63 * public Range(int[] lo, int[] hi, int[] idx) {
64 * this.lo = lo;
65 * this.hi = hi;
66 * this.idx = idx;
67 * }
68 *
69 * public boolean evaluate(RowSet rs) {
70 *
71 * // Check the present row determine if it lies
72 * // within the filtering criteria.
73 *
74 * for (int i = 0; i < idx.length; i++) {
75 * int value;
76 * try {
77 * value = (Integer) rs.getObject(idx[i]);
78 * } catch (SQLException ex) {
79 * Logger.getLogger(Range.class.getName()).log(Level.SEVERE, null, ex);
80 * return false;
81 * }
82 *
83 * if (value < lo[i] && value > hi[i]) {
84 * // outside of filter constraints
85 * return false;
86 * }
87 * }
88 * // Within filter constraints
89 * return true;
90 * }
91 * }
92 * }</pre>
93 * <P>
94 * The example above implements a simple range predicate. Note, that
95 * implementations should but are not required to provide <code>String</code>
96 * and integer index based constructors to provide for JDBC RowSet Implementation
97 * applications that use both column identification conventions.
98 *
99 * @author Jonathan Bruce, Amit Handa
100 * @since 1.5
101 *
102 */
103
104 // <h3>3.0 FilteredRowSet Internals</h3>
105 // internalNext, Frist, Last. Discuss guidelines on how to approach this
106 // and cite examples in reference implementations.
107 public interface Predicate {
108 /**
109 * This method is typically called a <code>FilteredRowSet</code> object
110 * internal methods (not public) that control the <code>RowSet</code> object's
111 * cursor moving from row to the next. In addition, if this internal method
112 * moves the cursor onto a row that has been deleted, the internal method will
113 * continue to ove the cursor until a valid row is found.
114 * @param rs The {@code RowSet} to be evaluated
115 * @return <code>true</code> if there are more rows in the filter;
116 * <code>false</code> otherwise
117 */
118 public boolean evaluate(RowSet rs);
119
120
121 /**
122 * This method is called by a <code>FilteredRowSet</code> object
123 * to check whether the value lies between the filtering criterion (or criteria
124 * if multiple constraints exist) set using the <code>setFilter()</code> method.
125 * <P>
126 * The <code>FilteredRowSet</code> object will use this method internally
127 * while inserting new rows to a <code>FilteredRowSet</code> instance.
128 *
129 * @param value An <code>Object</code> value which needs to be checked,
130 * whether it can be part of this <code>FilterRowSet</code> object.
131 * @param column a <code>int</code> object that must match the
132 * SQL index of a column in this <code>RowSet</code> object. This must
133 * have been passed to <code>Predicate</code> as one of the columns
134 * for filtering while initializing a <code>Predicate</code>
135 * @return <code>true</code> if row value lies within the filter;
136 * <code>false</code> otherwise
137 * @throws SQLException if the column is not part of filtering criteria
138 */
139 public boolean evaluate(Object value, int column) throws SQLException;
140
141 /**
142 * This method is called by the <code>FilteredRowSet</code> object
143 * to check whether the value lies between the filtering criteria set
144 * using the setFilter method.
145 * <P>
146 * The <code>FilteredRowSet</code> object will use this method internally
147 * while inserting new rows to a <code>FilteredRowSet</code> instance.
148 *
149 * @param value An <code>Object</code> value which needs to be checked,
150 * whether it can be part of this <code>FilterRowSet</code>.
151 *
152 * @param columnName a <code>String</code> object that must match the
153 * SQL name of a column in this <code>RowSet</code>, ignoring case. This must
154 * have been passed to <code>Predicate</code> as one of the columns for filtering
155 * while initializing a <code>Predicate</code>
156 *
157 * @return <code>true</code> if value lies within the filter; <code>false</code> otherwise
158 *
159 * @throws SQLException if the column is not part of filtering criteria
160 */
161 public boolean evaluate(Object value, String columnName) throws SQLException;
162
163 }