Spring Data JPA @NamedQuery用法如下。
@NamedQuery與定義在Repository方法上的@Query類似，都可對Repository方法自訂JPQL查詢。
@NamedQuery掛在@Entity類別前，可以直接撰寫JPQL查詢語言及對應的Repository查詢方法名稱，當呼叫Repository查詢方法時會以@NamedQuery定義的JPQL查詢。
例如下面是entity類Employee。類別名稱前加上@NamedQuery並在query定義EmployeeRepository.findByAge(int age)查詢時使用JPQL。對應的呼叫方法名稱設定在屬性name，要以entity類的名稱開頭後接點號再接方法名。
Employee
package com.abc.demo.entity;
import javax.persistence.*;
import java.io.Serializable;
@NamedQuery(
name = "Employee.findByAge",
query = "SELECT e FROM Employee e WHERE e.age = ?1"
)
@Entity
public class Employee implements Serializable {
private static final Long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
private String name;
private Integer age;
// getters, setters, equals() and hashCode()
}
Employee的Repository類EmployeeRepository。
EmployeeRepository
package com.abc.demo.repository;
import com.abc.demo.entity.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long> {
List<Employee> findByAge(int age); // 會以Employee的@NamedQuery.query設定的JPQL查詢
}
產生的SQL如下：
select employee0_.id as id1_1_, employee0_.age as age2_1_, employee0_.name as name3_1_ from employee employee0_ where employee0_.age=?
也可以改用名稱參數(Named Parameters)如下：
Employee
@NamedQuery(
name = "Employee.findByAge",
query = "SELECT e FROM Employee e WHERE e.age = :age"
)
@Entity
public class Employee implements Serializable {...}
EmployeeRepository
@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long> {
List<Employee> findByAge(@Param("age") int age); // named parameters
}
@NamedQuery可設定多個。
Employee
@NamedQuery(
name = "Employee.findByAge",
query = "SELECT e FROM Employee e WHERE e.age = :age"
)
@NamedQuery(
name = "Employee.findByName",
query = "SELECT e FROM Employee e WHERE e.name = :name"
)
@Entity
public class Employee implements Serializable {...}
JPA 2.2及Hibernate 5.2以前若有多個@NamedQuery要用@NamedQueries包起。
Employee
@NamedQueries(
{
@NamedQuery(
name = "Employee.findByAge",
query = "SELECT e FROM Employee e WHERE e.age = :age"
),
@NamedQuery(
name = "Employee.findByName",
query = "SELECT e FROM Employee e WHERE e.name = :name"
)
}
)
@Entity
public class Employee implements Serializable {...}
若要用原生SQL則改用@NamedNativeQuery。
Employee
@NamedNativeQuery(
name = "Employee.findByAge",
query = "SELECT * FROM employee WHERE age = :age", // native sql
resultClass = Employee.class
)
@Entity
public class Employee implements Serializable {...}
查詢的SQL如下：
SELECT * FROM employee WHERE age = ?
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