com.arjuna.ats.internal.arjuna.objectstore

Class ShadowingStore

java.lang.Object

com.arjuna.ats.arjuna.objectstore.ObjectStore

com.arjuna.ats.internal.arjuna.objectstore.FileSystemStore

com.arjuna.ats.internal.arjuna.objectstore.ShadowingStore

All Implemented Interfaces:

BaseStore, ObjectStoreAPI, ParticipantStore, RecoveryStore, TxLog

Direct Known Subclasses:

ShadowNoFileLockStore

public class ShadowingStore
extends FileSystemStore

A shadowing file store implementation. Each version of the object's state is maintained in a separate file. So, the original is stored in one file, and the shadow (the updated state) is stored in another. When the transaction commits, the shadow is made the original. If the transaction rolls back then the shadow is simply removed from the object store.

Since:

1.0

Version:

$Id: ShadowingStore.java 2342 2006-03-30 13:06:17Z $

Author:

Mark Little (mark@arjuna.com)

Field Summary

Fields

Modifier and Type	Field and Description
static char	HIDDINGCHAR
static char	SHADOWCHAR

Fields inherited from class com.arjuna.ats.internal.arjuna.objectstore.FileSystemStore

doSync, scanZeroLengthFiles, syncWrites

Fields inherited from class com.arjuna.ats.arjuna.objectstore.ObjectStore

_objectStoreRoot, shareStatus

Constructor Summary

Constructors

Constructor and Description
ShadowingStore(ObjectStoreEnvironmentBean objectStoreEnvironmentBean)

Method Summary

Modifier and Type	Method and Description
boolean	commit_state(Uid objUid, String tName) Commit a previous write_state operation which was made with the SHADOW StateType argument.
int	currentState(Uid objUid, String tName)
protected String	genPathName(Uid objUid, String tName, int ft)
boolean	hide_state(Uid objUid, String tName) Hide/reveal an object regardless of state.
protected InputObjectState	read_state(Uid objUid, String tName, int ft)
protected boolean	remove_state(Uid objUid, String name, int ft)
boolean	reveal_state(Uid objUid, String tName) Reveal a hidden object's state.
protected String	revealedId(String name) Given a type id which is possibly hidden (e.g., has a ! at the end), make it a valid Uid so we can return it.
protected boolean	write_state(Uid objUid, String tName, OutputObjectState state, int ft) write_state saves the ObjectState in a file named by the type and Uid of the ObjectState.

Methods inherited from class com.arjuna.ats.internal.arjuna.objectstore.FileSystemStore

addToCache, allObjUids, allTypes, allTypes, closeAndUnlock, createHierarchy, exists, getStoreName, lock, openAndLock, read_committed, read_uncommitted, remove_committed, remove_uncommitted, removeFromCache, removeFromCache, renameFromTo, supressEntry, synchronousWrites, truncate, unlock, write_committed, write_uncommitted

Methods inherited from class com.arjuna.ats.arjuna.objectstore.ObjectStore

allObjUids, fullCommitNeeded, initialise, isType, locateStore, shareState, start, stop, storeDir, storeRoot, sync

Methods inherited from class java.lang.Object

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

Field Detail

HIDDINGCHAR

public static final char HIDDINGCHAR

See Also:

Constant Field Values

SHADOWCHAR

public static final char SHADOWCHAR

See Also:

Constant Field Values

Constructor Detail

ShadowingStore

public ShadowingStore(ObjectStoreEnvironmentBean objectStoreEnvironmentBean)
               throws ObjectStoreException

Throws:

ObjectStoreException

Method Detail

currentState

public int currentState(Uid objUid,
                        String tName)
                 throws ObjectStoreException

Parameters:

objUid - The object to query.

tName - The type of the object to query.

Returns:

current state of object. Assumes that genPathName allocates enough extra space to allow extra chars to be added. State search is ordered OS_SHADOW, OS_UNCOMMITTED_HIDDEN, OS_ORIGINAL, OS_COMMITTED_HIDDEN.

Throws:

ObjectStoreException

commit_state

public boolean commit_state(Uid objUid,
                            String tName)
                     throws ObjectStoreException

Commit a previous write_state operation which was made with the SHADOW StateType argument. This is achieved by renaming the shadow and removing the hidden version.

Parameters:

objUid - The object to work on.

tName - The type of the object to work on.

Returns:

true if no errors occurred, false otherwise.

Throws:

ObjectStoreException

hide_state

public boolean hide_state(Uid objUid,
                          String tName)
                   throws ObjectStoreException

Hide/reveal an object regardless of state. Hidden objects cannot be read but they can be written (Crash recovery needs this).

Parameters:

objUid - The object to work on.

tName - The type of the object to work on.

Returns:

true if no errors occurred, false otherwise.

Throws:

ObjectStoreException

reveal_state

public boolean reveal_state(Uid objUid,
                            String tName)
                     throws ObjectStoreException

Description copied from interface: RecoveryStore

Reveal a hidden object's state.

Parameters:

objUid - The object to work on.

tName - The type of the object to work on.

Returns:

true if no errors occurred, false otherwise.

Throws:

ObjectStoreException

genPathName

protected String genPathName(Uid objUid,
                             String tName,
                             int ft)
                      throws ObjectStoreException

Overrides:

genPathName in class FileSystemStore

Returns:

the file name for the state of the object identified by the Uid and TypeName. If the StateType argument is OS_SHADOW then the Uid part of the name includes # characters. Builds on lower level genPathName which allocates enough slop to accomodate the extra chars.

Throws:

ObjectStoreException

revealedId

protected String revealedId(String name)

Description copied from class: ObjectStore

Given a type id which is possibly hidden (e.g., has a ! at the end), make it a valid Uid so we can return it.

Overrides:

revealedId in class ObjectStore

read_state

protected InputObjectState read_state(Uid objUid,
                                      String tName,
                                      int ft)
                               throws ObjectStoreException

Specified by:

read_state in class FileSystemStore

Throws:

ObjectStoreException

remove_state

protected boolean remove_state(Uid objUid,
                               String name,
                               int ft)
                        throws ObjectStoreException

Specified by:

remove_state in class FileSystemStore

Throws:

ObjectStoreException

write_state

protected boolean write_state(Uid objUid,
                              String tName,
                              OutputObjectState state,
                              int ft)
                       throws ObjectStoreException

write_state saves the ObjectState in a file named by the type and Uid of the ObjectState. If the second argument is SHADOW, then the file name is different so that a subsequent commit_state invocation will rename the file.

Specified by:

write_state in class FileSystemStore

Throws:

ObjectStoreException