| org.odmg.Transaction
All known Subclasses: org.apache.ojb.odmg.TransactionImpl,
| Transaction | | public interface Transaction (Code) | | This interfaces provides the operations necessary to perform database transactions.
All access, creation, and modification of persistent objects and their fields
must be done within a transaction. Before performing any database operations,
a thread must explicitly create a transaction object or associate itself with
an existing transaction object (by calling join),
and that transaction must be open (through a call to begin).
All subsequent operations by the thread, including reads, writes, and lock
acquisitions, are done under the thread’s current transaction.
A thread may only operate on its current transaction. For example,
a TransactionNotInProgressException is thrown if a thread attempts
to begin, commit, checkpoint, or abort a transaction prior to joining itself
to that transaction.
A transaction is either open or closed. A transaction is open if a call
has been made to begin, but no call has been made to commit or
abort. Once commit or abort is called,
the transaction is closed. The method isOpen can be called to
determine the state of the transaction.
Read locks are implicitly obtained on objects as they are accessed.
Write locks are implicitly obtained as objects are modified.
Transaction objects are transient, they cannot be stored in the database.
author:
David Jordan (as Java Editor of the Object Data Management Group)
version:
ODMG 3.0
See Also: TransactionNotInProgressException |
| Field Summary | |
| final public static int | READ
Read lock mode. | | final public static int | UPGRADE
Upgrade lock mode. | | final public static int | WRITE
Write lock mode. |
| Method Summary | |
| public void | abort()
Abort and close the transaction. | | public void | begin()
Start a transaction.
Calling begin multiple times on the same transaction object,
without an intervening call to commit or abort,
causes the exception TransactionInProgressException to be thrown
on the second and subsequent calls. | | public void | checkpoint()
Commit the transaction, but reopen the transaction, retaining all locks. | | public void | commit()
Commit and close the transaction.
Calling commit commits to the database all persistent object
modifications within the transaction and releases any locks held by the transaction.
A persistent object modification is an update of any field of an existing
persistent object, or an update or creation of a new named object in the database.
If a persistent object modification results in a reference from an existing
persistent object to a transient object, the transient object is moved to the
database, and all references to it updated accordingly. | | public boolean | isOpen()
Determine whether the transaction is open or not. | | public void | join()
Attach the caller's thread to this Transaction and detach the thread
from any former Transaction the thread may have been associated with. | | public void | leave()
Detach the caller's thread from this Transaction, but do not attach
the thread to another Transaction. | | public void | lock(Object obj, int lockMode)
Upgrade the lock on the given object to the given lock mode.
The call has no effect if the object's current lock is already at or above
that level of lock mode.
Parameters:
obj - The object to acquire a lock on.
Parameters:
lockMode - The lock mode to acquire. | | public boolean | tryLock(Object obj, int lockMode)
Upgrade the lock on the given object to the given lock mode.
Method tryLock is the same as lock except it returns
a boolean indicating whether the lock was granted instead of generating an exception.
Parameters:
obj - The object to acquire a lock on.
Parameters:
lockMode - The lock mode to acquire. |
| READ | | final public static int READ(Code) | | Read lock mode.
|
| UPGRADE | | final public static int UPGRADE(Code) | | Upgrade lock mode.
|
| WRITE | | final public static int WRITE(Code) | | Write lock mode.
|
| abort | | public void abort()(Code) | | Abort and close the transaction.
Calling abort abandons all persistent object modifications and releases the
associated locks.
Aborting a transaction does not restore the state of modified transient objects
|
| begin | | public void begin()(Code) | | Start a transaction.
Calling begin multiple times on the same transaction object,
without an intervening call to commit or abort,
causes the exception TransactionInProgressException to be thrown
on the second and subsequent calls. Operations executed before a transaction
has been opened, or before reopening after a transaction is aborted or committed,
have undefined results;
these may throw a TransactionNotInProgressException exception.
|
| checkpoint | | public void checkpoint()(Code) | | Commit the transaction, but reopen the transaction, retaining all locks.
Calling checkpoint commits persistent object modifications made
within the transaction since the last checkpoint to the database.
The transaction retains all locks it held on those objects at the time the
checkpoint was invoked.
|
| commit | | public void commit()(Code) | | Commit and close the transaction.
Calling commit commits to the database all persistent object
modifications within the transaction and releases any locks held by the transaction.
A persistent object modification is an update of any field of an existing
persistent object, or an update or creation of a new named object in the database.
If a persistent object modification results in a reference from an existing
persistent object to a transient object, the transient object is moved to the
database, and all references to it updated accordingly. Note that the act of
moving a transient object to the database may create still more persistent
references to transient objects, so its referents must be examined and moved as well.
This process continues until the database contains no references to transient objects,
a condition that is guaranteed as part of transaction commit.
Committing a transaction does not remove from memory transient objects created
during the transaction
|
| isOpen | | public boolean isOpen()(Code) | | Determine whether the transaction is open or not.
A transaction is open if a call has been made to begin,
but a subsequent call to either commit or abort
has not been made.
True if the transaction is open, otherwise false. |
| join | | public void join()(Code) | | Attach the caller's thread to this Transaction and detach the thread
from any former Transaction the thread may have been associated with.
|
| leave | | public void leave()(Code) | | Detach the caller's thread from this Transaction, but do not attach
the thread to another Transaction.
|
| lock | | public void lock(Object obj, int lockMode) throws LockNotGrantedException(Code) | | Upgrade the lock on the given object to the given lock mode.
The call has no effect if the object's current lock is already at or above
that level of lock mode.
Parameters:
obj - The object to acquire a lock on.
Parameters:
lockMode - The lock mode to acquire. The lock modes are READ,UPGRADE, and WRITE.
exception:
LockNotGrantedException - Is thrown if the given lock mode could not be acquired. |
| tryLock | | public boolean tryLock(Object obj, int lockMode)(Code) | | Upgrade the lock on the given object to the given lock mode.
Method tryLock is the same as lock except it returns
a boolean indicating whether the lock was granted instead of generating an exception.
Parameters:
obj - The object to acquire a lock on.
Parameters:
lockMode - The lock mode to acquire. The lock modes are READ,UPGRADE, and WRITE. True if the lock has been acquired, otherwise false. |
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