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/* * @(#)Predicate.java 1.6 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ 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. * <p> * <h3>1.0 Background</h3> * 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. * * <h3>2.0 Implementation Guidelines</h3> * 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 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; * } * } * </code> * </pre> * <P> * The example above implements a simple range predicate. Note, that * implementations should but are not required to provider <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 * */ // <h3>3.0 FilteredRowSet Internals</h3> // 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 <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. * * @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> ifrow 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; }