/* * Copyright (c) 2003, 2004, 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 * FilteredRowSet objects to describe their filters. *

*

1.0 Background

* The Predicate interface is a standard interface that * applications can implement to define the filter they wish to apply to a * a FilteredRowSet object. A FilteredRowSet * object consumes implementations of this interface and enforces the * constraints defined in the implementation of the method evaluate. * A FilteredRowSet 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. * *

2.0 Implementation Guidelines

* In order to supply a predicate for the FilteredRowSet. * 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 FilteredRowSet interface, this allows for a flexible * and application motivated implementations of Predicate to emerge. *

* A sample implementation would look something like this: *

 * 
 *    public class Range implements Predicate {
 *
 *       private Object lo[];
 *       private Object hi[];
 *       private int idx[];
 *
 *       public Range(Object[] lo, Object[] hi, int[] idx) {
 *          this.lo = lo;
 *          this.hi = hi;
 *          this.idx = idx;
 *       }
 *
 *      public boolean evaluate(RowSet rs) {
 *          CachedRowSet crs = (CachedRowSet)rs;
 *          boolean bool1,bool2;
 *
 *          // Check the present row determine if it lies
 *          // within the filtering criteria.
 *
 *          for (int i = 0; i < idx.length; i++) {
 *
 *              if ((rs.getObject(idx[i]) >= lo[i]) &&
 *                  (rs.getObject(idx[i]) >= hi[i]) {
 *                  bool1 = true; // within filter constraints
 *          } else {
 *            bool2 = true; // outside of filter constraints
 *          }
 *      }
 *
 *      if (bool2) {
 *         return false;
 *      } else {
 *         return true;
 *      }
 *  }
 * 
 * 
*

* The example above implements a simple range predicate. Note, that * implementations should but are not required to provider String * and integer index based constructors to provide for JDBC RowSet Implementation * applications that use both column identification conventions. * * @author Jonathan Bruce, Amit Handa * */ //

3.0 FilteredRowSet Internals

// internalNext, Frist, Last. Discuss guidelines on how to approach this // and cite examples in reference implementations. public interface Predicate { /** * This method is typically called a FilteredRowSet object * internal methods (not public) that control the RowSet 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. * * @return true if there are more rows in the filter; * false otherwise */ public boolean evaluate(RowSet rs); /** * This method is called by a FilteredRowSet object * to check whether the value lies between the filtering criterion (or criteria * if multiple constraints exist) set using the setFilter() method. *

* The FilteredRowSet object will use this method internally * while inserting new rows to a FilteredRowSet instance. * * @param value An Object value which needs to be checked, * whether it can be part of this FilterRowSet object. * @param column a int object that must match the * SQL index of a column in this RowSet object. This must * have been passed to Predicate as one of the columns * for filtering while initializing a Predicate * @return true ifrow value lies within the filter; * false 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 FilteredRowSet object * to check whether the value lies between the filtering criteria set * using the setFilter method. *

* The FilteredRowSet object will use this method internally * while inserting new rows to a FilteredRowSet instance. * * @param value An Object value which needs to be checked, * whether it can be part of this FilterRowSet. * * @param columnName a String object that must match the * SQL name of a column in this RowSet, ignoring case. This must * have been passed to Predicate as one of the columns for filtering * while initializing a Predicate * * @return true if value lies within the filter; false otherwise * * @throws SQLException if the column is not part of filtering criteria */ public boolean evaluate(Object value, String columnName) throws SQLException; }