java/engine/org/apache/derby/catalog/TriggerNewTransitionRows.java

/*

   Derby - Class org.apache.derby.catalog.TriggerNewTransitionRows

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.catalog;

import org.apache.derby.iapi.db.Factory;
import org.apache.derby.iapi.db.TriggerExecutionContext;

import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.math.BigDecimal;

/**
 * Provides information about about a a set of new rows created by a
 * trigger action. 
 * 
 * <p>
 * You can only use this class if no JDBC 2.0 or later calls are made against it.
 *
 */
public final class TriggerNewTransitionRows extends org.apache.derby.vti.UpdatableVTITemplate 
{

	private ResultSet resultSet;

	/**
	 * Construct a VTI on the trigger's new row set.
	 * The new row set is the after image of the rows
	 * that are changed by the trigger.  For a trigger
	 * on a delete, this throws an exception.
	 * For a trigger on an update, this is the rows after
	 * they are updated.  For an insert, this is the rows
	 * that are inserted.
	 *
	 * @exception SQLException thrown if no trigger active
	 */
	public TriggerNewTransitionRows() throws SQLException
	{
		initializeResultSet();
	}

	private ResultSet initializeResultSet() throws SQLException {
		if (resultSet != null)
			resultSet.close();
		
		TriggerExecutionContext tec = Factory.getTriggerExecutionContext();
		if (tec == null)
		{
			throw new SQLException("There are no active triggers", "38000");
		}
		resultSet = tec.getNewRowSet();

		if (resultSet == null)
		{
			throw new SQLException("There is no new transition rows result set for this trigger", "38000");
		}
		return resultSet;
	}
    
    public ResultSetMetaData getMetaData() throws SQLException
    {
        return resultSet.getMetaData();
    }
    
   public ResultSet executeQuery() throws SQLException {
	   //DERBY-4095. Need to reinititialize ResultSet on 
       //executeQuery, in case it was closed in a NESTEDLOOP join.
       return initializeResultSet();
   }
    
   public int getResultSetConcurrency() {
        return ResultSet.CONCUR_READ_ONLY;
   }
   
   public void close() throws SQLException {
       resultSet.close();
   }
}