Hibernate
/
hibernate-orm
mirror of https://github.com/hibernate/hibernate-orm
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

improve code examples for generated ids in Intro

This commit is contained in:
Gavin 2023-05-29 11:32:00 +02:00 committed by Gavin King
parent 81d0bbccc6
commit 2728cbe014
1 changed files with 17 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
documentation/src/main/asciidoc/introduction/Entities.adoc
View File

@ -239,12 +239,18 @@ JPA defines the following strategies for generating ids, which are enumerated by
| `GenerationType.AUTO` | `Long` or `Integer` | Selects `SEQUENCE`, `TABLE`, or `UUID` based on the identifier type and capabilities of the database
|===
For example, the following id maps to a SQL `identity`, `auto_increment`, or `bigserial` column:
For example, this UUID is generated in Java code:
[source,java]
----
@Id @GeneratedValue(strategy=IDENTITY)
Long id;
@Id @GeneratedValue UUID id; // AUTO strategy selects UUID based on the field type
----
This id maps to a SQL `identity`, `auto_increment`, or `bigserial` column:
[source,java]
----
@Id @GeneratedValue(strategy=IDENTITY) Long id;
----
The `@SequenceGenerator` and `@TableGenerator` annotations allow further control over `SEQUENCE` and `TABLE` generation respectively.
@ -253,8 +259,7 @@ Consider this sequence generator:
[source,java]
----
@SequenceGenerator(name="bookSeq", sequenceName="seq_book",
initialValue = 5, allocationSize=10)
@SequenceGenerator(name="bookSeq", sequenceName="seq_book", initialValue = 5, allocationSize=10)
----
Values are generated using a database sequence defined as follows:
@ -279,7 +284,8 @@ Any identifier attribute may now make use of the generator named `bookSeq`:
[source,java]
----
@Id @GeneratedValue(strategy=SEQUENCE, generator="bookSeq")
@Id
@GeneratedValue(strategy=SEQUENCE, generator="bookSeq") // reference to generator defined elsewhere
Long id;
----
@ -287,9 +293,9 @@ Actually, it's extremely common to place the `@SequenceGenerator` annotation on
[source,java]
----
@Id @GeneratedValue(strategy=SEQUENCE, generator="bookSeq")
@SequenceGenerator(name="bookSeq", sequenceName="seq_book",
initialValue = 5, allocationSize=10)
@Id
@GeneratedValue(strategy=SEQUENCE, generator="bookSeq") // reference to generator defined below
@SequenceGenerator(name="bookSeq", sequenceName="seq_book", initialValue = 5, allocationSize=10)
Long id;
----
@ -753,7 +759,7 @@ We may explicitly specify a Java type using the `@JavaType` annotation, but for
[source,java]
----
@JavaType(LongJavaType.class) // not needed, this is the default JavaType for long
@JavaType(LongJavaType.class) // not needed, this is the default JavaType for long
long currentTimeMillis;
----
@ -936,6 +942,7 @@ In this example data model, we can see the sorts of associations which are possi
image::images/associations.png[Example data model,align="center",pdfwidth=90%]
[%unbreakable]
[TIP]
// .One-to-one associations and subtyping
====