com.goldencode.p2j.persist.lock

Class RecordLockContext.Perm.LockState

java.lang.Object

com.goldencode.p2j.persist.lock.RecordLockContext.Perm.LockState

Enclosing class:

RecordLockContext.Perm

private final class RecordLockContext.Perm.LockState
extends java.lang.Object

The lock state of a particular record, which includes its current lock type, its unique identifier, and the set of buffers which share access to the backing lock.

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.List<RecordBuffer>	buffers Buffers who share this lock state
private LockType	currentType Lock type currently assigned to the record
private RecordIdentifier<java.lang.String>	ident Database record whose lock state is being tracked

Constructor Summary

Constructors

Constructor and Description
LockState(RecordIdentifier<java.lang.String> ident) Constructor which queries current lock type for a record from the lock manager.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object o) Override parent's implementation of equality.
(package private) LockType	getCurrentType() Get the current lock type.
(package private) RecordIdentifier<java.lang.String>	getIdentifier() Get record's unique identifier.
int	hashCode() Override parent's implementation to be consistent with equals(Object).
(package private) boolean	registerBuffer(RecordBuffer buffer) Register a record buffer which shares access to the record's current lock.
(package private) void	relinquish(LockType requestedType) Attempt to relinquish the lock represented by this object, releasing or downgrading it if possible.
(package private) void	setCurrentType(LockType currentType) Set the current lock type.
(package private) void	transactionEnded() Process any pending lock change which has been deferred during the most recent application level transaction.
private void	updateLock(LockType lockType) Attempt to update the current lock on the record immediately.

Methods inherited from class java.lang.Object

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

Field Detail

ident

private final RecordIdentifier<java.lang.String> ident

Database record whose lock state is being tracked

buffers

private final java.util.List<RecordBuffer> buffers

Buffers who share this lock state

currentType

private LockType currentType

Lock type currently assigned to the record

Constructor Detail

LockState

LockState(RecordIdentifier<java.lang.String> ident)

Constructor which queries current lock type for a record from the lock manager.

Parameters:

ident - Unique identifier for the database record whose lock type is to be queried from the lock manager.

Method Detail

hashCode

public int hashCode()

Override parent's implementation to be consistent with equals(Object).

Overrides:

hashCode in class java.lang.Object

Returns:

Hash code for this object.

equals

public boolean equals(java.lang.Object o)

Override parent's implementation of equality. Two instances of this class are considered equal if they represent the same lockable resource, regardless of the other internal state.

Overrides:

equals in class java.lang.Object

Parameters:

o - Another instance of this class to test for equality with this instance.

Returns:

true if this object and the given instance have the same record identifier, else false.

registerBuffer

boolean registerBuffer(RecordBuffer buffer)

Register a record buffer which shares access to the record's current lock. Deregistration occurs implicitly when this buffer no longer pins the lock.

Parameters:

buffer - Record buffer to be registered.

Returns:

true if the buffer was added; false if it was previously registered.

getIdentifier

RecordIdentifier<java.lang.String> getIdentifier()

Get record's unique identifier.

Returns:

Unique identifier.

getCurrentType

LockType getCurrentType()

Get the current lock type.

Returns:

Current lock type.

setCurrentType

void setCurrentType(LockType currentType)

Set the current lock type. This will always set the current type to a non-no-wait variant.

Parameters:

currentType - Current type to be set. Only the category is used (i.e., NONE, SHARE, EXCLUSIVE); the no-wait-"ness" of the lock type is discarded.

transactionEnded

void transactionEnded()
               throws LockUnavailableException

Process any pending lock change which has been deferred during the most recent application level transaction. Specifically, release or downgrade a lock according to how it is pinned by all record buffers which reference it.

Throws:

LockUnavailableException - never, since we are never acquiring a more restrictive lock, only downgrading or releasing.

relinquish

void relinquish(LockType requestedType)
         throws LockUnavailableException

Attempt to relinquish the lock represented by this object, releasing or downgrading it if possible. A change is only possible outside a transaction, and then only to the most restrictive lock pinned by any buffer sharing the communal lock.

Parameters:

requestedType - NONE or SHARE only (it doesn't make sense to downgrade to EXCLUSIVE).

Throws:

java.lang.IllegalArgumentException - if an EXCLUSIVE lock is requested.

LockUnavailableException - never, since we never request a no-wait lock here.

updateLock

private void updateLock(LockType lockType)
                 throws LockUnavailableException

Attempt to update the current lock on the record immediately.

Parameters:

lockType - Requested lock type. If NONE, this object will be removed from the map of lock states by identifier.

Throws:

LockUnavailableException - never.