Package org.hibernate.id.enhanced

Class TableGenerator

java.lang.Object
org.hibernate.engine.TransactionHelper
org.hibernate.id.enhanced.TableGenerator
All Implemented Interfaces:
Configurable, IdentifierGenerator, PersistentIdentifierGenerator
public class TableGenerator extends TransactionHelper 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 Details

  • Constructor Details

    • TableGenerator

      public TableGenerator()

  • Method Details

    • generatorKey

      public Object generatorKey()
      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
      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
      Parameters:
      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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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)
      Generate a new identifier.
      Specified by:
      generate in interface IdentifierGenerator
      Parameters:
      session -
      obj - the entity or toplevel collection for which the id is being generated
      Returns:
      a new identifier

    • doWorkInCurrentTransaction

      public Serializable doWorkInCurrentTransaction(Connection conn, String sql) throws SQLException
      The work to be done
      Specified by:
      doWorkInCurrentTransaction in class TransactionHelper
      Throws:
      SQLException

    • sqlCreateStrings

      public String[] sqlCreateStrings(Dialect dialect) throws HibernateException
      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
      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)