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25
26package javax.sql.rowset;
27
28import javax.sql.*;
29import 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, First, Last. Discuss guidelines on how to approach this
106 // and cite examples in reference implementations.
107public 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}
164