/*
* Copyright 2008 Oleg Nitz, Leonardo Souza Mario Bueno, Bruce Snyder, Ralf Joachim
*
* Licensed 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.castor.cpa.persistence.sql.keygen;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.castor.core.util.Messages;
import org.castor.cpa.persistence.sql.keygen.typehandler.KeyGeneratorTypeHandler;
import org.castor.cpa.persistence.sql.keygen.typehandler.KeyGeneratorTypeHandlerBigDecimal;
import org.castor.cpa.persistence.sql.keygen.typehandler.KeyGeneratorTypeHandlerInteger;
import org.castor.cpa.persistence.sql.keygen.typehandler.KeyGeneratorTypeHandlerLong;
import org.exolab.castor.jdo.PersistenceException;
import org.exolab.castor.jdo.QueryException;
import org.exolab.castor.mapping.MappingException;
import org.exolab.castor.persist.spi.PersistenceFactory;
import org.exolab.castor.persist.spi.QueryExpression;
/**
* MAX key generators.
*
* @see MaxKeyGeneratorFactory
* @author <a href="mailto:on AT ibis DOT odessa DOT ua">Oleg Nitz</a>
* @author <a href="mailto:leonardo AT itera DOT com DOT br">Leonardo Souza Mario Bueno</a>
* @author <a href="mailto:bruce DOT snyder AT gmail DOT com">Bruce Snyder</a>
* @author <a href="mailto:ralf DOT joachim AT syscon DOT eu">Ralf Joachim</a>
* @version $Revision$ $Date: 2006-04-25 15:08:23 -0600 (Tue, 25 Apr 2006) $
*/
public final class MaxKeyGenerator extends AbstractBeforeKeyGenerator {
//-----------------------------------------------------------------------------------
/** The <a href="http://jakarta.apache.org/commons/logging/">Jakarta
* Commons Logging</a> instance used for all logging. */
private static final Log LOG = LogFactory.getLog(MaxKeyGenerator.class);
/** Persistence factory for the database engine the entity is persisted in.
* Used to format the SQL statement. */
private final PersistenceFactory _factory;
/** Particular type handler instance. */
private KeyGeneratorTypeHandler<? extends Object> _typeHandler;
//-----------------------------------------------------------------------------------
/**
* Initialize the MAX key generator.
*
* @param factory A PersistenceFactory instance.
* @param sqlType A SQLTypidentifier.
* @throws MappingException if this key generator is not compatible with the
* persistance factory.
*/
public MaxKeyGenerator(final PersistenceFactory factory, final int sqlType)
throws MappingException {
super(factory);
_factory = factory;
if ((sqlType != Types.INTEGER) && (sqlType != Types.BIGINT)
&& (sqlType != Types.NUMERIC) && (sqlType != Types.DECIMAL)) {
String msg = Messages.format("mapping.keyGenSQLType",
getClass().getName(), new Integer(sqlType));
throw new MappingException(msg);
}
initSqlTypeHandler(sqlType);
}
/**
* Initialize the Handler based on SQL Type.
*
* @param sqlType A SQLTypidentifier.
*/
private void initSqlTypeHandler(final int sqlType) {
if (sqlType == Types.INTEGER) {
_typeHandler = new KeyGeneratorTypeHandlerInteger(false);
} else if (sqlType == Types.BIGINT) {
_typeHandler = new KeyGeneratorTypeHandlerLong(false);
} else {
_typeHandler = new KeyGeneratorTypeHandlerBigDecimal(false);
}
}
//-----------------------------------------------------------------------------------
/**
* Generate a new key for the specified table as "MAX(primary_key) + 1".
* If there is no records in the table, then the value 1 is returned.
* <br/>
* {@inheritDoc}
*/
public Object generateKey(final Connection conn, final String tableName,
final String primKeyName) throws PersistenceException {
PreparedStatement stmt = null;
try {
String sql = getQueryExpression(tableName, primKeyName);
stmt = conn.prepareStatement(sql);
ResultSet rs = stmt.executeQuery();
return _typeHandler.getNextValue(rs);
} catch (SQLException ex) {
throw new PersistenceException(Messages.format(
"persist.keyGenSQL", getClass().getName(), ex.toString()), ex);
} finally {
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
LOG.warn (Messages.message ("persist.stClosingFailed"), ex);
}
}
}
}
/**
* Get query string to retrive next primary key value.
*
* @param table The table name.
* @param column The primary key column name.
* @return The query string to retrive next primary key value.
* @throws QueryException The query cannot be constructed for this engine.
*/
private String getQueryExpression(final String table, final String column)
throws QueryException {
/*
* Pre 1.2.1 release of Castor we used a different query for MySQL that
* does not create a database lock. The only reason for doing so is, that
* MySQL has not supported such locks at some point. According to my tests
* this is not the case any more so I decided to comment out this special
* handling for MySQL as using locks may prevent us from getting
* DuplikateIdentityExceptions. (20.05.2008/RJ)
*
* // Create SQL sentence of the form
* // "SELECT MAX(pk) FROM table"
* // without lock
* QueryExpression query = _factory.getQueryExpression();
* query.addSelect("MAX(" + _factory.quoteName(column) + ")");
* query.addTable(table);
* return query.getStatement(false);
*/
// Create SQL sentence of the form
// "SELECT pk FROM table WHERE pk=(SELECT MAX(t1.pk) FROM table t1)"
// with database-dependent keyword for lock
QueryExpression query = _factory.getQueryExpression();
query.addColumn(table, column);
query.addCondition(table, column, QueryExpression.OP_EQUALS,
"(SELECT MAX(t1." + _factory.quoteName(column) + ") FROM "
+ _factory.quoteName(table) + " t1)");
return query.getStatement(true);
}
/**
* {@inheritDoc}
*/
public boolean isInSameConnection() {
return true;
}
//-----------------------------------------------------------------------------------
}