HIBERNATE TUTORIAL

HIBERNATE - Hibernate O/R Mapping

<generator> element

The optional <generator> child element names a Java class used to generate unique identifiers for instances of the persistent class. If any parameters are required to configure or initialize the generator instance, they are passed using the <param> element.

<id name="id" type="long" column="cat_id">
 

<generator class="org.hibernate.id.TableHiLoGenerator">

    <param name="table">uid_table</param>
<param name="column">next_hi_value_column</param>
  </generator>
</id>

All generators implement the interface org.hibernate.id.IdentifierGenerator. This is a very simple interface; some applications may choose to provide their own specialized implementations. However, Hibernate provides a range of built-in implementations. There are shortcut names for the built-in generators:

increment generates identifiers of type long, short or int that are unique only when no other process is inserting data into the same table. Do not use in a cluster. .
identity supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.
sequence uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a generator in Interbase. The returned identifier is of type long, short or int
hilo uses a hi/lo algorithm to efficiently generate identifiers of type long, short or int, given a table and column (by default hibernate_unique_key and next_hi respectively) as a source of hi values. The hi/lo algorithm generates identifiers that are unique only for a particular database.
seqhilo uses a hi/lo algorithm to efficiently generate identifiers of type long, short or int, given a named database sequence.
uuid uses a 128-bit UUID algorithm to generate identifiers of type string, unique within a network (the IP address is used). The UUID is encoded as a string of hexadecimal digits of length 32.
guid uses a database-generated GUID string on MS SQL Server and MySQL.
native picks identity, sequence or hilo depending upon the capabilities of the underlying database.
assigned lets the application to assign an identifier to the object before save() is called. This is the default strategy if no <generator> element is specified.
select retrieves a primary key assigned by a database trigger by selecting the row by some unique key and retrieving the primary key value
foreign uses the identifier of another associated object. Usually used in conjunction with a <one-to-one> primary key association.



Hibernate tutorial
Introduction to Hibernate
Overview of Hibernate
Features of Hibernate
Getting Started with Hibernate
Hibernate O/R Mapping

Mapping declaration

Mapping Document
<hibernate-mapping> element
<class> element
<id> element
<generator> element
<property> element
<many-to-one> element
<one-to-one> element
Hibernate Mapping In Depth
Hibernate Query Language
Hibernate Complete Example

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