spring-data-examples/mongodb/java8

Spring Data MongoDB - Java 8 examples

This project contains samples of Java 8 specific features of Spring Data (MongoDB).

Support for JDK 8's Stream for repository methods

Repository methods can use a Java 8 Stream as a return type which will cause the reading of the results and the to-object-conversion of the DBObject to happen while iterating over the stream.

public interface PersonRepository extends CrudRepository<Person, String> {

  @Override
  List<Person> findAll();

  //Custom Query method returning a Java 8 Stream
  @Query("{}")
  Stream<Person> findAllByCustomQueryWithStream();
}

The test cases in PersonRepositoryIntegrationTest oppose a plain List based query method with one that uses a Stream and shows how the former pulls all data into memory first and the iteration is done over the pre-populated list. The execution of the Stream-based method in contrast shows that the individual elements are read and converted while iterating the stream.