org.apache.slide.store
Interface SequenceStore

All Superinterfaces:

Service, javax.transaction.xa.XAResource

All Known Subinterfaces:

Store

All Known Implementing Classes:

AbstractStore

public interface SequenceStore

extends Service

Store for sequence support. A sequence is an entity that provides unique numbers. A store supports sequences when it implements this interface and the method isSupported returns true.

Version:

$Revision: 1.3 $

Field Summary

Fields inherited from interface javax.transaction.xa.XAResource

TMENDRSCAN, TMFAIL, TMJOIN, TMNOFLAGS, TMONEPHASE, TMRESUME, TMSTARTRSCAN, TMSUCCESS, TMSUSPEND, XA_OK, XA_RDONLY

Method Summary

boolean	createSequence(java.lang.String sequenceName) Creates a sequence if it does not already exist.
boolean	isSequenceSupported() Checks if this store instance actually supports sequences.
long	nextSequenceValue(java.lang.String sequenceName) Gets the next value of the sequence.
boolean	sequenceExists(java.lang.String sequenceName) Checks if the sequence already exists.

Methods inherited from interface org.apache.slide.common.Service

cacheResults, connect, connect, connectIfNeeded, connectIfNeeded, disconnect, getLogger, initialize, isConnected, reset, setNamespace, setParameters, setScope

Methods inherited from interface javax.transaction.xa.XAResource

commit, end, forget, getTransactionTimeout, isSameRM, prepare, recover, rollback, setTransactionTimeout, start

Method Detail

isSequenceSupported

public boolean isSequenceSupported()

Checks if this store instance actually supports sequences. It may seem clear this store supports sequences as it implements this interface, but a request to the underlying persistence store might be needed to dynamically find out.

Returns:

true if the store supports sequences, false otherwise

sequenceExists

public boolean sequenceExists(java.lang.String sequenceName)
                       throws ServiceAccessException

Checks if the sequence already exists.

Parameters:

sequenceName - the name of the sequence you want to check

Returns:

true if the sequence already exists, false otherwise

Throws:

ServiceAccessException - if anything goes wrong while accessing the sequence

createSequence

public boolean createSequence(java.lang.String sequenceName)
                       throws ServiceAccessException

Creates a sequence if it does not already exist.

Parameters:

sequenceName - the name of the sequence you want to create

Returns:

true if the sequence has been created, false if it already existed

Throws:

ServiceAccessException - if anything goes wrong while accessing the sequence

nextSequenceValue

public long nextSequenceValue(java.lang.String sequenceName)
                       throws ServiceAccessException

Gets the next value of the sequence. Note that the sequence may not deliver consecutive or continuous values. The only thing that is assured is the value will be unique in the scope of the sequence, i.e. this method will never return the same value for the same sequence. A sequence of valid values might be

1,2,3,4,5,...

, but it might just as well be

10,787875845,1,2,434,...

. However, it may not be

1,2,1,3,...

. as a sequence must never return the same value twice or more times.

Returns:

the next value of the sequence

Throws:

ServiceAccessException - if anything goes wrong while accessing the sequence