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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.
 *
 * <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 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
 *
 */

 // <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.
 * @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;

}