Java tutorial
/* * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.sql.rowset; import javax.sql.*; import java.sql.*; /** * The standard interface that provides the framework for all * <code>FilteredRowSet</code> objects to describe their filters. * * <h2>1.0 Background</h2> * The <code>Predicate</code> interface is a standard interface that * applications can implement to define the filter they wish to apply to a * a <code>FilteredRowSet</code> object. A <code>FilteredRowSet</code> * object consumes implementations of this interface and enforces the * constraints defined in the implementation of the method <code>evaluate</code>. * A <code>FilteredRowSet</code> object enforces the filter constraints in a * bi-directional manner: It outputs only rows that are within * the constraints of the filter; and conversely, it inserts, modifies, or updates * only rows that are within the constraints of the filter. * * <h2>2.0 Implementation Guidelines</h2> * In order to supply a predicate for the <code>FilteredRowSet</code>. * this interface must be implemented. At this time, the JDBC RowSet * Implementations (JSR-114) does not specify any standard filters definitions. * By specifying a standard means and mechanism for a range of filters to be * defined and deployed with both the reference and vendor implementations * of the <code>FilteredRowSet</code> interface, this allows for a flexible * and application motivated implementations of <code>Predicate</code> to emerge. * <p> * A sample implementation would look something like this: * <pre>{@code * public class Range implements Predicate { * * private int[] lo; * private int[] hi; * private int[] idx; * * public Range(int[] lo, int[] hi, int[] idx) { * this.lo = lo; * this.hi = hi; * this.idx = idx; * } * * public boolean evaluate(RowSet rs) { * * // Check the present row determine if it lies * // within the filtering criteria. * * for (int i = 0; i < idx.length; i++) { * int value; * try { * value = (Integer) rs.getObject(idx[i]); * } catch (SQLException ex) { * Logger.getLogger(Range.class.getName()).log(Level.SEVERE, null, ex); * return false; * } * * if (value < lo[i] && value > hi[i]) { * // outside of filter constraints * return false; * } * } * // Within filter constraints * return true; * } * } * }</pre> * <P> * The example above implements a simple range predicate. Note, that * implementations should but are not required to provide <code>String</code> * and integer index based constructors to provide for JDBC RowSet Implementation * applications that use both column identification conventions. * * @author Jonathan Bruce, Amit Handa * @since 1.5 * */ // <h2>3.0 FilteredRowSet Internals</h2> // internalNext, First, Last. Discuss guidelines on how to approach this // and cite examples in reference implementations. public interface Predicate { /** * This method is typically called a <code>FilteredRowSet</code> object * internal methods (not public) that control the <code>RowSet</code> object's * cursor moving from row to the next. In addition, if this internal method * moves the cursor onto a row that has been deleted, the internal method will * continue to ove the cursor until a valid row is found. * @param rs The {@code RowSet} to be evaluated * @return <code>true</code> if there are more rows in the filter; * <code>false</code> otherwise */ public boolean evaluate(RowSet rs); /** * This method is called by a <code>FilteredRowSet</code> object * to check whether the value lies between the filtering criterion (or criteria * if multiple constraints exist) set using the <code>setFilter()</code> method. * <P> * The <code>FilteredRowSet</code> object will use this method internally * while inserting new rows to a <code>FilteredRowSet</code> instance. * * @param value An <code>Object</code> value which needs to be checked, * whether it can be part of this <code>FilterRowSet</code> object. * @param column a <code>int</code> object that must match the * SQL index of a column in this <code>RowSet</code> object. This must * have been passed to <code>Predicate</code> as one of the columns * for filtering while initializing a <code>Predicate</code> * @return <code>true</code> if row value lies within the filter; * <code>false</code> otherwise * @throws SQLException if the column is not part of filtering criteria */ public boolean evaluate(Object value, int column) throws SQLException; /** * This method is called by the <code>FilteredRowSet</code> object * to check whether the value lies between the filtering criteria set * using the setFilter method. * <P> * The <code>FilteredRowSet</code> object will use this method internally * while inserting new rows to a <code>FilteredRowSet</code> instance. * * @param value An <code>Object</code> value which needs to be checked, * whether it can be part of this <code>FilterRowSet</code>. * * @param columnName a <code>String</code> object that must match the * SQL name of a column in this <code>RowSet</code>, ignoring case. This must * have been passed to <code>Predicate</code> as one of the columns for filtering * while initializing a <code>Predicate</code> * * @return <code>true</code> if value lies within the filter; <code>false</code> otherwise * * @throws SQLException if the column is not part of filtering criteria */ public boolean evaluate(Object value, String columnName) throws SQLException; }