org.springframework.orm.jpa

Interface JpaDialect

All Superinterfaces:

PersistenceExceptionTranslator

All Known Implementing Classes:

DefaultJpaDialect, EclipseLinkJpaDialect, HibernateJpaDialect

public interface JpaDialect
extends PersistenceExceptionTranslator

SPI strategy that encapsulates certain functionality that standard JPA 2.1 does not offer, such as access to the underlying JDBC Connection. This strategy is mainly intended for standalone usage of a JPA provider; most of its functionality is not relevant when running with JTA transactions.

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

Since:

2.0

Author:

Juergen Hoeller, Rod Johnson

See Also:

DefaultJpaDialect, JpaTransactionManager.setJpaDialect(org.springframework.orm.jpa.JpaDialect), JpaVendorAdapter.getJpaDialect(), AbstractEntityManagerFactoryBean.setJpaDialect(org.springframework.orm.jpa.JpaDialect), AbstractEntityManagerFactoryBean.setJpaVendorAdapter(org.springframework.orm.jpa.JpaVendorAdapter)

Method Summary

Modifier and Type	Method and Description
Object	beginTransaction(EntityManager entityManager, TransactionDefinition definition) Begin the given JPA transaction, applying the semantics specified by the given Spring transaction definition (in particular, an isolation level and a timeout).
void	cleanupTransaction(Object transactionData) Clean up the transaction via the given transaction data.
ConnectionHandle	getJdbcConnection(EntityManager entityManager, boolean readOnly) Retrieve the JDBC Connection that the given JPA EntityManager uses underneath, if accessing a relational database.
Object	prepareTransaction(EntityManager entityManager, boolean readOnly, String name) Prepare a JPA transaction, applying the specified semantics.
void	releaseJdbcConnection(ConnectionHandle conHandle, EntityManager entityManager) Release the given JDBC Connection, which has originally been retrieved via getJdbcConnection.

Methods inherited from interface org.springframework.dao.support.PersistenceExceptionTranslator

translateExceptionIfPossible

Method Detail

beginTransaction

@Nullable
Object beginTransaction(EntityManager entityManager,
                                  TransactionDefinition definition)
                           throws PersistenceException,
                                  SQLException,
                                  TransactionException

Begin the given JPA transaction, applying the semantics specified by the given Spring transaction definition (in particular, an isolation level and a timeout). Called by JpaTransactionManager on transaction begin.

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

An implementation can apply the read-only flag as flush mode. In that case, a transaction data object can be returned that holds the previous flush mode (and possibly other data), to be reset in cleanupTransaction. It may also apply the read-only flag and isolation level to the underlying JDBC Connection before beginning the transaction.

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).

This method also allows for exposing savepoint capabilities if supported by the persistence provider, through returning an Object that implements Spring's SavepointManager interface. JpaTransactionManager will use this capability if needed.

Parameters:

entityManager - the EntityManager to begin a JPA transaction on

definition - the Spring transaction definition that defines semantics

Returns:

an arbitrary object that holds transaction data, if any (to be passed into cleanupTransaction(java.lang.Object)). May implement the SavepointManager interface.

Throws:

PersistenceException - if thrown by JPA methods

SQLException - if thrown by JDBC methods

TransactionException - in case of invalid arguments

See Also:

cleanupTransaction(java.lang.Object), EntityTransaction.begin(), DataSourceUtils.prepareConnectionForTransaction(java.sql.Connection, org.springframework.transaction.TransactionDefinition)

prepareTransaction

@Nullable
Object prepareTransaction(EntityManager entityManager,
                                    boolean readOnly,
                                    @Nullable
                                    String name)
                             throws PersistenceException

Prepare a JPA transaction, applying the specified semantics. Called by EntityManagerFactoryUtils when enlisting an EntityManager in a JTA transaction or a locally joined transaction (e.g. after upgrading an unsynchronized EntityManager to a synchronized one).

An implementation can apply the read-only flag as flush mode. In that case, a transaction data object can be returned that holds the previous flush mode (and possibly other data), to be reset in cleanupTransaction.

Implementations can also use the Spring transaction name to optimize for specific data access use cases (effectively using the current transaction name as use case identifier).

Parameters:

entityManager - the EntityManager to begin a JPA transaction on

readOnly - whether the transaction is supposed to be read-only

name - the name of the transaction (if any)

Returns:

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

Throws:

PersistenceException - if thrown by JPA methods

See Also:

cleanupTransaction(java.lang.Object)

cleanupTransaction

void cleanupTransaction(@Nullable
                        Object transactionData)

Clean up the transaction via the given transaction data. Called by JpaTransactionManager and EntityManagerFactoryUtils 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 or prepareTransaction)

See Also:

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

getJdbcConnection

@Nullable
ConnectionHandle getJdbcConnection(EntityManager entityManager,
                                             boolean readOnly)
                                      throws PersistenceException,
                                             SQLException

Retrieve the JDBC Connection that the given JPA EntityManager 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 JPA transaction (for example, by JpaTransactionManager). The returned handle will be passed into the releaseJdbcConnection method when not needed anymore.

This strategy is necessary as JPA does not provide a standard way to retrieve the underlying JDBC Connection (due to the fact that a JPA implementation might not work with a relational database at all).

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 EntityManager 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:

entityManager - the current JPA EntityManager

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

Returns:

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

Throws:

PersistenceException - if thrown by JPA methods

SQLException - if thrown by JDBC methods

See Also:

releaseJdbcConnection(org.springframework.jdbc.datasource.ConnectionHandle, javax.persistence.EntityManager), ConnectionHandle.getConnection(), SimpleConnectionHandle, JpaTransactionManager.setDataSource(javax.sql.DataSource)

releaseJdbcConnection

void releaseJdbcConnection(ConnectionHandle conHandle,
                           EntityManager entityManager)
                    throws PersistenceException,
                           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 JPA transaction completes or when the EntityManager is closed.

Parameters:

conHandle - the JDBC Connection handle to release

entityManager - the current JPA EntityManager

Throws:

PersistenceException - if thrown by JPA methods

SQLException - if thrown by JDBC methods

See Also:

getJdbcConnection(javax.persistence.EntityManager, boolean)