Java tutorial
/* * Copyright 2009 Ahmad Hassan, 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 java.text.MessageFormat; import java.util.Properties; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.exolab.castor.jdo.PersistenceException; 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.castor.cpa.persistence.sql.keygen.typehandler.KeyGeneratorTypeHandlerString; import org.exolab.castor.mapping.MappingException; import org.exolab.castor.persist.spi.PersistenceFactory; /** * Extends AbstractBeforeKeyGenerator and implements additional methods specific * to Sequence Key generator. It invovles the fetching the Table ID before the * record is inserted into the table. * * @author <a href="mailto:ahmad DOT hassan AT gmail DOT com">Ahmad Hassan</a> * @author <a href="mailto:ralf DOT joachim AT syscon DOT eu">Ralf Joachim</a> * @version $Revision$ $Date$ */ public final class SequenceBeforeKeyGenerator 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(SequenceBeforeKeyGenerator.class); /** Key length used for KeyGeneratorTypeHandlerString. */ private static final int STRING_KEY_LENGTH = 8; /** Persistence factory for the database engine the entity is persisted in. * Used to format the SQL statement. */ private PersistenceFactory _factory; /** Sequence name associated with the table. */ private String _seqName; /** Value used in fetching identity from Interbase database. */ private int _increment; /** Particular type handler instance. */ private KeyGeneratorTypeHandler<? extends Object> _typeHandler; //----------------------------------------------------------------------------------- /** * Initialize the SEQUENCE key generator for BEFORE_INSERT style * {@link #generateKey} is called before INSERT. * * @param factory A PersistenceFactory instance. * @param params Database specific properties. * @param sqlType A SQLTypidentifier. * @throws MappingException if this key generator is not compatible with the * persistance factory. */ public SequenceBeforeKeyGenerator(final PersistenceFactory factory, final Properties params, final int sqlType) throws MappingException { super(factory); _factory = factory; _seqName = params.getProperty("sequence", "{0}_seq"); try { _increment = Integer.parseInt(params.getProperty("increment", "1")); } catch (NumberFormatException nfe) { _increment = 1; } initSqlTypeHandler(sqlType); } /** * Initialize the Handler based on SQL Type. * * @param sqlType A SQLTypidentifier. */ protected void initSqlTypeHandler(final int sqlType) { if (sqlType == Types.INTEGER) { _typeHandler = new KeyGeneratorTypeHandlerInteger(true); } else if (sqlType == Types.BIGINT) { _typeHandler = new KeyGeneratorTypeHandlerLong(true); } else if ((sqlType == Types.CHAR) || (sqlType == Types.VARCHAR)) { _typeHandler = new KeyGeneratorTypeHandlerString(true, STRING_KEY_LENGTH); } else { _typeHandler = new KeyGeneratorTypeHandlerBigDecimal(true); } } /** * Formats the sequence name using name of the table and ID. * * @param tableName Name of the table. * @param primKeyName ID of the table. * @return String representing formatted sequence name. */ private String getSeqName(final String tableName, final String primKeyName) { return MessageFormat.format(_seqName, new Object[] { tableName, primKeyName }); } //----------------------------------------------------------------------------------- /** * @param conn An open connection within the given transaction. * @param tableName The table name. * @param primKeyName The primary key name. * @return A new key. * @throws PersistenceException An error occured talking to persistent storage. */ public Object generateKey(final Connection conn, final String tableName, final String primKeyName) throws PersistenceException { PreparedStatement stmt = null; ResultSet rs = null; try { // prepares the statement String sql = _factory.getSequenceBeforeSelectString(getSeqName(tableName, primKeyName), tableName, _increment); stmt = conn.prepareStatement(sql); // execute the prepared statement rs = stmt.executeQuery(); // process result set using appropriate handler and return its value return _typeHandler.getValue(rs); } catch (SQLException e) { String msg = Messages.format("persist.keyGenSQL", this.getClass().getName(), e.toString()); throw new PersistenceException(msg); } finally { try { if (rs != null) { rs.close(); } if (stmt != null) { stmt.close(); } } catch (SQLException e) { LOG.warn("Problem closing JDBC statement", e); } } } /** * {@inheritDoc} */ public boolean isInSameConnection() { return true; } //----------------------------------------------------------------------------------- }