org.hibernate.id.enhanced
Class TableGenerator

java.lang.Object
  org.hibernate.id.enhanced.TableGenerator

All Implemented Interfaces:

Configurable, IdentifierGenerator, PersistentIdentifierGenerator

public class TableGenerator
extends Object
implements PersistentIdentifierGenerator, Configurable

An enhanced version of table-based id generation.

Unlike the simplistic legacy one (which, btw, was only ever intended for subclassing support) we "segment" the table into multiple values. Thus a single table can actually serve as the persistent storage for multiple independent generators. One approach would be to segment the values by the name of the entity for which we are performing generation, which would mean that we would have a row in the generator table for each entity name. Or any configuration really; the setup is very flexible.

In this respect it is very similar to the legacy MultipleHiLoPerTableGenerator in terms of the underlying storage structure (namely a single table capable of holding multiple generator values). The differentiator is, as with SequenceStyleGenerator as well, the externalized notion of an optimizer.

NOTE that by default we use a single row for all generators (based on DEF_SEGMENT_VALUE). The configuration parameter CONFIG_PREFER_SEGMENT_PER_ENTITY can be used to change that to instead default to using a row for each entity name.

Configuration parameters:

NAME	DEFAULT	DESCRIPTION
TABLE_PARAM	DEF_TABLE	The name of the table to use to store/retrieve values
VALUE_COLUMN_PARAM	DEF_VALUE_COLUMN	The name of column which holds the sequence value for the given segment
SEGMENT_COLUMN_PARAM	DEF_SEGMENT_COLUMN	The name of the column which holds the segment key
SEGMENT_VALUE_PARAM	DEF_SEGMENT_VALUE	The value indicating which segment is used by this generator; refers to values in the SEGMENT_COLUMN_PARAM column
SEGMENT_LENGTH_PARAM	DEF_SEGMENT_LENGTH	The data length of the SEGMENT_COLUMN_PARAM column; used for schema creation
INITIAL_PARAM	DEFAULT_INITIAL_VALUE	The initial value to be stored for the given segment
INCREMENT_PARAM	DEFAULT_INCREMENT_SIZE	The increment size for the underlying segment; see the discussion on Optimizer for more details.
OPT_PARAM	depends on defined increment size	Allows explicit definition of which optimization strategy to use

Field Summary

static String	CONFIG_PREFER_SEGMENT_PER_ENTITY
static String	DEF_SEGMENT_COLUMN
static int	DEF_SEGMENT_LENGTH
static String	DEF_SEGMENT_VALUE
static String	DEF_TABLE
static String	DEF_VALUE_COLUMN
static int	DEFAULT_INCREMENT_SIZE
static int	DEFAULT_INITIAL_VALUE
static String	INCREMENT_PARAM
static String	INITIAL_PARAM
static String	OPT_PARAM
static String	SEGMENT_COLUMN_PARAM
static String	SEGMENT_LENGTH_PARAM
static String	SEGMENT_VALUE_PARAM
static String	TABLE_PARAM
static String	VALUE_COLUMN_PARAM

Fields inherited from interface org.hibernate.id.PersistentIdentifierGenerator

CATALOG, IDENTIFIER_NORMALIZER, PK, SCHEMA, TABLE, TABLES

Fields inherited from interface org.hibernate.id.IdentifierGenerator

ENTITY_NAME, JPA_ENTITY_NAME

Constructor Summary

TableGenerator()

