org.datanucleus.store.rdbms.valuegenerator

Class SequenceGenerator

java.lang.Object

org.datanucleus.store.valuegenerator.AbstractGenerator<T>

org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator<T>

org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator<Long>

org.datanucleus.store.rdbms.valuegenerator.SequenceGenerator

All Implemented Interfaces:

org.datanucleus.store.valuegenerator.ValueGenerator<Long>

public final class SequenceGenerator
extends AbstractRDBMSGenerator<Long>

This generator utilises datastore sequences. It uses a statement like

"select {sequence}.nextval from dual"

to get the next value in the sequence. It is datastore-dependent since there is no RDBMS-independent statement. SequenceGenerator works with Longs, so clients using this generator must cast the ID to Long.

Optional user properties

• sequence-catalog-name - catalog for the sequence
• sequence-schema-name - schema for the sequence
• key-initial-value - the initial value for the sequence
• key-cache-size - number of unique identifiers to cache
• key-min-value - determines the minimum value a sequence can generate
• key-max-value - determines the maximum value a sequence can generate
• key-database-cache-size - specifies how many sequence numbers are to be preallocated and stored in memory for faster access

Nested Class Summary

Nested classes/interfaces inherited from class org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator

org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator.ConnectionPreference

Field Summary

Fields

Modifier and Type	Field and Description
protected String	sequenceName Name of the sequence that we are creating values for

Fields inherited from class org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator

connection

Fields inherited from class org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator

connectionProvider, storeMgr

Fields inherited from class org.datanucleus.store.valuegenerator.AbstractGenerator

allocationSize, block, initialValue, name, properties, repositoryExists

Constructor Summary

Constructors

Constructor and Description
SequenceGenerator(String name, Properties props) Constructor.

Method Summary

Modifier and Type	Method and Description
protected boolean	createRepository() Method to create the sequence.
protected String	getSequenceName() Accessor for the sequence name to use (fully qualified with catalog/schema).
protected boolean	repositoryExists() Method to return if the repository already exists.
protected boolean	requiresRepository() Indicator for whether the generator requires its own repository.
protected org.datanucleus.store.valuegenerator.ValueGenerationBlock<Long>	reserveBlock(long size) Reserve a block of ids.

Methods inherited from class org.datanucleus.store.rdbms.valuegenerator.AbstractRDBMSGenerator

obtainGenerationBlock, requiresConnection

Methods inherited from class org.datanucleus.store.valuegenerator.AbstractDatastoreGenerator

getConnectionPreference, setConnectionProvider, setStoreManager

Methods inherited from class org.datanucleus.store.valuegenerator.AbstractGenerator

allocate, current, currentValue, getName, getStorageClass, next, nextValue, obtainGenerationBlock, reserveBlock

Methods inherited from class java.lang.Object

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

Field Detail

sequenceName

protected String sequenceName

Name of the sequence that we are creating values for

Constructor Detail

SequenceGenerator

public SequenceGenerator(String name,
                         Properties props)

Constructor.

Parameters:

name - Symbolic name for the generator

props - Properties controlling the behaviour of the generator

Method Detail

reserveBlock

protected org.datanucleus.store.valuegenerator.ValueGenerationBlock<Long> reserveBlock(long size)

Reserve a block of ids.

Specified by:

reserveBlock in class org.datanucleus.store.valuegenerator.AbstractGenerator<Long>

Parameters:

size - Block size

Returns:

The reserved block

getSequenceName

protected String getSequenceName()

Accessor for the sequence name to use (fully qualified with catalog/schema).

Returns:

The sequence name

requiresRepository

protected boolean requiresRepository()

Indicator for whether the generator requires its own repository. This class needs a repository so returns true.

Overrides:

requiresRepository in class org.datanucleus.store.valuegenerator.AbstractGenerator<Long>

Returns:

Whether a repository is required.

repositoryExists

protected boolean repositoryExists()

Method to return if the repository already exists.

Overrides:

repositoryExists in class org.datanucleus.store.valuegenerator.AbstractGenerator<Long>

Returns:

Whether the repository exists

createRepository

protected boolean createRepository()

Method to create the sequence.

Overrides:

createRepository in class org.datanucleus.store.valuegenerator.AbstractGenerator<Long>

Returns:

Whether it was created successfully.