Java tutorial
/* * Copyright 2008 Oleg Nitz, 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.math.BigDecimal; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Types; import java.util.HashMap; import java.util.Map; import java.util.Properties; 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.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.engine.JDBCSyntax; import org.exolab.castor.mapping.MappingException; import org.exolab.castor.persist.spi.PersistenceFactory; import org.exolab.castor.persist.spi.QueryExpression; /** * HIGH-LOW key generators. * * @see HighLowKeyGeneratorFactory * @author <a href="mailto:on AT ibis DOT odessa DOT ua">Oleg Nitz</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 HighLowKeyGenerator 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(HighLowKeyGenerator.class); /** String constant for table. */ private static final String SEQ_TABLE = "table"; /** String constant for key-column. */ private static final String SEQ_KEY = "key-column"; /** String constant for value-column. */ private static final String SEQ_VALUE = "value-column"; /** String constant for grab-size. */ private static final String GRAB_SIZE = "grab-size"; /** String constant for same-connection. */ private static final String SAME_CONNECTION = "same-connection"; /** String constant for global. */ private static final String GLOBAL = "global"; /** String constant for global key. */ private static final String GLOBAL_KEY = "global-key"; /** Int constant. */ private static final int UPDATE_PARAM_MAX = 1; /** Int constant. */ private static final int UPDATE_PARAM_TABLE = 2; /** Int constant. */ private static final int UPDATE_PARAM_LAST = 3; /** Int constant. */ private static final int INSERT_PARAM_TABLE = 1; /** Int constant. */ private static final int INSERT_PARAM_MAX = 2; /** Int constant. */ private static final int LOCK_TRIALS = 7; /** Map to store value handler. */ private final Map<String, HighLowValueHandler<? extends Object>> _handlers = new HashMap<String, HighLowValueHandler<? extends Object>>(); /** Persistence factory for the database engine the entity is persisted in. * Used to format the SQL statement. */ private final PersistenceFactory _factory; /** Databse engine type. */ private final int _sqlType; /** Sequence table name. */ private String _seqTable; /** Sequence table key column name. */ private String _seqKey; /** Sequence table value column name. */ private String _seqValue; /** Grab size. */ private int _grabSize; /** Shell the same connection be used? * <br/> * Note: This is less efficient, but in EJB envirinment we have no choice for now. */ private boolean _sameConnection; /** Shell globally unique identities be generated? */ private boolean _global; /** If globally unique identities are generated, then which key needs to be used? */ private String _globalKey; //----------------------------------------------------------------------------------- /** * Initialize the HIGH-LOW key generator. * * @param factory A PersistenceFactory instance. * @param params Database engine specific parameters. * @param sqlType A SQLTypidentifier. * @throws MappingException if this key generator is not compatible with the * persistance factory. */ public HighLowKeyGenerator(final PersistenceFactory factory, final Properties params, final int sqlType) throws MappingException { super(factory); _factory = factory; _sqlType = sqlType; 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); } initFromParameters(params); } /** Method to init some class variables. * * @param params Database engine specific parameters. * @throws MappingException if this key generator is not compatible with the * persistance factory. */ public void initFromParameters(final Properties params) throws MappingException { _seqTable = params.getProperty(SEQ_TABLE); if (_seqTable == null) { throw new MappingException( Messages.format("mapping.KeyGenParamNotSet", SEQ_TABLE, getClass().getName())); } _seqKey = params.getProperty(SEQ_KEY); if (_seqKey == null) { throw new MappingException(Messages.format("mapping.KeyGenParamNotSet", SEQ_KEY, getClass().getName())); } _seqValue = params.getProperty(SEQ_VALUE); if (_seqValue == null) { throw new MappingException( Messages.format("mapping.KeyGenParamNotSet", SEQ_VALUE, getClass().getName())); } String grabSize = params.getProperty(GRAB_SIZE, "10"); try { _grabSize = Integer.parseInt(grabSize); } catch (NumberFormatException except) { _grabSize = 0; } if (_grabSize <= 0) { throw new MappingException( Messages.format("mapping.wrongKeyGenParam", grabSize, GRAB_SIZE, getClass().getName())); } _sameConnection = "true".equals(params.getProperty(SAME_CONNECTION)); _global = "true".equals(params.getProperty(GLOBAL)); _globalKey = params.getProperty(GLOBAL_KEY); if (_globalKey == null) { _globalKey = "<GLOBAL>"; } } //----------------------------------------------------------------------------------- /** * {@inheritDoc} */ public synchronized Object generateKey(final Connection conn, final String tableName, final String primKeyName) throws PersistenceException { String intTableName = tableName; if (_global) { intTableName = _globalKey; } HighLowValueHandler<? extends Object> handler = _handlers.get(intTableName); if (handler == null) { if (_sqlType == Types.INTEGER) { KeyGeneratorTypeHandlerInteger typeHandler = new KeyGeneratorTypeHandlerInteger(false); handler = new HighLowValueHandler<Integer>(intTableName, _grabSize, typeHandler); } else if (_sqlType == Types.BIGINT) { KeyGeneratorTypeHandlerLong typeHandler = new KeyGeneratorTypeHandlerLong(false); handler = new HighLowValueHandler<Long>(intTableName, _grabSize, typeHandler); } else { KeyGeneratorTypeHandlerBigDecimal typeHandler = new KeyGeneratorTypeHandlerBigDecimal(false); handler = new HighLowValueHandler<BigDecimal>(intTableName, _grabSize, typeHandler); } _handlers.put(intTableName, handler); } if (!handler.hasNext()) { // Create "SELECT seq_val FROM seq_table WHERE seq_key='table'" // with database-dependent keyword for lock // Note: Some databases (InstantDB, HypersonicSQL) don't support such locks. QueryExpression query = _factory.getQueryExpression(); query.addColumn(_seqTable, _seqValue); query.addCondition(_seqTable, _seqKey, QueryExpression.OP_EQUALS, JDBCSyntax.PARAMETER); String lockSQL = query.getStatement(true); // For the case that "SELECT FOR UPDATE" is not supported, perform dirty checking String updateSQL = "UPDATE " + _seqTable + " SET " + _seqValue + "=" + JDBCSyntax.PARAMETER + JDBCSyntax.WHERE + _seqKey + QueryExpression.OP_EQUALS + JDBCSyntax.PARAMETER + JDBCSyntax.AND + _seqValue + QueryExpression.OP_EQUALS + JDBCSyntax.PARAMETER; String maxSQL = JDBCSyntax.SELECT + "MAX(" + primKeyName + ") " + "FROM " + intTableName; String insertSQL = "INSERT INTO " + _seqTable + " (" + _seqKey + "," + _seqValue + ") VALUES (?, ?)"; PreparedStatement stmt = null; try { // Separate connection should be committed/rolled back at this point if (!_sameConnection) { conn.rollback(); } // Retry 7 times (lucky number) boolean success = false; for (int i = 0; !success && (i < LOCK_TRIALS); i++) { stmt = conn.prepareStatement(lockSQL); handler.bindTable(stmt, 1); ResultSet rs = stmt.executeQuery(); handler.init(rs); boolean found = rs.isFirst(); stmt.close(); if (found) { stmt = conn.prepareStatement(updateSQL); handler.bindMax(stmt, UPDATE_PARAM_MAX); handler.bindTable(stmt, UPDATE_PARAM_TABLE); handler.bindLast(stmt, UPDATE_PARAM_LAST); success = (stmt.executeUpdate() == 1); stmt.close(); } else { if (!_global) { stmt = conn.prepareStatement(maxSQL); rs = stmt.executeQuery(); handler.init(rs); stmt.close(); } stmt = conn.prepareStatement(insertSQL); handler.bindTable(stmt, INSERT_PARAM_TABLE); handler.bindMax(stmt, INSERT_PARAM_MAX); success = (stmt.executeUpdate() == 1); stmt.close(); } } if (success) { if (!_sameConnection) { conn.commit(); } } else { if (!_sameConnection) { conn.rollback(); } throw new PersistenceException(Messages.format("persist.keyGenFailed", getClass().getName())); } } catch (SQLException ex) { try { if (!_sameConnection) { conn.rollback(); } } catch (SQLException ex2) { LOG.warn("Problem rolling back JDBC transaction.", ex2); } throw new PersistenceException( Messages.format("persist.keyGenSQL", getClass().getName(), ex.toString()), ex); } finally { try { if (stmt != null) { stmt.close(); } } catch (SQLException ex) { LOG.warn(Messages.message("persist.stClosingFailed"), ex); } } } return handler.next(); } /** * {@inheritDoc} */ public boolean isInSameConnection() { return _sameConnection; } //----------------------------------------------------------------------------------- }