Significance of the generator attribute in hibernate

 

1. Identity: used for MySQL databases. Features: Incremental

<ID name = "ID" column = "ID">

<Generator class = "Identity"/>

</ID>

Note: When using an incremental sequence for a MySQL database, you must specify the primary key as the auto_increment attribute when creating a table.

2. sequence: used for Oracle databases

<ID name = "ID" column = "ID">

<Generator class = "sequence">

<Param name = "sequence"> sequence name </param>

</Generator>

</ID>

3. Native: used across databases, produced by underlying dialects.

Default. sequence is hibernate_sequence

<ID name = "ID" column = "ID">

<Generator class = "native"/>

</ID>

Note: When native is used, Hibernate searches for the hibernate_sequence sequence in Oracle by default.

If the sequence does not exist in Oracle, an error is returned when you connect to the Oracle database.

4. HiLo: Create the hi_value table and create the next_value column by merging the IDs of the high and low bits. An initial value is required.

<ID name = "ID" column = "ID">

<Generator class = "HiLo">

<Param name = "table"> high_val </param>

<Param name = "column"> nextval </param>

<Param name = "max_lo"> 5 </param>

</Generator>

</ID>

5. sequencehilo: The same as the high and low merging ID. Create a sequence without table creation.

<ID name = "ID" column = "ID">

<Generator class = "HiLo">

<Param name = "sequence"> high_val_seq </param>

<Param name = "max_lo"> 5 </param>

</Generator>

</ID>

6. assigned: User-Defined ID;

<ID name = "ID" column = "ID">

<Generator class = "assigned"/>

</ID>

7. Foreign: used for one-to-one relationship to share the master key, the two IDs are the same.