The document provides an overview of Spring Data JPA, covering its basic features such as CRUD operations, query derivation, pagination, and specifications. It includes code examples demonstrating how to use Spring Data JPA to manage entities and perform database operations. Additional information on Spring Data JDBC is also mentioned as an alternative to Spring Data JPA.

1. © Copyright 2018 Pivotal Software, Inc. All rights Reserved.
May 2019
Spring Data JPA
0-100 in 60 minutes

3. “for they know not what they do”
(Lk 23:34)

4. Spring Data JPA builds on JPA
JPA Basics

5. JPA Basics
@Entity
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
@Version
Long version;
String firstName;
@OneToOne(cascade = CascadeType.ALL, orphanRemoval = true)
Address address;
@ManyToMany(cascade = CascadeType.ALL)
Set<Hobby> hobbies = new HashSet<>();
Gender gender;
}

6. JPA Basics
Person p = createPerson();
em.persist(p);
// select count(*) from Person
Person reloaded = em.find(Person.class, p.getId());
// select count(*) from Person
Person reloadedAgain = em
.createQuery("SELECT p FROM Person p " +
"WHERE p.id = :id", Person.class)
.setParameter("id", p.getId())
.getSingleResult();
// select count(*) from Person

7. JPA Basics
@Transactional
public class PersonService {
@Autowired
EntityManager em;
public void setName(Long id, String name) {
em.find(Person.class, id).setFirstName(name);
}
public Person loadPerson(Long id) {
return em.find(Person.class, id);
}
}

8. JPA Basics
Person person = personService.loadPerson(id);
person.getAddress();
person.getHobbies().forEach(System.out::println);

9. What does
Spring Data JPA do for you?
Spring Data JPA

10. CRUD
Spring Data JPA

11. CRUD
interface PersonRepository
extends JpaRepository<Person, Long> {}

12. CRUD
@Autowired
PersonRepository persons;
// …
Person p = persons.save(createPerson());
persons.findById(id);
persons.findAll();
persons.deleteAll();

13. Query Derivation
Spring Data JPA

14. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
List<Person> findByFirstName(String firstName);
boolean existsByAddress_CityContainsIgnoreCase(
String name);
}

15. Derived Queries
persons.findByFirstName("Jens");
persons.existsByAddress_CityContainsIgnoreCase(“aREST");

16. Annotated Queries
Spring Data JPA

17. Annotated Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
// …
@Query("SELECT CONCAT( p.firstName, 'n', a.zipCode, ' ', a.city) " +
"FROM Person p " +
"JOIN p.address AS a " +
"WHERE a.city LIKE :#{#city == null || #city.isEmpty() ?
'%' : #city}")
List<String> addressListByNullableCity(String city);
}

18. Pagination
Spring Data JPA

19. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
List<Person> findByFirstName(String firstName);
// …
}

20. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
Page<Person> findByFirstName(String firstName, Pageable page);
// …
}

21. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
Slice<Person> findByFirstName(String firstName, Pageable page);
// …
}

22. Projections
Spring Data JPA

23. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
List<Person> findByFirstName(String firstName);
// …
}

24. Derived Queries
interface PersonRepository
extends JpaRepository<Person, Long> {
List<SimplePerson> findSimplyByFirstName(String firstName);
// …
}

25. Derived Queries
public interface SimplePerson {
String getFirstName();
Gender getGender();
@Value("#{target.address.city + ' in ' + target.address.state}")
String getAddress();
}

26. Conversions
Spring Data JPA

27. Query By Example
Spring Data JPA

28. Query by Example
Person pattern = new Person(
null,
new Address(null, null, "germany"),
Gender.MALE,
null
);
Example<Person> strict = Example.of(pattern);
persons.findAll(strict);

29. Query by Example
Example<Person> lenient = Example.of(
pattern,
ExampleMatcher.matchingAll().withIgnoreCase()
);
persons.findAll(lenient);

30. Specifications
Spring Data JPA

31. Specifications
interface PersonRepository
extends JpaRepository<Person, Long>, JpaSpecificationExecutor<Person>
{
// …
}

32. Specifications
persons.findAll(notFrom("new"))
// …
Specification<Person> notFrom(String cityPart) {
return (Specification<Person>)
(Root<Person> root, CriteriaQuery<?> cq, CriteriaBuilder cb) ->
cb.not(
cb.like(
root.get("address").get("city"),
"%" + cityPart + "%"
)
);
}

33. Querydsl Support
Spring Data JPA

34. Specifications
interface PersonRepository
extends JpaRepository<Person, Long>, QueryDslPredicateExecutor
{
// …
}

35. Specifications
persons.findAll(notFrom("new"))
// …
BooleanExpression notFrom(String cityPart) {
return QPerson.person
.address.city
.containsIgnoreCase(cityPart).not();
}

36. What is Spring Data JDBC?
Alternativ to Spring Data JPA

37. What if something breaks?
Spring Data JPA or JPA

38. References
! Github: https://github.com/spring-projects/spring-data-jpa
! Reference: https://docs.spring.io/spring-data/data-jpa/docs/current/reference/html/
! Official examples: https://github.com/spring-projects/spring-data-examples/tree/
master/jpa
! Examples for these slides: https://github.com/schauder/talk-spring-data-jpa-0-100/
tree/master/example
! Article about specifications and Querydsl with Spring Data JPA: https://spring.io/blog/
2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/

39. Jens Schauder
! Spring Data JPA
! Spring Data JDBC
! jschauder@pivotal.io
! Father
! Plays (Roleplaying) Games
! Fitness & Sports
! @jensschauder
! blog.schauderhaft.de

40. Attribution
! https://upload.wikimedia.org/wikipedia/commons/8/8d/
Shimano_three_gear_hub_lever.jpg (CC-BY-SA 3.0)