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/*
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* Copyright (c) 2003, 2004, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package javax.sql.rowset;
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import javax.sql.*;
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import java.sql.*;
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/**
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* The standard interface that provides the framework for all
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* <code>FilteredRowSet</code> objects to describe their filters.
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* <p>
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* <h3>1.0 Background</h3>
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* The <code>Predicate</code> interface is a standard interface that
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* applications can implement to define the filter they wish to apply to a
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* a <code>FilteredRowSet</code> object. A <code>FilteredRowSet</code>
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* object consumes implementations of this interface and enforces the
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* constraints defined in the implementation of the method <code>evaluate</code>.
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* A <code>FilteredRowSet</code> object enforces the filter constraints in a
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* bi-directional manner: It outputs only rows that are within
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* the constraints of the filter; and conversely, it inserts, modifies, or updates
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* only rows that are within the constraints of the filter.
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*
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* <h3>2.0 Implementation Guidelines</h3>
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* In order to supply a predicate for the <code>FilteredRowSet</code>.
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* this interface must be implemented. At this time, the JDBC RowSet
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* Implementations (JSR-114) does not specify any standard filters definitions.
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* By specifying a standard means and mechanism for a range of filters to be
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* defined and deployed with both the reference and vendor implementations
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* of the <code>FilteredRowSet</code> interface, this allows for a flexible
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* and application motivated implementations of <code>Predicate</code> to emerge.
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* <p>
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* A sample implementation would look something like this:
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* <pre>
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* <code>
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* public class Range implements Predicate {
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*
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* private Object lo[];
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* private Object hi[];
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* private int idx[];
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*
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* public Range(Object[] lo, Object[] hi, int[] idx) {
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* this.lo = lo;
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* this.hi = hi;
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* this.idx = idx;
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* }
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*
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* public boolean evaluate(RowSet rs) {
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* CachedRowSet crs = (CachedRowSet)rs;
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* boolean bool1,bool2;
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*
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* // Check the present row determine if it lies
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* // within the filtering criteria.
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*
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* for (int i = 0; i < idx.length; i++) {
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*
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* if ((rs.getObject(idx[i]) >= lo[i]) &&
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* (rs.getObject(idx[i]) >= hi[i]) {
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* bool1 = true; // within filter constraints
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* } else {
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* bool2 = true; // outside of filter constraints
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* }
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* }
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*
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* if (bool2) {
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* return false;
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* } else {
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* return true;
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* }
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* }
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* </code>
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* </pre>
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* <P>
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* The example above implements a simple range predicate. Note, that
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* implementations should but are not required to provider <code>String</code>
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* and integer index based constructors to provide for JDBC RowSet Implementation
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* applications that use both column identification conventions.
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*
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* @author Jonathan Bruce, Amit Handa
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*
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*/
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// <h3>3.0 FilteredRowSet Internals</h3>
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// internalNext, Frist, Last. Discuss guidelines on how to approach this
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// and cite examples in reference implementations.
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public interface Predicate {
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/**
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* This method is typically called a <code>FilteredRowSet</code> object
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* internal methods (not public) that control the <code>RowSet</code> object's
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* cursor moving from row to the next. In addition, if this internal method
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* moves the cursor onto a row that has been deleted, the internal method will
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* continue to ove the cursor until a valid row is found.
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*
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* @return <code>true</code> if there are more rows in the filter;
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* <code>false</code> otherwise
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*/
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public boolean evaluate(RowSet rs);
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/**
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* This method is called by a <code>FilteredRowSet</code> object
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* to check whether the value lies between the filtering criterion (or criteria
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* if multiple constraints exist) set using the <code>setFilter()</code> method.
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* <P>
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* The <code>FilteredRowSet</code> object will use this method internally
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* while inserting new rows to a <code>FilteredRowSet</code> instance.
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*
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* @param value An <code>Object</code> value which needs to be checked,
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* whether it can be part of this <code>FilterRowSet</code> object.
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* @param column a <code>int</code> object that must match the
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* SQL index of a column in this <code>RowSet</code> object. This must
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* have been passed to <code>Predicate</code> as one of the columns
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* for filtering while initializing a <code>Predicate</code>
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* @return <code>true</code> ifrow value lies within the filter;
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* <code>false</code> otherwise
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* @throws SQLException if the column is not part of filtering criteria
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*/
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public boolean evaluate(Object value, int column) throws SQLException;
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/**
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* This method is called by the <code>FilteredRowSet</code> object
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* to check whether the value lies between the filtering criteria set
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* using the setFilter method.
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* <P>
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* The <code>FilteredRowSet</code> object will use this method internally
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* while inserting new rows to a <code>FilteredRowSet</code> instance.
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*
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* @param value An <code>Object</code> value which needs to be checked,
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* whether it can be part of this <code>FilterRowSet</code>.
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*
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* @param columnName a <code>String</code> object that must match the
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* SQL name of a column in this <code>RowSet</code>, ignoring case. This must
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* have been passed to <code>Predicate</code> as one of the columns for filtering
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* while initializing a <code>Predicate</code>
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*
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* @return <code>true</code> if value lies within the filter; <code>false</code> otherwise
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*
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* @throws SQLException if the column is not part of filtering criteria
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*/
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public boolean evaluate(Object value, String columnName) throws SQLException;
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}
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