/**
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 2. Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* 3. The name "Exolab" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Intalio, Inc. For written permission,
* please contact info@exolab.org.
*
* 4. Products derived from this Software may not be called "Exolab"
* nor may "Exolab" appear in their names without prior written
* permission of Intalio, Inc. Exolab is a registered
* trademark of Intalio, Inc.
*
* 5. Due credit should be given to the Exolab Project
* (http://www.exolab.org/).
*
* THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
* NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* INTALIO, INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 1999 (C) Intalio, Inc. All Rights Reserved.
*
* $Id: SimpleQueryExecutor.java,v 1.1.1.1 2003/03/03 07:08:18 kvisco Exp $
*/
package org.exolab.castor.jdo.engine;
import java.util.NoSuchElementException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import org.exolab.castor.jdo.QueryResults;
import org.exolab.castor.jdo.PersistenceException;
import org.exolab.castor.jdo.QueryException;
import org.exolab.castor.persist.spi.QueryExpression;
/**
* A class to execute simple SQL queries generated from OQL. If the query
* only returns dependant values, or the results of SQL Functions or
* operations, then we don't need to use the whole persistence framework,
* and this class will execute the query, and return results.
*
* @author <a href="mailto:nissim@nksystems.com">Nissim Karpenstein</a>
* @version $Revision: 1.1.1.1 $ $Date: 2003/03/03 07:08:18 $
*/
public class SimpleQueryExecutor
{
private DatabaseImpl _dbImpl;
private Connection _conn = null;
private PreparedStatement _stmt = null;
private ResultSet _rset = null;
/**
* Constructor to create an object to execute a simple query.
*
* @param dbImpl the Database Implementation, used to get the connection
*/
public SimpleQueryExecutor(DatabaseImpl dbImpl) {
_dbImpl = dbImpl;
}
/**
* Executes a simple query and returns the results. The query must not
* return any complex objects, becuse this method can only return simple
* java objects.
*
* @param expr the Query Expression to be executed.
* @param bindValues the values of the parameters
* @throws QueryException if anything goes wrong.
* @return the results of the query.
*
*/
public QueryResults execute( QueryExpression expr, Object[] bindValues )
throws QueryException {
try {
_conn = DatabaseRegistry.createConnection( _dbImpl.getLockEngine() );
_stmt = _conn.prepareStatement( expr.getStatement(false) );
if ( bindValues != null ) {
for ( int i = 0 ; i < bindValues.length ; ++i ) {
_stmt.setObject( i + 1, bindValues[ i ] );
}
}
_rset = _stmt.executeQuery();
return new SimpleQueryResults();
}
catch (SQLException s) {
if ( _rset != null )
try { _rset.close(); } catch (SQLException e) {}
if ( _stmt != null )
try { _stmt.close(); } catch (SQLException e) {}
if ( _conn != null )
try { _conn.close(); } catch (SQLException e) {}
_rset = null;
_stmt = null;
_conn = null;
throw new QueryException( s.toString() );
}
}
public class SimpleQueryResults implements QueryResults {
private boolean _hasMore = false;
public SimpleQueryResults() {
//prime the resultset.
try {
_hasMore = _rset.next();
}
catch (SQLException e) {
_hasMore = false;
}
}
/**
* use the jdbc 2.0 method to move to an absolute position in the
* resultset.
*/
public boolean absolute(int row)
throws PersistenceException
{
boolean retval = false;
try
{
if (_rset != null)
{
retval = _rset.absolute(row);
}
}
catch (SQLException e)
{
throw new PersistenceException(e.getMessage());
}
return retval;
}
/**
* Uses the underlying db's cursors to most to the last row in the
* result set, get the row number via getRow(), then move back to
* where ever the user was positioned in the resultset.
*/
public int size()
throws PersistenceException
{
int whereIAm = 1; // first
int retval = 0; // default size is 0;
try
{
if (_rset != null)
{
whereIAm = _rset.getRow();
if (_rset.last())
{
retval = _rset.getRow();
}
else
{
retval = 0;
}
// go back from whence I came.
if (whereIAm > 0)
{
_rset.absolute(whereIAm);
}
else
{
_rset.beforeFirst();
}
}
}
catch (SQLException se)
{
throw new PersistenceException(se.getMessage());
}
return retval;
}
public boolean hasMoreElements() {
return _hasMore;
}
public boolean hasMore() throws PersistenceException {
return _hasMore;
}
public Object nextElement() throws NoSuchElementException {
try {
return next( true );
}
catch ( PersistenceException except ) {
// Will never happen
return null;
}
}
public Object next() throws PersistenceException, NoSuchElementException {
return next( false );
}
private Object next( boolean skipError )
throws PersistenceException, NoSuchElementException {
Object retVal = null;
if ( ! _hasMore )
throw new NoSuchElementException();
try {
retVal = _rset.getObject(1);
_hasMore = _rset.next();
}
catch ( SQLException except ) {
if ( ! skipError )
throw new PersistenceException(except.toString());
}
return retVal;
}
public void close() {
if ( _rset != null )
try { _rset.close(); } catch (SQLException s) {}
if ( _stmt != null )
try { _stmt.close(); } catch (SQLException s) {}
if ( _conn != null )
try { _conn.close(); } catch (SQLException s) {}
_rset = null;
_stmt = null;
_conn = null;
}
protected void finalize() throws Throwable {
close();
}
}
}