Definition and examples about Persistence in Java Example Structures to develop with persistence programming java

1. What is
Persistence
in Java
김 병 부 (Benjamin Kim)
byungboor@naver.com
http://myboor.tistory.com

2. About what?
• History
• JPA Features
• Persistence
• ORM
• JPA CRUD
• JPA Entity LifeCycle
• Why Hibernate?
• Spring Data JPA

3. Market Situation

4. Market Situation

5. Hibernate VS MyBatis VS JDBC
Criteria JDBC MyBatis Hibernate
Learning Curve Simple to learn Simple to learn Many aspects to learn
Work in data centric env Good, mapping efforts
exits
Naturally fits Mapping issues, low
performance
Work in obj centric env Major mapping efforts Good, limited feature
amount
Naturally fits
Object Mapping Manual, hard to support Maps methods to
statements
Transparent persistence
Query Language Native SQL Native SQL HQL, Native SQL,
Criteria API
Caching Poor,
manual or 3rd party
Good customization 3 level, advanced
customization

6. Hibernate VS MyBatis VS JDBC Performance test
Test JDBC MyBatis Hibernate
Read 5k Employees
0.51 0.77 8.09
Create and Insert 10
Employees
0.73 0.9 0.67
Update 10 Employees
0.58 0.55 0.7
Update 10 Employee
Addresses
0.28 0.2 0.41
Cascade delete of 10
Employees
2.25 0.71 0.79

7. History
EJB-Entity Bean
Hibernate
JPA v1.0 (2006. 5) JPA v2.0 (2009.12) JPA v2.1 (2013)
Spring Data
Spring-Data-JPA

8. History
JPA
OpenJPA EclipseLink Hibernate

9. JPA Features
• JPA 2.0
– Expanded object-relational mapping functionality
– Criteria query API
– Query Hints 표준
– DDL 생성 metadata 표준
– Validation
– Shared Object cache support
• JPA 2.1
– Converters - allowing custom code conversions between database and object types.
– Criteria Update/Delete - allows bulk updates and deletes through the Criteria API.
– Stored Procedures
– Schema Generation
– Entity Graphs - allow partial or specified fetching or merging of objects.
– JPQL/Criteria 강화 - arithmetic sub-queries, generic database functions, join ON clause, TREAT option.

10. Persistence
• Persistence
– 사전적 의미 : 고집, 지속, 영속성 or 영속화
– 보편적 의미의 Persistence는 Application이나 Object가 수명을 다했을 때도, Object의 데이터가 저장되
는 것을 의미한다.
– 저장소 : DBMS, File 등등
• Persistence Object in JAVA
– 이미 익숙한 객체
– POJO 기반의 클래스 객체
– Java Bean Style – private 속성, getter/setter
– Persistence Object = Table의 1개 Row

11. ORM
• ORM (Object-Relational Mapping)
– 관계형 데이터와 객체 데이터를 서로 맵핑 시키는것.
– Persistence Object 를 처리 해주는 것.
– E.g. Hibernate F/W
• What is difference between Mybatis and Hibernate
– Database-centric VS Object-centric
– Mybatis is focusing on SQL Mapping Persistent F/W
– Hibernate is focusing on ORM framework

12. JPA CRUD
• EntityManager
– Application-managed EntityManager, Container-managed EntityManager
– DB에서 Entity 와 관련된 작업 API(CRUD)를 제공한다.
– Create
– Read, Update, Delete
@PersistenceContext
private EntityManagerFactory emf;
// ...
EntityManager em = emf.createEntityManager();
Customer customer = new Customer(id, name, address);
em.persist(customer);
Customer customer = em.find(Customer.class, id); // Read
customer.setAddress(“newAddressString”); // Update
em.remove(customer) // Delete

13. JPA Entity LifeCycle
• NEW
– Entity 인스턴스만 생성된 상태 – DB와 연결이 없다.
• Managed
– Persistence Context에 의해서 관리되는 상태
– Entity 내부 속성값이 바뀌면 DB에 반영 (Update됨)
• Detached
– Entity Instance 가 Persistence Context 에 의해서 관리되지 않는 상태
– EntityManager의 merge() 로 Managed 상태로 천이 가능
• Removed
– DB에서 Entity 가 삭제되는 상태

14. Why Hibernate?
• Advantage
– DDD
– 생산성
– 이식성
– 트렌드
• Disadvantage
– 성능에 대한 부담감
– 복잡한 Domain 구조에서의 부족한 설계 경험
– 너무나 익숙한 SQL
그럼에도 불구하고 Hibernate.

15. Why Hibernate?
• Hibernate supported Databases
– MySQL (innoDB, MyISAM)
– Oracle (any version)
– DB2
– PostgreSQL
– Informix
– H2
– DERBY
– SQL_SERVER
– SYBASE

16. Spring Data JPA
• http://projects.spring.io/spring-data/
• One of sub project of Spring-DATA
– MongoDB, NEO4J, REDIS, SOLAR, HADOOP, ElasticSearch, CouchBase, Cassandra,
DynamoDB, JDBC Extentions
• Anti - Boiler-plate structure
– 정해진 규칙에 따라 인터페이스 생성시 단순 노동을 줄일 수 있음

17. Spring Data JPA
• In case of Mybatis, to develop User domain
– UserMapper.xml
• CRUD Queries and Another Search Queries
– UserMapper.java interface
• CRUD Methods and Another Search Methods mapped with UserMapper.xml
– UserDao.java interface
• CRUD and Search Methods for DAO Layer
– UserDaoImpl.java class
• CRUD and Search implementation Methods
– UserValue domain class
• In case of Hibernate, to develop User domain
– Only required UserRepository similar to UserDao interface. That’s all
– User domain class with some annotation

18. Spring Data JPA
• Entity

19. Spring Data JPA
• Repository
– org.springframework.data.Repository Interface in Spring-Data-JPA

20. Spring Data JPA
• Repository Naming Rule
Operation Rule
Read T findOne(ID primaryKey)
List<T> findAll()
List<T> findByDeptName(String deptName)
List<T> findByDeptNameAndPhone(String deptName, phone)
List<T> findByPhoneIn(Collection<String> phones)
List<T> findByNameStartingWith(String name)
List<T> findByNameEndingWith(String name)
List<T> findByNameIgnoreCase(String name)
Long count()
Long countByDeptName(String deptName)
Create T save(T t)
Delete void delete(Long id);
void delete(T t);
void delete(List<T> entities);
void deleteAll();

21. Spring Data JPA
• 검색조건 Specification
– org.springframework.data.jpa.domain.Specification
• 정렬조건
– org.springframework.data.domain.Sort
• 페이징 처리
– org.springframework.data.domain.Pageable

22. Spring Data JPA
<<interface>>
Repository
<<interface>>
CrudRepository
<<interface>>
PagingAndSortingRepository
<<interface>>
JpaRepository
<<interface>>
JpaSpecificationExecutor

23. Development Stack

24. Reference Link
• http://en.wikipedia.org/wiki/Java_Persistence_API
• http://www.javajigi.net/pages/viewpage.action?pageId=5924
• http://www.youtube.com/watch?v=OOO4H3BAetU
• http://hibernate.org/orm/what-is-an-orm/
• http://www.slideshare.net/iwish1hadanose/hibernate-vs-my-batis-vs-jdbc-is-there-a-
silver-bullet
• http://zeroturnaround.com/rebellabs/