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 java.sql.*; import javax.sql.*; import javax.naming.*; import java.io.*; import java.math.*; /** * The standard interface that all standard implementations of * <code>FilteredRowSet</code> must implement. The <code>FilteredRowSetImpl</code> class * provides the reference implementation which may be extended if required. * Alternatively, a vendor is free to implement its own version * by implementing this interface. * * <h2>1.0 Background</h2> * * There are occasions when a <code>RowSet</code> object has a need to provide a degree * of filtering to its contents. One possible solution is to provide * a query language for all standard <code>RowSet</code> implementations; however, * this is an impractical approach for lightweight components such as disconnected * <code>RowSet</code> * objects. The <code>FilteredRowSet</code> interface seeks to address this need * without supplying a heavyweight query language along with the processing that * such a query language would require. * <p> * A JDBC <code>FilteredRowSet</code> standard implementation implements the * <code>RowSet</code> interfaces and extends the * <code>CachedRowSet</code>™ class. The * <code>CachedRowSet</code> class provides a set of protected cursor manipulation * methods, which a <code>FilteredRowSet</code> implementation can override * to supply filtering support. * * <h2>2.0 Predicate Sharing</h2> * * If a <code>FilteredRowSet</code> implementation is shared using the * inherited <code>createShared</code> method in parent interfaces, the * <code>Predicate</code> should be shared without modification by all * <code>FilteredRowSet</code> instance clones. * * <h2>3.0 Usage</h2> * <p> * By implementing a <code>Predicate</code> (see example in <a href="Predicate.html">Predicate</a> * class JavaDoc), a <code>FilteredRowSet</code> could then be used as described * below. * * <pre> * {@code * FilteredRowSet frs = new FilteredRowSetImpl(); * frs.populate(rs); * * Range name = new Range("Alpha", "Bravo", "columnName"); * frs.setFilter(name); * * frs.next() // only names from "Alpha" to "Bravo" will be returned * } * </pre> * In the example above, we initialize a <code>Range</code> object which * implements the <code>Predicate</code> interface. This object expresses * the following constraints: All rows outputted or modified from this * <code>FilteredRowSet</code> object must fall between the values 'Alpha' and * 'Bravo' both values inclusive, in the column 'columnName'. If a filter is * applied to a <code>FilteredRowSet</code> object that contains no data that * falls within the range of the filter, no rows are returned. * <p> * This framework allows multiple classes implementing predicates to be * used in combination to achieved the required filtering result with * out the need for query language processing. * * <h2>4.0 Updating a <code>FilteredRowSet</code> Object</h2> * The predicate set on a <code>FilteredRowSet</code> object * applies a criterion on all rows in a * <code>RowSet</code> object to manage a subset of rows in a <code>RowSet</code> * object. This criterion governs the subset of rows that are visible and also * defines which rows can be modified, deleted or inserted. * <p> * Therefore, the predicate set on a <code>FilteredRowSet</code> object must be * considered as bi-directional and the set criterion as the gating mechanism * for all views and updates to the <code>FilteredRowSet</code> object. Any attempt * to update the <code>FilteredRowSet</code> that violates the criterion will * result in a <code>SQLException</code> object being thrown. * <p> * The <code>FilteredRowSet</code> range criterion can be modified by applying * a new <code>Predicate</code> object to the <code>FilteredRowSet</code> * instance at any time. This is possible if no additional references to the * <code>FilteredRowSet</code> object are detected. A new filter has an * immediate effect on criterion enforcement within the * <code>FilteredRowSet</code> object, and all subsequent views and updates will be * subject to similar enforcement. * * <h2>5.0 Behavior of Rows Outside the Filter</h2> * Rows that fall outside of the filter set on a <code>FilteredRowSet</code> * object cannot be modified until the filter is removed or a * new filter is applied. * <p> * Furthermore, only rows that fall within the bounds of a filter will be * synchronized with the data source. * * @author Jonathan Bruce * @since 1.5 */ public interface FilteredRowSet extends WebRowSet { /** * Applies the given <code>Predicate</code> object to this * <code>FilteredRowSet</code> * object. The filter applies controls both to inbound and outbound views, * constraining which rows are visible and which * rows can be manipulated. * <p> * A new <code>Predicate</code> object may be set at any time. This has the * effect of changing constraints on the <code>RowSet</code> object's data. * In addition, modifying the filter at runtime presents issues whereby * multiple components may be operating on one <code>FilteredRowSet</code> object. * Application developers must take responsibility for managing multiple handles * to <code>FilteredRowSet</code> objects when their underling <code>Predicate</code> * objects change. * * @param p a <code>Predicate</code> object defining the filter for this * <code>FilteredRowSet</code> object. Setting a <b>null</b> value * will clear the predicate, allowing all rows to become visible. * * @throws SQLException if an error occurs when setting the * <code>Predicate</code> object */ public void setFilter(Predicate p) throws SQLException; /** * Retrieves the active filter for this <code>FilteredRowSet</code> object. * * @return p the <code>Predicate</code> for this <code>FilteredRowSet</code> * object; <code>null</code> if no filter has been set. */ public Predicate getFilter(); }