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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.

 *

 * <h2>1.0 Background</h2>

 * 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.

 *

 * <h2>2.0 Implementation Guidelines</h2>

 * 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

 * @since 1.5

 *

 */

 // <h2>3.0 FilteredRowSet Internals</h2>

 // internalNext, First, 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;

}