org.springframework.orm.jdo

Interface JdoDialect

All Known Implementing Classes:

DefaultJdoDialect

public interface JdoDialect

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 JPOX, Kodo, Lido, Versant Open Access.

JDO 3.0 defines standard ways for most of the functionality covered here. Hence, Spring's DefaultJdoDialect uses the corresponding JDO 3.0 methods by default, to be overridden in a vendor-specific fashion if necessary. Vendor-specific subclasses of DefaultJdoDialect are still required for special transaction semantics and more sophisticated exception translation (if needed).

In general, it is recommended to derive from DefaultJdoDialect instead of implementing this interface directly. This allows for inheriting common behavior (present and future) from DefaultJdoDialect, only overriding specific hooks to plug in concrete vendor-specific behavior.

Since:

02.11.2003

Author:

Juergen Hoeller

See Also:

JdoTransactionManager.setJdoDialect(org.springframework.orm.jdo.JdoDialect), DefaultJdoDialect

Method Summary

Modifier and Type	Method and Description
java.lang.Object	beginTransaction(Transaction transaction, TransactionDefinition definition) Begin the given JDO transaction, applying the semantics specified by the given Spring transaction definition (in particular, an isolation level and a timeout).
void	cleanupTransaction(java.lang.Object transactionData) Clean up the transaction via the given transaction data.
ConnectionHandle	getJdbcConnection(PersistenceManager pm, boolean readOnly) Retrieve the JDBC Connection that the given JDO PersistenceManager uses underneath, if accessing a relational database.
void	releaseJdbcConnection(ConnectionHandle conHandle, PersistenceManager pm) Release the given JDBC Connection, which has originally been retrieved via getJdbcConnection.
DataAccessException	translateException(JDOException ex) Translate the given JDOException to a corresponding exception from Spring's generic DataAccessException hierarchy.

Method Detail

beginTransaction

java.lang.Object beginTransaction(Transaction transaction,
                                  TransactionDefinition definition)
                           throws JDOException,
                                  java.sql.SQLException,
                                  TransactionException

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.

An implementation can configure the JDO Transaction object and then invoke begin, or invoke a special begin method that takes, for example, an isolation level.

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 cleanupTransaction.

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).

Parameters:

transaction - the JDO transaction to begin

definition - the Spring transaction definition that defines semantics

Returns:

an arbitrary object that holds transaction data, if any (to be passed into cleanupTransaction)

Throws:

JDOException - if thrown by JDO methods

java.sql.SQLException - if thrown by JDBC methods

TransactionException - in case of invalid arguments

See Also:

cleanupTransaction(java.lang.Object), javax.jdo.Transaction#begin, DataSourceUtils.prepareConnectionForTransaction(java.sql.Connection, org.springframework.transaction.TransactionDefinition)

cleanupTransaction

void cleanupTransaction(java.lang.Object transactionData)

Clean up the transaction via the given transaction data. Invoked by JdoTransactionManager on transaction cleanup.

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.

Parameters:

transactionData - arbitrary object that holds transaction data, if any (as returned by beginTransaction)

See Also:

beginTransaction(Transaction, org.springframework.transaction.TransactionDefinition), DataSourceUtils.resetConnectionAfterTransaction(java.sql.Connection, java.lang.Integer)

getJdbcConnection

ConnectionHandle getJdbcConnection(PersistenceManager pm,
                                   boolean readOnly)
                            throws JDOException,
                                   java.sql.SQLException

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 releaseJdbcConnection method when not needed anymore.

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.

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 releaseJdbcConnection, an implementation should use a special handle that references that other object.

Parameters:

pm - the current JDO PersistenceManager

readOnly - whether the Connection is only needed for read-only purposes

Returns:

a handle for the JDBC Connection, to be passed into releaseJdbcConnection, or null if no JDBC Connection can be retrieved

Throws:

JDOException - if thrown by JDO methods

java.sql.SQLException - if thrown by JDBC methods

See Also:

releaseJdbcConnection(org.springframework.jdbc.datasource.ConnectionHandle, PersistenceManager), ConnectionHandle.getConnection(), SimpleConnectionHandle, JdoTransactionManager.setDataSource(javax.sql.DataSource), NativeJdbcExtractor

releaseJdbcConnection

void releaseJdbcConnection(ConnectionHandle conHandle,
                           PersistenceManager pm)
                    throws JDOException,
                           java.sql.SQLException

Release the given JDBC Connection, which has originally been retrieved via getJdbcConnection. This should be invoked in any case, to allow for proper release of the retrieved Connection handle.

An implementation might simply do nothing, if the Connection returned by getJdbcConnection will be implicitly closed when the JDO transaction completes or when the PersistenceManager is closed.

Parameters:

conHandle - the JDBC Connection handle to release

pm - the current JDO PersistenceManager

Throws:

JDOException - if thrown by JDO methods

java.sql.SQLException - if thrown by JDBC methods

See Also:

getJdbcConnection(PersistenceManager, boolean)

translateException

DataAccessException translateException(JDOException ex)

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.

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.

Can use a SQLExceptionTranslator for translating underlying SQLExceptions in a database-specific fashion.

Parameters:

ex - the JDOException thrown

Returns:

the corresponding DataAccessException (must not be null)

See Also:

JdoTransactionManager.convertJdoAccessException(JDOException), PersistenceManagerFactoryUtils.convertJdoAccessException(JDOException), DataIntegrityViolationException, SQLExceptionTranslator