001 /*
002 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.sql.rowset;
027
028 import javax.sql.*;
029 import java.sql.*;
030
031 /**
032 * The standard interface that provides the framework for all
033 * <code>FilteredRowSet</code> objects to describe their filters.
034 * <p>
035 * <h3>1.0 Background</h3>
036 * The <code>Predicate</code> interface is a standard interface that
037 * applications can implement to define the filter they wish to apply to a
038 * a <code>FilteredRowSet</code> object. A <code>FilteredRowSet</code>
039 * object consumes implementations of this interface and enforces the
040 * constraints defined in the implementation of the method <code>evaluate</code>.
041 * A <code>FilteredRowSet</code> object enforces the filter constraints in a
042 * bi-directional manner: It outputs only rows that are within
043 * the constraints of the filter; and conversely, it inserts, modifies, or updates
044 * only rows that are within the constraints of the filter.
045 *
046 * <h3>2.0 Implementation Guidelines</h3>
047 * In order to supply a predicate for the <code>FilteredRowSet</code>.
048 * this interface must be implemented. At this time, the JDBC RowSet
049 * Implementations (JSR-114) does not specify any standard filters definitions.
050 * By specifying a standard means and mechanism for a range of filters to be
051 * defined and deployed with both the reference and vendor implementations
052 * of the <code>FilteredRowSet</code> interface, this allows for a flexible
053 * and application motivated implementations of <code>Predicate</code> to emerge.
054 * <p>
055 * A sample implementation would look something like this:
056 * <pre>
057 * <code>
058 * public class Range implements Predicate {
059 *
060 * private Object lo[];
061 * private Object hi[];
062 * private int idx[];
063 *
064 * public Range(Object[] lo, Object[] hi, int[] idx) {
065 * this.lo = lo;
066 * this.hi = hi;
067 * this.idx = idx;
068 * }
069 *
070 * public boolean evaluate(RowSet rs) {
071 * CachedRowSet crs = (CachedRowSet)rs;
072 * boolean bool1,bool2;
073 *
074 * // Check the present row determine if it lies
075 * // within the filtering criteria.
076 *
077 * for (int i = 0; i < idx.length; i++) {
078 *
079 * if ((rs.getObject(idx[i]) >= lo[i]) &&
080 * (rs.getObject(idx[i]) >= hi[i]) {
081 * bool1 = true; // within filter constraints
082 * } else {
083 * bool2 = true; // outside of filter constraints
084 * }
085 * }
086 *
087 * if (bool2) {
088 * return false;
089 * } else {
090 * return true;
091 * }
092 * }
093 * </code>
094 * </pre>
095 * <P>
096 * The example above implements a simple range predicate. Note, that
097 * implementations should but are not required to provider <code>String</code>
098 * and integer index based constructors to provide for JDBC RowSet Implementation
099 * applications that use both column identification conventions.
100 *
101 * @author Jonathan Bruce, Amit Handa
102 *
103 */
104
105 // <h3>3.0 FilteredRowSet Internals</h3>
106 // internalNext, Frist, Last. Discuss guidelines on how to approach this
107 // and cite examples in reference implementations.
108 public interface Predicate {
109 /**
110 * This method is typically called a <code>FilteredRowSet</code> object
111 * internal methods (not public) that control the <code>RowSet</code> object's
112 * cursor moving from row to the next. In addition, if this internal method
113 * moves the cursor onto a row that has been deleted, the internal method will
114 * continue to ove the cursor until a valid row is found.
115 *
116 * @return <code>true</code> if there are more rows in the filter;
117 * <code>false</code> otherwise
118 */
119 public boolean evaluate(RowSet rs);
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> ifrow 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)
140 throws SQLException;
141
142 /**
143 * This method is called by the <code>FilteredRowSet</code> object
144 * to check whether the value lies between the filtering criteria set
145 * using the setFilter method.
146 * <P>
147 * The <code>FilteredRowSet</code> object will use this method internally
148 * while inserting new rows to a <code>FilteredRowSet</code> instance.
149 *
150 * @param value An <code>Object</code> value which needs to be checked,
151 * whether it can be part of this <code>FilterRowSet</code>.
152 *
153 * @param columnName a <code>String</code> object that must match the
154 * SQL name of a column in this <code>RowSet</code>, ignoring case. This must
155 * have been passed to <code>Predicate</code> as one of the columns for filtering
156 * while initializing a <code>Predicate</code>
157 *
158 * @return <code>true</code> if value lies within the filter; <code>false</code> otherwise
159 *
160 * @throws SQLException if the column is not part of filtering criteria
161 */
162 public boolean evaluate(Object value, String columnName)
163 throws SQLException;
164
165 }
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