net.sf.farrago.db
Class FarragoDbSingleton

java.lang.Object
  org.eigenbase.util.CompoundClosableAllocation
      net.sf.farrago.util.FarragoCompoundAllocation
          net.sf.farrago.db.FarragoDbSingleton

All Implemented Interfaces:

FarragoAllocation, FarragoAllocationOwner, ClosableAllocation, ClosableAllocationOwner

Direct Known Subclasses:

FarragoDatabase

public abstract class FarragoDbSingleton
extends FarragoCompoundAllocation

FarragoDbSingleton manages a singleton instance of FarragoDatabase. It is reference-counted to allow it to be shared in a library environment such as the directly embedded JDBC driver. Note that all synchronization is done at the class level, not the object level.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/db/FarragoDbSingleton.java#16 $

Author:

John V. Sichi

Field Summary

private static boolean	backupInProgress Flag indicating whether a database backup is already in progress
private static boolean	inShutdown Flag indicating whether FarragoDbSingleton is already in shutdown(), to help prevent recursive shutdown.
private static boolean	inShutdownConditional Flag indicating whether FarragoDbSingleton is already in shutdownConditional(int), to help prevent recursive shutdown.
protected static FarragoDatabase	instance Singleton instance, or null when nReferences == 0.
private static int	nReferences Reference count.
protected static Logger	tracer

Fields inherited from class org.eigenbase.util.CompoundClosableAllocation

allocations

Constructor Summary

FarragoDbSingleton()

Method Summary

(package private) static void	addSession(FarragoDatabase db, FarragoDbSession session)
private static int	countLoopbackSessions()
(package private) static void	disconnectSession(FarragoDbSession session)
static List<FarragoSession>	getSessions()
static List<FarragoSession>	getSessions(FarragoDatabase db) Retrieve a list of connected FarragoSession objects.
static boolean	isReferenced()
static FarragoDatabase	pinReference(FarragoSessionFactory sessionFactory) Establishes a database reference.
static FarragoDatabase	pinReference(FarragoSessionFactory sessionFactory, boolean requireExistingEngine) Establishes a database reference.
static boolean	setBackupFlag(boolean inProgress) Sets a flag indicating whether a backup is in progress.
static void	shutdown() Shuts down the database, killing any running sessions.
static boolean	shutdownConditional(int groundReferences) Conditionally shuts down the database depending on the number of references.

Methods inherited from class org.eigenbase.util.CompoundClosableAllocation

addAllocation, closeAllocation, forgetAllocation, hasAllocations

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eigenbase.util.ClosableAllocationOwner

addAllocation

Methods inherited from interface org.eigenbase.util.ClosableAllocation

closeAllocation

Methods inherited from interface org.eigenbase.util.ClosableAllocation

closeAllocation

Field Detail

tracer

protected static final Logger tracer

nReferences

private static int nReferences

Reference count.

instance

protected static FarragoDatabase instance

Singleton instance, or null when nReferences == 0.

inShutdown

private static boolean inShutdown

Flag indicating whether FarragoDbSingleton is already in shutdown(), to help prevent recursive shutdown.

backupInProgress

private static boolean backupInProgress

Flag indicating whether a database backup is already in progress

inShutdownConditional

private static boolean inShutdownConditional

Flag indicating whether FarragoDbSingleton is already in shutdownConditional(int), to help prevent recursive shutdown.

Constructor Detail

FarragoDbSingleton

public FarragoDbSingleton()

Method Detail

pinReference

public static FarragoDatabase pinReference(FarragoSessionFactory sessionFactory)

Establishes a database reference. If this is the first reference, the database will be loaded first; otherwise, the existing database is reused with an increased reference count.

Parameters:

sessionFactory - factory for various database-level objects

Returns:

loaded database

pinReference

public static FarragoDatabase pinReference(FarragoSessionFactory sessionFactory,
                                           boolean requireExistingEngine)

Establishes a database reference. If requireExistingEngine, a new database will not be loaded, even if this is the first reference.

Parameters:

sessionFactory - factory for various database-level objects

requireExistingEngine - true if require an already created reference

Returns:

loaded database

addSession

static void addSession(FarragoDatabase db,
                       FarragoDbSession session)

disconnectSession

static void disconnectSession(FarragoDbSession session)

getSessions

public static List<FarragoSession> getSessions(FarragoDatabase db)

Retrieve a list of connected FarragoSession objects. Each invocation produces a new List. Altering the list has no effect on the given FarragoDatabase.

The returned FarragoSession objects may be disconnected at any time. See FarragoSession.isClosed().

Parameters:

db - sessions are retrieved from this FarragoDatabase instance

Returns:

non-null List of FarragoSession objects

getSessions

public static List<FarragoSession> getSessions()

shutdownConditional

public static boolean shutdownConditional(int groundReferences)

Conditionally shuts down the database depending on the number of references.

Parameters:

groundReferences - threshold for shutdown; if actual number of sessions is greater than this, no shutdown takes place

Returns:

whether shutdown took place

shutdown

public static void shutdown()

Shuts down the database, killing any running sessions.

countLoopbackSessions

private static int countLoopbackSessions()

isReferenced

public static boolean isReferenced()

Returns:

true if the single currently exists

setBackupFlag

public static boolean setBackupFlag(boolean inProgress)

Sets a flag indicating whether a backup is in progress. If the flag is true and a backup is already in progress, then false is returned. Otherwise, true is returned.

Parameters:

inProgress - true if the flag is to be set, indicating that a backup is in progress

Returns:

true if setting of the flag was successful