Method Summary

protected String	buildInsertQuery()
protected String	buildSelectQuery(Dialect dialect)
protected String	buildUpdateQuery()
void	configure(Type type, Properties params, Dialect dialect) Configure this instance, given the value of parameters specified by the user as <param> elements.
protected String	determineDefaultSegmentValue(Properties params) Used in the cases where determineSegmentValue(java.util.Properties) is unable to determine the value to use.
protected String	determineGeneratorTableName(Properties params, Dialect dialect) Determine the table name to use for the generator values.
protected int	determineIncrementSize(Properties params)
protected int	determineInitialValue(Properties params)
protected String	determineSegmentColumnName(Properties params, Dialect dialect) Determine the name of the column used to indicate the segment for each row.
protected int	determineSegmentColumnSize(Properties params) Determine the size of the segment column Called during configuration.
protected String	determineSegmentValue(Properties params) Determine the segment value corresponding to this generator instance.
protected String	determineValueColumnName(Properties params, Dialect dialect) Determine the name of the column in which we will store the generator persistent value.
Serializable	generate(SessionImplementor session, Object obj) Generate a new identifier.
Object	generatorKey() Return a key unique to the underlying database objects.
Type	getIdentifierType() Type mapping for the identifier.
int	getIncrementSize() The amount of increment to use.
int	getInitialValue() The initial value to use when we find no previous state in the generator table corresponding to our sequence.
Optimizer	getOptimizer() The optimizer being used by this generator.
String	getSegmentColumnName() The name of the column in which we store the segment to which each row belongs.
String	getSegmentValue() The value in segment column which corresponding to this generator instance.
int	getSegmentValueLength() The size of the segment column in the underlying table.
long	getTableAccessCount() Getter for property 'tableAccessCount'.
String	getTableName() The name of the table in which we store this generator's persistent state.
String	getValueColumnName() The name of the column in which we store our persistent generator value.
String[]	sqlCreateStrings(Dialect dialect) The SQL required to create the underlying database objects.
String[]	sqlDropStrings(Dialect dialect) The SQL required to remove the underlying database objects.

Methods inherited from class java.lang.Object

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

Field Detail

CONFIG_PREFER_SEGMENT_PER_ENTITY

public static final String CONFIG_PREFER_SEGMENT_PER_ENTITY

See Also:

Constant Field Values

TABLE_PARAM

public static final String TABLE_PARAM

See Also:

Constant Field Values

DEF_TABLE

public static final String DEF_TABLE

See Also:

Constant Field Values

VALUE_COLUMN_PARAM

public static final String VALUE_COLUMN_PARAM

See Also:

Constant Field Values

DEF_VALUE_COLUMN

public static final String DEF_VALUE_COLUMN

See Also:

Constant Field Values

SEGMENT_COLUMN_PARAM

public static final String SEGMENT_COLUMN_PARAM

See Also:

Constant Field Values

DEF_SEGMENT_COLUMN

public static final String DEF_SEGMENT_COLUMN

See Also:

Constant Field Values

SEGMENT_VALUE_PARAM

public static final String SEGMENT_VALUE_PARAM

See Also:

Constant Field Values

DEF_SEGMENT_VALUE

public static final String DEF_SEGMENT_VALUE

See Also:

Constant Field Values

SEGMENT_LENGTH_PARAM

public static final String SEGMENT_LENGTH_PARAM

See Also:

Constant Field Values

DEF_SEGMENT_LENGTH

public static final int DEF_SEGMENT_LENGTH

See Also:

Constant Field Values

INITIAL_PARAM

public static final String INITIAL_PARAM

See Also:

Constant Field Values

DEFAULT_INITIAL_VALUE

public static final int DEFAULT_INITIAL_VALUE

See Also:

Constant Field Values

INCREMENT_PARAM

public static final String INCREMENT_PARAM

See Also:

Constant Field Values

DEFAULT_INCREMENT_SIZE

public static final int DEFAULT_INCREMENT_SIZE

See Also:

Constant Field Values

OPT_PARAM

public static final String OPT_PARAM

See Also:

Constant Field Values

Constructor Detail

TableGenerator

public TableGenerator()

Method Detail

generatorKey

public Object generatorKey()

Description copied from interface: PersistentIdentifierGenerator

Return a key unique to the underlying database objects. Prevents us from trying to create/remove them multiple times.

Specified by:

generatorKey in interface PersistentIdentifierGenerator

Returns:

Object an identifying key for this generator

getIdentifierType

public final Type getIdentifierType()

Type mapping for the identifier.

Returns:

The identifier type mapping.

getTableName

public final String getTableName()

The name of the table in which we store this generator's persistent state.

Returns:

The table name.

getSegmentColumnName

public final String getSegmentColumnName()

The name of the column in which we store the segment to which each row belongs. The value here acts as PK.

Returns:

The segment column name

getSegmentValue

public final String getSegmentValue()

The value in segment column which corresponding to this generator instance. In other words this value indicates the row in which this generator instance will store values.

Returns:

The segment value for this generator instance.

getSegmentValueLength

public final int getSegmentValueLength()

The size of the segment column in the underlying table.

