Spring Data JPA创建查询的各种方法

1. 创建一个接口，并继承Repository类，然后通过解析方法的名称创建查询

例如下面的代码

public interface UserRepository extends Repository {
    List findByEmailAddressAndLastname(String emailAddress, String lastname);
}

findByEmailAddressAndLastname会转换为以下的查询：select u from User u where u.emailAddress = ?1 and u.lastname = ?2 ，因为JPA模块支持将查询从方法名称中解析。

---

下表描述了JPA支持的关键字以及包含该关键字的方法转换：

关键词	示例	等效JPQL的片段
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or 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 ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection 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)

2. 使用JPA命名查询

可以使用基于XML或者基于注解的方式配置查询，两者是等效的

• 基于XML的配置

  select u from User u where u.lastname = ?1

• 基于注解的配置

@Entity
@NamedQuery(name = "User.findByEmailAddress",
  query = "select u from User u where u.emailAddress = ?1")
public class User {

}

然后声明接口，要允许执行以上的命名查询，需指定UserRepository如下

public interface UserRepository extends JpaRepository {

  List findByLastname(String lastname);

  User findByEmailAddress(String emailAddress);
}

3. 运用@Query注解

• 一般查询

public interface UserRepository extends JpaRepository {

  @Query("select u from User u where u.emailAddress = ?1")
  User findByEmailAddress(String emailAddress);
}

• 使用命名参数

public interface UserRepository extends JpaRepository {

  @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SpEL表达式

@Entity
public class User {

  @Id
  @GeneratedValue
  Long id;
  String lastname;
}

public interface UserRepository extends JpaRepository {

  @Query("select u from #{#User} u where u.lastname = ?1")
  List findByLastname(String lastname);
}

---

参考资料：Spring Data JPA - 参考文档