org.hibernate.id.enhanced
Class TableGenerator

java.lang.Object
  extended by 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)


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