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 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.apache.causeway.persistence.jdo.spring.integration;

import java.sql.SQLException;

import javax.jdo.JDOException;
import javax.jdo.PersistenceManager;
import javax.jdo.Transaction;

import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.datasource.ConnectionHandle;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionException;

/**
 * SPI strategy that allows for customizing integration with a specific JDO provider,
 * in particular regarding transaction management and exception translation. To be
 * implemented for specific JDO providers such as DataNucleus, Kodo, Lido, Versant Open Access.
 *
 * <p>JDO 3.0 defines standard ways for most of the functionality covered here.
 * Hence, Spring's {@link DefaultJdoDialect} uses the corresponding JDO 3.0 methods
 * by default, to be overridden in a vendor-specific fashion if necessary.
 * Vendor-specific subclasses of {@link DefaultJdoDialect} are still required for special
 * transaction semantics and more sophisticated exception translation (if needed).
 *
 * <p>In general, it is recommended to derive from {@link DefaultJdoDialect} instead
 * of implementing this interface directly. This allows for inheriting common
 * behavior (present and future) from {@link DefaultJdoDialect}, only overriding
 * specific hooks to plug in concrete vendor-specific behavior.
 *
 * @see JdoTransactionManager#setJdoDialect
 * @see DefaultJdoDialect
 */
public interface JdoDialect {

	//-------------------------------------------------------------------------
	// Hooks for transaction management (used by JdoTransactionManager)
	//-------------------------------------------------------------------------

	/**
	 * Begin the given JDO transaction, applying the semantics specified by the
	 * given Spring transaction definition (in particular, an isolation level
	 * and a timeout). Invoked by JdoTransactionManager on transaction begin.
	 * <p>An implementation can configure the JDO Transaction object and then
	 * invoke {@code begin}, or invoke a special begin method that takes,
	 * for example, an isolation level.
	 * <p>An implementation can also apply read-only flag and isolation level to the
	 * underlying JDBC Connection before beginning the transaction. In that case,
	 * a transaction data object can be returned that holds the previous isolation
	 * level (and possibly other data), to be reset in {@code cleanupTransaction}.
	 * <p>Implementations can also use the Spring transaction name, as exposed by the
	 * passed-in TransactionDefinition, to optimize for specific data access use cases
	 * (effectively using the current transaction name as use case identifier).
	 * @param transaction the JDO transaction to begin
	 * @param definition the Spring transaction definition that defines semantics
	 * @return an arbitrary object that holds transaction data, if any
	 * (to be passed into cleanupTransaction)
	 * @throws JDOException if thrown by JDO methods
	 * @throws SQLException if thrown by JDBC methods
	 * @throws TransactionException in case of invalid arguments
	 * @see #cleanupTransaction
	 * @see javax.jdo.Transaction#begin
	 * @see org.springframework.jdbc.datasource.DataSourceUtils#prepareConnectionForTransaction
	 */
	Object beginTransaction(Transaction transaction, TransactionDefinition definition)
			throws JDOException, SQLException, TransactionException;

	/**
	 * Clean up the transaction via the given transaction data.
	 * Invoked by JdoTransactionManager on transaction cleanup.
	 * <p>An implementation can, for example, reset read-only flag and
	 * isolation level of the underlying JDBC Connection. Furthermore,
	 * an exposed data access use case can be reset here.
	 * @param transactionData arbitrary object that holds transaction data, if any
	 * (as returned by beginTransaction)
	 * @see #beginTransaction
	 * @see org.springframework.jdbc.datasource.DataSourceUtils#resetConnectionAfterTransaction
	 */
	void cleanupTransaction(Object transactionData);

	/**
	 * Retrieve the JDBC Connection that the given JDO PersistenceManager uses underneath,
	 * if accessing a relational database. This method will just get invoked if actually
	 * needing access to the underlying JDBC Connection, usually within an active JDO
	 * transaction (for example, by JdoTransactionManager). The returned handle will
	 * be passed into the {@code releaseJdbcConnection} method when not needed anymore.
	 * <p>Implementations are encouraged to return an unwrapped Connection object, i.e.
	 * the Connection as they got it from the connection pool. This makes it easier for
	 * application code to get at the underlying native JDBC Connection, like an
	 * OracleConnection, which is sometimes necessary for LOB handling etc. We assume
	 * that calling code knows how to properly handle the returned Connection object.
	 * <p>In a simple case where the returned Connection will be auto-closed with the
	 * PersistenceManager or can be released via the Connection object itself, an
	 * implementation can return a SimpleConnectionHandle that just contains the
	 * Connection. If some other object is needed in {@code releaseJdbcConnection},
	 * an implementation should use a special handle that references that other object.
	 * @param pm the current JDO PersistenceManager
	 * @param readOnly whether the Connection is only needed for read-only purposes
	 * @return a handle for the JDBC Connection, to be passed into
	 * {@code releaseJdbcConnection}, or {@code null}
	 * if no JDBC Connection can be retrieved
	 * @throws JDOException if thrown by JDO methods
	 * @throws SQLException if thrown by JDBC methods
	 * @see #releaseJdbcConnection
	 * @see org.springframework.jdbc.datasource.ConnectionHandle#getConnection
	 * @see org.springframework.jdbc.datasource.SimpleConnectionHandle
	 * @see JdoTransactionManager#setDataSource
	 * @see org.springframework.jdbc.support.nativejdbc.NativeJdbcExtractor
	 */
	ConnectionHandle getJdbcConnection(PersistenceManager pm, boolean readOnly)
			throws JDOException, SQLException;

	/**
	 * Release the given JDBC Connection, which has originally been retrieved
	 * via {@code getJdbcConnection}. This should be invoked in any case,
	 * to allow for proper release of the retrieved Connection handle.
	 * <p>An implementation might simply do nothing, if the Connection returned
	 * by {@code getJdbcConnection} will be implicitly closed when the JDO
	 * transaction completes or when the PersistenceManager is closed.
	 * @param conHandle the JDBC Connection handle to release
	 * @param pm the current JDO PersistenceManager
	 * @throws JDOException if thrown by JDO methods
	 * @throws SQLException if thrown by JDBC methods
	 * @see #getJdbcConnection
	 */
	void releaseJdbcConnection(ConnectionHandle conHandle, PersistenceManager pm)
			throws JDOException, SQLException;


	//-----------------------------------------------------------------------------------
	// Hook for exception translation (used by JdoTransactionManager)
	//-----------------------------------------------------------------------------------

	/**
	 * Translate the given JDOException to a corresponding exception from Spring's
	 * generic DataAccessException hierarchy. An implementation should apply
	 * PersistenceManagerFactoryUtils' standard exception translation if can't do
	 * anything more specific.
	 * <p>Of particular importance is the correct translation to
	 * DataIntegrityViolationException, for example on constraint violation.
	 * Unfortunately, standard JDO does not allow for portable detection of this.
	 * <p>Can use a SQLExceptionTranslator for translating underlying SQLExceptions
	 * in a database-specific fashion.
	 * @param ex the JDOException thrown
	 * @return the corresponding DataAccessException (must not be {@code null})
	 * @see JdoTransactionManager#convertJdoAccessException
	 * @see PersistenceManagerFactoryUtils#convertJdoAccessException
	 * @see org.springframework.dao.DataIntegrityViolationException
	 * @see org.springframework.jdbc.support.SQLExceptionTranslator
	 */
	DataAccessException translateException(JDOException ex);

}
