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package org.apache.cayenne.access;

import java.util.List;

import org.apache.cayenne.query.Query;

/**
 * Defines a set of callback methods that allow QueryEngine to pass back query results and
 * notify caller about exceptions.
 * 
 * @see org.apache.cayenne.access.QueryEngine
 * @author Andrus Adamchik
 */
// TODO: need a name that better reflects the functionality,
// e.g. OperationContext or QueryContext
public interface OperationObserver extends OperationHints {

    /**
     * Callback method invoked after an updating query is executed.
     */
    public void nextCount(Query query, int resultCount);

    /**
     * Callback method invoked after a batch update is executed.
     */
    public void nextBatchCount(Query query, int[] resultCount);

    /**
     * Callback method invoked for each processed ResultSet.
     */
    public void nextDataRows(Query query, List dataRows);

    /**
     * Callback method invoked for each opened ResultIterator. If this observer requested
     * results to be returned as a ResultIterator, this method is invoked instead of
     * "nextDataRows(Query,List)". OperationObserver is responsible for closing the
     * ResultIterators passed via this method.
     */
    public void nextDataRows(Query q, ResultIterator it);

    /**
     * Callback method invoked after each batch of generated values is read durring an
     * update.
     * 
     * @since 1.2
     */
    public void nextGeneratedDataRows(Query query, ResultIterator keysIterator);

    /**
     * Callback method invoked on exceptions that happen during an execution of a specific
     * query.
     */
    public void nextQueryException(Query query, Exception ex);

    /**
     * Callback method invoked on exceptions that are not tied to a specific query
     * execution, such as JDBC connection exceptions, etc.
     */
    public void nextGlobalException(Exception ex);
}
