org.eclipse.persistence.config
Class ExclusiveConnectionMode
java.lang.Object
org.eclipse.persistence.config.ExclusiveConnectionMode
public class ExclusiveConnectionMode
- extends java.lang.Object
This property could be specified while creating either EntityManagerFactory
(createEntityManagerFactory or persistence.xml)
or EntityManager (createEntityManager); the latter overrides the former.
The "isolated case" mentioned below is the case of some (or all) entities requiring isolated cache.
That could be achieved either by specifying the property for one or more entities:
eclipselink.cache.shared.Employee -> "false"
or for all entities:
eclipselink.cache.shared.default -> "false"
Note that this property(es) could be specified only on persistence unit level (cannot be passed to createEntityManager method).
JPA persistence property Usage:
properties.add(PersistenceUnitProperties.EXCLUSIVE_CONNECTION_MODE, ExclusiveConnectionMode.Isolated);
Values are case-insensitive.
"" could be used instead of default value ExclusiveConnectionMode.DEFAULT.
- See Also:
PersistenceUnitProperties
|
Field Summary |
static java.lang.String |
Always
The value causes creation of ExclusiveIsolatedClientSession
in both isolated and non-isolated cases. |
static java.lang.String |
DEFAULT
|
static java.lang.String |
Isolated
The value causes creation of
ExclusiveIsolatedClientSession in isolated case
and throws exception otherwise. |
static java.lang.String |
Transactional
The value causes creation of
IsolatedClientSession in isolated case
and ClientSession otherwise. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Transactional
public static final java.lang.String Transactional
- The value causes creation of
IsolatedClientSession in isolated case
and ClientSession otherwise.
Connection is kept exclusive for the duration of Eclipselink transaction.
Inside Eclipselink transaction all writes and reads performed through the exclusive connection.
Outside Eclipselink transaction a new connection is acquired from connection pool
for each read and released back immediately after the query is executed.
Note that Eclipselink transaction usually starts later then JTA transaction does,
or entityManager.beginTransaction method is called: Eclipselink usually waits until
it's about to perform a query that potentially alters data base's state to start
Exclipselink transaction. That reflects in connection usage in Transactional mode.
Example:
// Eclipselink transaction is not started yet - readQuery1 acquires and immediately releases connection.
readQuery1.getResultList();
entityManager.getTransaction().begin();
// Eclipselink transaction still not started yet - readQuery2 acquires and immediately releases connection.
readQuery2.getResultList();
entityManager.persist(new Employee());
// Eclipselink transaction is not started yet - readQuery3 acquires and immediately releases connection.
readQuery3.getResultList();
entityManager.flush();
// Before the flushing is performed Exclipselink transaction is started:
// connection is acquired that will be kept until the end of transaction and used for all reads and writes.
readQuery4.getResultList();
entityManager.commit();
// Eclipselink transaction is completed, the connection used by Eclipselink transaction is released;
// readQuery5 acquires and immediately releases connection.
readQuery5.getResultList();
There's a way to force beginning of Eclipselink transaction right before executing the first query after em.getTransaction().begin():
"eclipselink.transaction.join-existing" -> true.
In the example that setting would force Exclipselink transaction top begin right before readQuery2 is executed
and therefore cause execution of readQuery2 and readQuery3 through the exclusive connection
(of course the same connection would be used by readQuery4 and flush, too).
However this approach could hardly be recommended:
none of the objects read after Eclipselink transaction begins
get into the shared cache unless altered therefore seriously reducing benefits of Eclipselink shared cache.
- See Also:
- Constant Field Values
Isolated
public static final java.lang.String Isolated
- The value causes creation of
ExclusiveIsolatedClientSession in isolated case
and throws exception otherwise.
Connection is kept exclusive for the whole lifetime of the owning EntityManager.
Inside Eclipselink transaction all writes and reads performed through the exclusive connection.
Outside Eclipelink transaction only isolated entities are read through the exclusive connection;
for non isolated entities a new connection is acquired from connection pool
for each read and released back immediately after the query is executed.
In the example presented above all five readQueries
would read isolated entity through the exclusive connection,
however non-isolated entity would be read the same as in Transactional mode.
- See Also:
- Constant Field Values
Always
public static final java.lang.String Always
- The value causes creation of ExclusiveIsolatedClientSession
in both isolated and non-isolated cases.
Connection is kept exclusive for the whole lifetime of the owning EntityManager.
All writes and reads performed through the exclusive connection.
In the example presented above all five readQueries
would read all entity through the exclusive connection.
Note that though all entities use the exclusive connection
only isolated entities use isolated cache; non-isolated entities use shared cache.
- See Also:
- Constant Field Values
DEFAULT
public static final java.lang.String DEFAULT
- See Also:
- Constant Field Values
ExclusiveConnectionMode
public ExclusiveConnectionMode()