8. Map
Definition: A map is a simple name-value pair list stored on a first rank collection.
Scenario: First rank class Foo has a map containing people's ages indexed by their names
Hibernate Mapping:
In Hibernate, this could be mapped as follows:
Table Schema:
A simple extra table, Ages, is used to store the name and age string-value pair. Note that the map needs its own identity column too: id.
Bidirectionality:
Bidirectionality has no meaning for a map.
Definition: A map is a simple name-value pair list stored on a first rank collection.
Scenario: First rank class Foo has a map containing people's ages indexed by their names
|
Map Foo.getAges() // returns a collection of String name-value pairs |
Hibernate Mapping:
In Hibernate, this could be mapped as follows:
|
<class name="Foo" table="foo"> ... <map role="ages"> <key column="id"/> <index column="name" type="string"/> <element column="age" type="string"/> </map> </class> |
Table Schema:
|
Foo |
|
id |
|
Ages |
||
|
id |
name |
age |
A simple extra table, Ages, is used to store the name and age string-value pair. Note that the map needs its own identity column too: id.
Bidirectionality:
Bidirectionality has no meaning for a map.