From da2542a01cb35d08611aa69b7bf1f0bcf44bae0b Mon Sep 17 00:00:00 2001 From: Gavin Date: Wed, 10 May 2023 20:28:46 +0200 Subject: [PATCH] mapping tables and columns --- .../main/asciidoc/introduction/Mapping.adoc | 48 +++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/documentation/src/main/asciidoc/introduction/Mapping.adoc b/documentation/src/main/asciidoc/introduction/Mapping.adoc index 12e428b684..ccecdde04c 100644 --- a/documentation/src/main/asciidoc/introduction/Mapping.adoc +++ b/documentation/src/main/asciidoc/introduction/Mapping.adoc @@ -150,3 +150,51 @@ is a bad idea, since it's impossible to create a foreign key constraint that tar // Hibernate doesn't support mixing ``InheritanceType``s within a single entity hierarchy. // However, it's possible to emulate a mix of `SINGLE_TABLE` and `JOINED` inheritance using the `@SecondaryTable` annotation. +[[table-mappings]] +=== Mapping to tables + +The following annotations specify exactly how elements of the domain model map to tables of the relational model: + +|=== +| Annotation | Purpose + +| `@Table` | Map an entity class to its primary table +| `@SecondaryTable` | Define a secondary table for an entity class +| `@JoinTable` | Map a many-to-many association to its association table +| `@CollectionTable` | Map an `@ElementCollection` to its table +|=== + +By default, an entity maps to a single table, which may be specified using `@Table`: + +[source,java] +---- +@Entity +@Table(name="People") +class Person { ... } +---- + +However, the `@SecondaryTable` annotation allows us to spread its attributes across multiple _secondary tables_. + +[source,java] +---- +@Entity +@Table(name="Books") +@SecondaryTable(name="Editions") +class Book { ... } +---- + +[[column-mappings]] +=== Mapping to columns + +These annotations specify how elements of the domain model map to columns of tables in the relational model: + +|=== +| Annotation | Purpose + +| `@Column` | Map an attribute to a column +| `@JoinColumn` | Map an association to a foreign key column +| `@PrimaryKeyJoinColumn` | Map the primary key used to join a secondary table with its primary, or a subclass table in `JOINED` inheritance with its root class table +| `@OrderColumn` | Specifies a column that should be used to maintain the order of a `List`. +| `@MapKeyColumn` | Specified a column that should be used to persist the keys of a `Map`. +|=== +