NOTE : should really have been called 'segmentColumnLength' or even better 'segmentColumnSize'

Returns:

the column size.

getValueColumnName

public final String getValueColumnName()

The name of the column in which we store our persistent generator value.

Returns:

The name of the value column.

getInitialValue

public final int getInitialValue()

The initial value to use when we find no previous state in the generator table corresponding to our sequence.

Returns:

The initial value to use.

getIncrementSize

public final int getIncrementSize()

The amount of increment to use. The exact implications of this depends on the optimizer being used.

Returns:

The increment amount.

getOptimizer

public final Optimizer getOptimizer()

The optimizer being used by this generator.

Returns:

Out optimizer.

getTableAccessCount

public final long getTableAccessCount()

Getter for property 'tableAccessCount'. Only really useful for unit test assertions.

Returns:

Value for property 'tableAccessCount'.

configure

public void configure(Type type,
                      Properties params,
                      Dialect dialect)
               throws MappingException

Description copied from interface: Configurable

Configure this instance, given the value of parameters specified by the user as <param> elements. This method is called just once, following instantiation.

Specified by:

configure in interface Configurable

params - param values, keyed by parameter name

Throws:

MappingException

determineGeneratorTableName

protected String determineGeneratorTableName(Properties params,
                                             Dialect dialect)

Determine the table name to use for the generator values.

Called during configuration.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

dialect - The dialect in effect

Returns:

The table name to use.

See Also:

getTableName()

determineSegmentColumnName

protected String determineSegmentColumnName(Properties params,
                                            Dialect dialect)

Determine the name of the column used to indicate the segment for each row. This column acts as the primary key.

Called during configuration.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

dialect - The dialect in effect

Returns:

The name of the segment column

See Also:

getSegmentColumnName()

determineValueColumnName

protected String determineValueColumnName(Properties params,
                                          Dialect dialect)

Determine the name of the column in which we will store the generator persistent value.

Called during configuration.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

dialect - The dialect in effect

Returns:

The name of the value column

See Also:

getValueColumnName()

determineSegmentValue

protected String determineSegmentValue(Properties params)

Determine the segment value corresponding to this generator instance.

Called during configuration.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

Returns:

The name of the value column

See Also:

getSegmentValue()

determineDefaultSegmentValue

protected String determineDefaultSegmentValue(Properties params)

Used in the cases where determineSegmentValue(java.util.Properties) is unable to determine the value to use.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

Returns:

The default segment value to use.

determineSegmentColumnSize

protected int determineSegmentColumnSize(Properties params)

Determine the size of the segment column

Called during configuration.

Parameters:

params - The params supplied in the generator config (plus some standard useful extras).

Returns:

The size of the segment column

See Also:

getSegmentValueLength()

determineInitialValue

protected int determineInitialValue(Properties params)

determineIncrementSize

protected int determineIncrementSize(Properties params)

buildSelectQuery

protected String buildSelectQuery(Dialect dialect)

buildUpdateQuery

protected String buildUpdateQuery()

buildInsertQuery

protected String buildInsertQuery()

generate

public Serializable generate(SessionImplementor session,
                             Object obj)

Description copied from interface: IdentifierGenerator

Generate a new identifier.

Specified by:

generate in interface IdentifierGenerator

obj - the entity or toplevel collection for which the id is being generated

Returns:

a new identifier

sqlCreateStrings

public String[] sqlCreateStrings(Dialect dialect)
                          throws HibernateException

Description copied from interface: PersistentIdentifierGenerator

The SQL required to create the underlying database objects.

Specified by:

sqlCreateStrings in interface PersistentIdentifierGenerator

Parameters:

dialect - The dialect against which to generate the create command(s)

Returns:

The create command(s)

Throws:

HibernateException - problem creating the create command(s)

sqlDropStrings

public String[] sqlDropStrings(Dialect dialect)
                        throws HibernateException

Description copied from interface: PersistentIdentifierGenerator

The SQL required to remove the underlying database objects.

Specified by:

sqlDropStrings in interface PersistentIdentifierGenerator

Parameters:

dialect - The dialect against which to generate the drop command(s)

Returns:

The drop command(s)

Throws:

HibernateException - problem creating the drop command(s)