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  package org.apache.cayenne.access;
  
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.cayenne.ObjectId;
  import org.apache.cayenne.ResultIterator;
  import org.apache.cayenne.query.Query;
  
  /**
   * Defines a set of callback methods that allow {@link QueryEngine} to pass back query
   * results and notify caller about exceptions.
   */
  public interface OperationObserver extends OperationHints {
  
      /**
       * Callback method invoked after an updating query is executed.
       */
      void nextCount(Query query, int resultCount);
  
      /**
       * Callback method invoked after a batch update is executed.
       */
      void nextBatchCount(Query query, int[] resultCount);
  
      /**
       * Callback method invoked for each processed ResultSet.
       * 
       * @since 3.0
       */
      void nextRows(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
       * {@link #nextRows(Query, List)}.
       * 
       * @since 3.0
       */
      void nextRows(Query q, ResultIterator<?> it);
  
      /**
       * Callback method invoked after each batch of generated values is read during an update.
       * @since 4.2
       */
      void nextGeneratedRows(Query query, ResultIterator<?> keys, List<ObjectId> idsToUpdate);
  
      /**
       * Callback method invoked on exceptions that happen during an execution of a specific
       * query.
       */
      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.
       */
      void nextGlobalException(Exception ex);
  }
  