什么是Spring Data JPA？
Spring Data JPA是Spring Data系列中的重要一员，他帮助我们能够更简单的实现基于JPA的数据访问。免去写CRUD的痛苦。
还记得当年写hibernate的CRUD吗？
public class AppTest {
private static final String PERSISTENCE_UNIT_NAME = "psunit1";
private static EntityManagerFactory factory;
public static void main(String[] args) {
factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
Product product = new Product();
product.setProductName("JPA 2.1 Book");
product.setProductDescription("This is the latest book on JPA 2.1");
product.setStockQty(100.00);
product.setPrice(95.99);
em.persist(product);
em.getTransaction().commit();
em.close();
}
}
如果换成JPA呢？
interface PersonRepository extends CrudRepository<User, Long> {
Person save(Person person);
}
简单到想哭 （T T）
只要继承Spring Data JPA的Repository，然后按照Spring Data JPA的要求写方法名，一切都妥妥的了。
| Keyword | 例子 | sql |
|---|---|---|
| And | findByLastnameAndFirstname | … where x.lastname = ?1 and x.firstname = ?2 |
| Or | findByLastnameOrFirstname | … where x.lastname = ?1 or x.firstname = ?2 |
| Is,Equals | findByFirstname,findByFirstnameIs,findByFirstnameEquals | … where x.firstname = ?1 |
| Between | findByStartDateBetween | … where x.startDate between ?1 and ?2 |
| LessThan | findByAgeLessThan | … where x.age < ?1 |
| LessThanEqual | findByAgeLessThanEqual | … where x.age <= ?1 |
| GreaterThan | findByAgeGreaterThan | … where x.age > ?1 |
| GreaterThanEqual | findByAgeGreaterThanEqual | … where x.age >= ?1 |
| After | findByStartDateAfter | … where x.startDate > ?1 |
| Before | findByStartDateBefore | … where x.startDate < ?1 |
| IsNull | findByAgeIsNull | … where x.age is null |
| IsNotNull,NotNull | findByAge(Is)NotNull | … where x.age not null |
| Like | findByFirstnameLike | … where x.firstname like ?1 |
| NotLike | findByFirstnameNotLike | … where x.firstname not like ?1 |
| StartingWith | findByFirstnameStartingWith | … where x.firstname like ?1 (parameter bound with appended %) |
| EndingWith | findByFirstnameEndingWith | … where x.firstname like ?1 (parameter bound with prepended %) |
| Containing | findByFirstnameContaining | … where x.firstname like ?1 (parameter bound wrapped in %) |
| OrderBy | findByAgeOrderByLastnameDesc | … where x.age = ?1 order by x.lastname desc |
| Not | findByLastnameNot | … where x.lastname <> ?1 |
| In | findByAgeIn(Collection<Age> ages) | … where x.age in ?1 |
| NotIn | findByAgeNotIn(Collection<Age> ages) | … where x.age not in ?1 |
| True | findByActiveTrue() | … where x.active = true |
| False | findByActiveFalse() | … where x.active = false |
| IgnoreCase | findByFirstnameIgnoreCase | … where UPPER(x.firstame) = UPPER(?1) |
Spring Data JPA除了能够支持方法名的方式，还可以通过加注解的方式来实现。
- 使用HQL
public interface UserRepository extends JpaRepository<User, Long> {
@Query("select u from User u where u.emailAddress = ?1")
User findByEmailAddress(String emailAddress);
}
- 使用native(SQL)
public interface UserRepository extends JpaRepository<User, Long> {
@Query(value = "SELECT * FROM USERS WHERE LASTNAME = ?1",
countQuery = "SELECT count(*) FROM USERS WHERE LASTNAME = ?1",
nativeQuery = true)
Page<User> findByLastname(String lastname, Pageable pageable);
}
Transactional
Spring有自己的事务注解。
@Transactional(readOnly = true)
public interface UserRepository extends JpaRepository<User, Long> {
List<User> findByLastname(String lastname);
@Modifying
@Transactional
@Query("delete from User u where u.active = false")
void deleteInactiveUsers();
}
Transectional 注解主要有4个重要的属性
- Isolation
- Propagation
- Timeout
- Read-only状态
