Package org.springframework.data.mongodb.core.mapping

Annotation Interface DocumentReference

@Documented
@Retention(RUNTIME)
@Target(FIELD)
public @interface DocumentReference

A DocumentReference allows referencing entities in MongoDB using a flexible schema. While the goal is the same as when using DBRef, the store representation is different. The reference can be anything, a single value, an entire Document, basically everything that can be stored in MongoDB. By default, the mapping layer will use the referenced entities id value for storage and retrieval.

 public class Account {
   private String id;
   private Float total;
 }

 public class Person {
   private String id;
   @DocumentReference
   private List<Account> accounts;
 }

 Account account = ...

 mongoTemplate.insert(account);

 template.update(Person.class)
   .matching(where("id").is(...))
   .apply(new Update().push("accounts").value(account))
   .first();
 

lookup() allows defining a query filter that is independent from the _id field and in combination with writing converters offers a flexible way of defining references between entities.

 public class Book {
        private ObjectId id;
        private String title;

        @Field("publisher_ac") @DocumentReference(lookup = "{ 'acronym' : ?#{#target} }") private Publisher publisher;
 }

 public class Publisher {

        private ObjectId id;
        private String acronym;
        private String name;

        @DocumentReference(lazy = true) private List<Book> books;
 }

 @WritingConverter
 public class PublisherReferenceConverter implements Converter<Publisher, DocumentPointer<String>> {

        public DocumentPointer<String> convert(Publisher source) {
                return () -> source.getAcronym();
        }
 }
 

Since:

3.3

Author:

Christoph Strobl

See Also:

• MongoDB Reference Documentation

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
String	collection	The collection the referenced entity resides in.
String	db	The database the referenced entity resides in.
boolean	lazy	Controls whether the referenced entity should be loaded lazily.
String	lookup	The single document lookup query.
String	sort	A specific sort.

Element Details

db

String db

The database the referenced entity resides in. Uses the default database provided by MongoDatabaseFactory if empty.

See Also:

• MongoDatabaseFactory.getMongoDatabase()
• MongoDatabaseFactory.getMongoDatabase(String)

Default:

""

collection

String collection

The collection the referenced entity resides in. Defaults to the collection of the referenced entity type.

See Also:

• MongoPersistentEntity.getCollection()

Default:

""

lookup

String lookup

The single document lookup query. In case of an Collection or Map property the individual lookups are combined via an $or operator. target points to the source value (or document) stored at the reference property. Properties of target can be used to define the reference query.

Returns:

an _id based lookup.

Default:

"{ \'_id\' : ?#{#target} }"

sort

String sort

A specific sort.

Default:

""

lazy

boolean lazy

Controls whether the referenced entity should be loaded lazily. This defaults to false.

Returns:

false by default.

Default:

false