JPA - Beyond Copy-Paste

Transcript

1. @jkubrynski / kubrynski.com JPA - BEYOND COPY-PASTE JAKUB KUBRYNSKI jk@devskiller.com / @jkubrynski / http://kubrynski.com
2. WHOAMI DEVSKILLER CO-FOUNDER BOTTEGA TRAINER DEVOXX.PL PROGRAM COMMITTEE SPRING CLOUD CONTRACT CO-AUTHOR
4. ALL NON-TRIVIAL ABSTRACTIONS, TO SOME DEGREE, ARE LEAKY. JOEL SPOLSKY
5. @Entity public class Product { @Id @GeneratedValue private Long id; @Column private String name; // ... }
6. @Entity public class Product { @Id @GeneratedValue private Long id; @Column // it does exactly nothing private String name; // ... }
7. @Transactional @Service public class ProductService { public void updatePrice(Long productId, Money newPrice) { Product product = productRepository.find(productId); product.setPrice(newPrice); productRepository.save(product); } }
8. @Transactional @Service public class ProductService { public void updatePrice(Long productId, Money newPrice) { Product product = productRepository.find(productId); product.setPrice(newPrice); productRepository.save(product); // it does exactly nothing } }
9. FIELDS VS GETTERS @Entity public class Product { private Long id; private String name; @Id public Long getId() { return id; } }
10. MIXED ACCESS @Entity @Access(AccessType.FIELD) public class Product { private Long id; private String name; @Id @Access(AccessType.PROPERTY) public Long getId() { return id; } }
11. @Entity public class Order { }
12. @Entity(name = "orders") public class Order { }
13. @Entity(name = "orders") public class Order { } insert into orders ...
14. @Entity(name = "orders") public class Order { } em.createQuery("SELECT o FROM Order o")
15. @Entity(name = "orders") public class Order { } em.createQuery("SELECT o FROM orders o")
16. @Entity @Table(name = "orders") public class Order { }
17. MAPPINGS
18. ONE TO ONE @Entity public class Customer { @OneToOne private Address address; } @Entity public class Address { @OneToOne private Customer customer; }
19. ONE TO ONE @Entity public class Customer { @OneToOne private Address address; } @Entity public class Address { @OneToOne(mappedBy = "address") private Customer customer; }
20. ONE TO MANY @Entity public class Customer { @OneToMany private Set<Address> addresses; }
21. ONE TO MANY @Entity public class Customer { @OneToMany @JoinColumn(name = "customer_id") private Set<Address> addresses; }
22. MANY TO MANY @Entity public class Customer { @ManyToMany private Collection<Address> addresses; } @Entity public class Address { @ManyToMany private Collection<Customer> customers; }
23. LAZY LOADING element is loaded only when required proxy by subclassing, but not always needed
24. LAZY LOADING Custom collections PersistentSet PersistentBag PersistentList
25. SET, BAG OR LIST? @OneToMany Set<Product> products;
26. SET, BAG OR LIST? @OneToMany List<Product> products;
27. SET, BAG OR LIST? @OneToMany @OrderColumn List<Product> products;
28. N+1 @Entity public class User { @OneToMany private List<Address> addresses; } List<User> users = em.createQuery("SELECT u FROM User u").getResultList(); for (User user : users) { for (Address address : user.getAddresses()) { ... } }
29. N+1 @Entity public class User { @OneToMany @BatchSize(size = 10) private List<Address> addresses; }
30. N+1 SELECT DISTINCT u FROM User u JOIN FETCH u.addresses
31. HOW TO SAVE EntityManager.persist() EntityManager.merge()
32. OPTIMISTIC LOCKING @Entity public class User { @Version private int version; }
33. OPTIMISTIC LOCKING IN REST NEVER HEARD OF IT
34. IDENTITY EQUALS() AND HASHCODE()
35. BASE CLASS @MappedSuperclass public abstract class BaseEntity implements Serializable { @Id @GeneratedValue private Long id; private String uuid = UUID.randomUUID().toString(); public int hashCode() { return Objects.hash(uuid); } public boolean equals(Object that) { return this == that || that instanceof BaseEntity && Objects.equals(uuid, ((BaseEntity) that).uuid); }
36. CACHING L1 - EntityManager cache / Session cache L2 - EntityManagerFactory cache / SessionFactory cache QueryCache
37. FLUSH MODES MANUAL COMMIT AUTO ALWAYS
38. LEVEL 1 CACHE PITFALLS FLUSH() AND CLEAR()
39. LEVEL 2 CACHE PITFALLS DISTRIBUTED ENVIRONMENT
40. HQL INJECTION String hqlQuery = "SELECT p FROM Product p where p.category = '" + cat + "'"; List<Product> products = em.createQuery(hqlQuery, Product.class) .getResultList();
41. MATERIALS Hibernate logs analysis Hibernate code debugging :-) https://leanpub.com/high-performance-java- persistence https://vladmihalcea.com http://www.jooq.org
42. QUESTIONS?
43. THANKS
44. DYNAMIC UPDATES @Entity @DynamicUpdate public class MyEntity { // ... }
45. DYNAMIC INSERTS @Entity @DynamicInsert public class MyEntity { // ... }