Spring Data JPA相关接口介绍及简单应用

Repository接口及其子接口介绍

Repository接口

接口定义：

public interface Repository<T, ID extends Serializable> {
}

Repository接口是一个空接口，这个接口主要作为一个标记接口来捕获类型的工作，并帮助你发现继承这个接口的接口。

CrudRepository接口

CrudRepository接口继承Repository接口，实现了CRUD相关方法：

public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> {
    <S extends T> S save(S var1);

    T findOne(ID var1);

    boolean exists(ID var1);

    Iterable<T> findAll();

    long count();
  
  	void delete(T entity);
  
  	// … more functionality omitted.
}

PagingAndSortingRepository接口

PagingAndSortingRepository接口继承CrudRepository接口，实现了分页排序相关的方法：

public interface PagingAndSortingRepository<T, ID extends Serializable> 
    extends CrudRepository<T, ID> {
    
    Iterable<T> findAll(Sort var1);

    Page<T> findAll(Pageable var1);
}

JpaRepository接口

JpaRepository接口继承PagingAndSortingRepository接口，实现了JPA规范的相关方法：

public interface JpaRepository<T, ID extends Serializable> 
	extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
	
    List<T> findAll(Sort var1);

    <S extends T> List<S> save(Iterable<S> var1);

    void flush();

    <S extends T> S saveAndFlush(S var1);

    void deleteInBatch(Iterable<T> var1);
    
    // … more functionality omitted.
}

使用方法命名规则查询

Spring Data JPA支持以特定的方法命名规则来生成查询。

下面是对JPA支持的关键字的概述，以及包含该关键字翻译成的sql片段。

Keyword	Sample	JPQL snippet
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
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1
Containing	findByFirstnameContaining	… where x.firstname like ?1
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)

In和NotIn可以将Collection的任何子类作为参数以及数组或可变参数。

例子：

public interface UserRepository extends Repository<User, Long> {
  
	List<User> findByEmailAddressAndLastname(String emailAddress, String lastname);
	// where name like ?% and age <?
	List<User> findByNameStartingWithAndAgeLessThan(String name, Integer age);
	// where name in (?,?....) or age <?
	List<User> findByNameInOrAgeLessThan(List<String> names, Integer age);
}

使用按照方法命名规则，有弊端：

• 方法名会比较长： 约定大于配置
• 对于一些复杂的查询，是很难实现

使用@Query注解

对查询方法进行注释的查询优先于使用@NamedQuery定义的查询或者在orm.xml中声明的命名查询。

public interface UserRepository extends JpaRepository<User, Long> {

  //占位符的方式
  @Query("select u from User u where u.firstname = ?1 or u.lastname = ?2")
  User findByLastnameOrFirstname(String lastname, String firstname);
  
  //命名参数的方式
  @Query("select u from User u where u.firstname = :firstname or u.lastname = :lastname")
  User findByLastnameOrFirstname(@Param("lastname") String lastname,
                                 @Param("firstname") String firstname);
  
  //使用@Query手动定义查询,允许在查询定义内定义高级LIKE表达式。
  @Query("select u from User u where u.firstname like %?1")
  List<User> findByFirstnameEndsWith(String firstname);
}

@Query注释允许通过将nativeQuery设置为true来执行原生sql查询。

public interface UserRepository extends JpaRepository<User, Long> {

  @Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?1", nativeQuery = true)
  User findByEmailAddress(String emailAddress);
}

@Query、@Modifying、@Transactional综合使用

使用@Query执行更新操作需要配合@Modifying注解和@Transactional注解。

事务一般在service层控制。

interface UserRepository extends Repository<User, Long> {
  
  @Modifying
  @Query("update User u set u.firstname = ?1 where u.lastname = ?2")
  int setFixedFirstnameFor(String firstname, String lastname);
  
  @Modifying
  @Query("delete from User u where user.role.id = ?1")
  void deleteInBulkByRoleId(long roleId);
}

public class UserService {
  
  @Autowired
  private UserRepository userRepository;
  
  @Transactional
  public int setAge(Integer age, Integer id){
     return userRepository.setFixedFirstnameFor(age, id);
  }
}

参考链接

https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#reference