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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.
* <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 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> 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;
}