org.datanucleus.store.rdbms.valuegenerator

Class SequenceGenerator

java.lang.Object

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

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

org.datanucleus.store.rdbms.valuegenerator.SequenceGenerator

All Implemented Interfaces:

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

public final class SequenceGenerator
extends org.datanucleus.store.valuegenerator.AbstractConnectedGenerator<Long>

ValueGenerator utilising datastore (RDBMS) 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

TODO Change structure to not override obtainGenerationBlock so we can follow the superclass process and commonise more code.

Nested Class Summary

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

org.datanucleus.store.valuegenerator.AbstractConnectedGenerator.ConnectionPreference

Field Summary

Fields

Modifier and Type	Field and Description
protected org.datanucleus.store.connection.ManagedConnection	connection Connection to the datastore.
protected boolean	repositoryExists Flag for whether we know that the repository exists.
protected String	sequenceName Name of the sequence that we are creating values for

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

connectionProvider, properties

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

allocationSize, block, initialValue, name, storeMgr

Fields inherited from interface org.datanucleus.store.valuegenerator.ValueGenerator

PROPERTY_CATALOG_NAME, PROPERTY_CLASS_NAME, PROPERTY_COLUMN_NAME, PROPERTY_FIELD_NAME, PROPERTY_KEY_CACHE_SIZE, PROPERTY_KEY_DATABASE_CACHE_SIZE, PROPERTY_KEY_INITIAL_VALUE, PROPERTY_KEY_MAX_VALUE, PROPERTY_KEY_MIN_VALUE, PROPERTY_ROOT_CLASS_NAME, PROPERTY_SCHEMA_NAME, PROPERTY_SEQUENCE_NAME, PROPERTY_SEQUENCETABLE_CATALOG, PROPERTY_SEQUENCETABLE_NAME_COLUMN, PROPERTY_SEQUENCETABLE_NEXTVAL_COLUMN, PROPERTY_SEQUENCETABLE_SCHEMA, PROPERTY_SEQUENCETABLE_TABLE, PROPERTY_TABLE_NAME

Constructor Summary

Constructors

Constructor and Description
SequenceGenerator(org.datanucleus.store.StoreManager storeMgr, String name, Properties props) Constructor.

Method Summary

Modifier and Type	Method and Description
protected boolean	createRepository() Method to create the sequence.
static Class	getStorageClass() Accessor for the storage class for values generated with this generator.
protected org.datanucleus.store.valuegenerator.ValueGenerationBlock<Long>	obtainGenerationBlock(int number) Get a new ValueGenerationBlock with the specified number of ids.
protected boolean	repositoryExists() Method to return if the repository already exists.
protected org.datanucleus.store.valuegenerator.ValueGenerationBlock<Long>	reserveBlock(long size) Reserve a block of ids.

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

getConnectionPreference, setConnectionProvider

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

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

Methods inherited from class java.lang.Object

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

Field Detail

connection

protected org.datanucleus.store.connection.ManagedConnection connection

Connection to the datastore.

repositoryExists

protected boolean repositoryExists

Flag for whether we know that the repository exists.

sequenceName

protected String sequenceName

Name of the sequence that we are creating values for

Constructor Detail

SequenceGenerator

public SequenceGenerator(org.datanucleus.store.StoreManager storeMgr,
                         String name,
                         Properties props)

Constructor.

Parameters:

storeMgr - StoreManager

name - Symbolic name for the generator

props - Properties controlling the behaviour of the generator

Method Detail

getStorageClass

public static Class getStorageClass()

Accessor for the storage class for values generated with this generator.

Returns:

Storage class (in this case Long.class)

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

repositoryExists

protected boolean repositoryExists()

Method to return if the repository already exists.

Returns:

Whether the repository exists

createRepository

protected boolean createRepository()

Method to create the sequence.

Returns:

Whether it was created successfully.

obtainGenerationBlock

protected org.datanucleus.store.valuegenerator.ValueGenerationBlock<Long> obtainGenerationBlock(int number)

Get a new ValueGenerationBlock with the specified number of ids.

Overrides:

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

Parameters:

number - The number of additional ids required

Returns:

the ValueGenerationBlock