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/* * 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 $Revision$ $Date$ */ 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; } //----------------------------------------------------------------------------------- }