org.apache.ojb.odmg.locking
Class ReadUncommittedStrategy

java.lang.Object
  org.apache.ojb.odmg.locking.AbstractLockStrategy
      org.apache.ojb.odmg.locking.ReadUncommittedStrategy

All Implemented Interfaces:

LockStrategy

public class ReadUncommittedStrategy
extends AbstractLockStrategy

The implementation of the Uncommited Reads Locking strategy. This strategy is the loosest of them all. It says you shouldn't need to get any Read locks whatsoever, but since it will probably try to get them, it will always give it to them. Locks are obtained on modifications to the database and held until end of transaction (EOT). Reading from the database does not involve any locking. Allows: Dirty Reads Non-Repeatable Reads Phantom Reads

Author:

Thomas Mahler & David Dixon-Peugh

Field Summary

Fields inherited from class org.apache.ojb.odmg.locking.AbstractLockStrategy

DEFAULT_LOCK_TIMEOUT

Constructor Summary

ReadUncommittedStrategy()

Method Summary

boolean	checkRead(TransactionImpl tx, Object obj) checks whether the specified Object obj is read-locked by Transaction tx.
boolean	checkWrite(TransactionImpl tx, Object obj) checks whether the specified Object obj is write-locked by Transaction tx.
boolean	readLock(TransactionImpl tx, Object obj) acquire a read lock on Object obj for Transaction tx.
boolean	releaseLock(TransactionImpl tx, Object obj) release a lock on Object obj for Transaction tx.
boolean	upgradeLock(TransactionImpl tx, Object obj) acquire a lock upgrade (from read to write) lock on Object obj for Transaction tx.
boolean	writeLock(TransactionImpl tx, Object obj) acquire a write lock on Object obj for Transaction tx.

Methods inherited from class org.apache.ojb.odmg.locking.AbstractLockStrategy

addReader, getReaders, getWriter, hasReadLock, removeReader, removeWriter, setWriter, upgradeLock

Methods inherited from class java.lang.Object

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

Constructor Detail

ReadUncommittedStrategy

public ReadUncommittedStrategy()

Method Detail

readLock

public boolean readLock(TransactionImpl tx,
                        Object obj)

acquire a read lock on Object obj for Transaction tx.

Parameters:

tx - the transaction requesting the lock

obj - the Object to be locked

Returns:

true if successful, else false When we read Uncommitted, we don't care about Reader locks

writeLock

public boolean writeLock(TransactionImpl tx,
                         Object obj)

acquire a write lock on Object obj for Transaction tx.

Parameters:

tx - the transaction requesting the lock

obj - the Object to be locked

Returns:

true if successful, else false

upgradeLock

public boolean upgradeLock(TransactionImpl tx,
                           Object obj)

acquire a lock upgrade (from read to write) lock on Object obj for Transaction tx.

Parameters:

tx - the transaction requesting the lock

obj - the Object to be locked

Returns:

true if successful, else false

releaseLock

public boolean releaseLock(TransactionImpl tx,
                           Object obj)

release a lock on Object obj for Transaction tx.

Parameters:

tx - the transaction releasing the lock

obj - the Object to be unlocked

Returns:

true if successful, else false

checkRead

public boolean checkRead(TransactionImpl tx,
                         Object obj)

checks whether the specified Object obj is read-locked by Transaction tx.

Parameters:

tx - the transaction

obj - the Object to be checked

Returns:

true if lock exists, else false

checkWrite

public boolean checkWrite(TransactionImpl tx,
                          Object obj)

checks whether the specified Object obj is write-locked by Transaction tx.

Parameters:

tx - the transaction

obj - the Object to be checked

Returns:

true if lock exists, else false