org.springframework.orm.toplink
Class SessionReadCallback

java.lang.Object
  org.springframework.orm.toplink.SessionReadCallback

All Implemented Interfaces:

TopLinkCallback

public abstract class SessionReadCallback
extends Object
implements TopLinkCallback

Convenient abstract implementation of the TopLinkCallback interface, exposing either the plain TopLink Session or the TopLink UnitOfWork (which extends the Session interface) to code that reads persistent objects.

Exposes the UnitOfWork if there is an active one (that is, if we're running within a non-read-only transaction); else exposes the Session itself. This allows to modify returned objects within a transaction, which is often desired, while the same code will return shared cache objects if running outside a transaction.

If "enforceReadOnly" is demanded, the callback will always expose the Session itself, avoiding the UnitOfWork overhead in any case.

Since:

1.2

Author:

Juergen Hoeller

See Also:

Session.getActiveUnitOfWork(), readFromSession(oracle.toplink.sessions.Session)

Constructor Summary

SessionReadCallback()
Create a new SessionReadCallback, not enforcing read-only objects.

SessionReadCallback(boolean enforceReadOnly)
Create a new SessionReadCallback, enforcing read-only objects if demanded.

Method Summary

Object	doInTopLink(oracle.toplink.sessions.Session session) Determines the Session to work on (either the active UnitOfWork or the plain Session) and delegates to readFromSession.
protected abstract Object	readFromSession(oracle.toplink.sessions.Session session) Called with a Session to work on, either the active UnitOfWork or the plain Session (as determined by the transaction status).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SessionReadCallback

public SessionReadCallback()

Create a new SessionReadCallback, not enforcing read-only objects.

SessionReadCallback

public SessionReadCallback(boolean enforceReadOnly)

Create a new SessionReadCallback, enforcing read-only objects if demanded.

Parameters:

enforceReadOnly - whether to enforce returning read-only objects, even if running within a non-read-only transaction

Method Detail

doInTopLink

public final Object doInTopLink(oracle.toplink.sessions.Session session)
                         throws oracle.toplink.exceptions.TopLinkException

Determines the Session to work on (either the active UnitOfWork or the plain Session) and delegates to readFromSession.

Specified by:

doInTopLink in interface TopLinkCallback

Parameters:

session - active TopLink Session

Returns:

a result object, or null if none

Throws:

oracle.toplink.exceptions.TopLinkException - if thrown by the TopLink API

See Also:

readFromSession(oracle.toplink.sessions.Session)

readFromSession

protected abstract Object readFromSession(oracle.toplink.sessions.Session session)
                                   throws oracle.toplink.exceptions.TopLinkException

Called with a Session to work on, either the active UnitOfWork or the plain Session (as determined by the transaction status).

Parameters:

session - the TopLink Session to perform read operations on

Returns:

a result object, or null if none

Throws:

oracle.toplink.exceptions.TopLinkException - in case of TopLink errors