Add annotation-based Collation support [DATAMONGO-1854]

[spring-projects-issues]

Shiv Veeram opened DATAMONGO-1854 and commented

Provide collation support in mongo repository interface

---

Reference URL: https://jira.mongodb.org/browse/SERVER-1920

Issue Links:

• DATAMONGO-2284 Annotation Support for Collations
  ("is duplicated by")
• DATAMONGO-1518 Add support for Collations

Referenced from: pull request #644

2 votes, 2 watchers

[spring-projects-issues]

Christoph Strobl commented

Collation support for Reactive/MongoRepository interfaces could look like this:

1. Via @Query Annotaion

The @Query annotation should be extended to have a collation attribute. The attribute can be a fixed String holding the collation value, the collation JSON representation, a parameter binding flag, of even a JSON allowing parameter binding. Also SpEL might be an option.

@Query(collation = "en_US")
List<Entry> findAllByFixedCollation();

@Query(collation = "{ 'locale' :  'en_US' }")
List<Entry> findAllByFixedJsonCollation();

@Query(collation = "?0")
List<Entry> findAllByDynamicCollation(String collation);

@Query(collation = "{ 'locale' :  ?0 }")
List<Entry> findAllByDynamicJsonCollation(String collation);

@Query(collation = "?#{[0]}")
List<Entry> findAllByDynamicSpElCollation(String collation);

2. Via typed Parameter

...Collation parameter is auto detected via its type (o.s.d.m.core.query.Collation) and applied to the Query.

List<Entry> findAllBy(Collation collation)

A comination of 1) & 2) should lead to an error

[spring-projects-issues]

Christoph Strobl commented

Intoducing a new @Collation annotation would allow us to add a CollationResolver that could react on

Collation on domain type

@Document
@Collation("en_US")
public class DomainType {
	
}

1. Apply the collation value when creating a MongoDB collection via MongoTemplate#createCollection(java.lang.Class)
2. Apply the collation to indices created for the domain type
3. Apply the collation to queries issued against the collection
   1. If the Query does not explicitly specify an Collation.
   2. To use the Server default, Query would have to have Collation#SIMPLE set.

Collation on repository

@Collation("en_US")
public interface MyRepo extends Repository<...> {
	
}

1. Apply the collation to queries issued against the collection
2. Apply the collation to indexes auto created for finder methods.

Collation on repository finder method

@Collation("en_US")
public interface MyRepo extends Repository<...> {
	
    @Collation("de_AT")
    List<Entry> findAllByFixedCollation();

    @Collation("?0")
    List<Entry> findAllByDynamicCollation(String collation);
}

1. Override the potential default collation for specific finders.
2. Apply the collation to indexes auto created for finder methods.