JPA:JpaRepository中的实体和想要查询的实体不对应怎么办？

Posted 2022-02-22 长不大的大灰狼

JPA:JpaRepository中的实体和想要查询的实体不对应怎么办？

每个实体要都要有一个对应的XXXRepository来执行CRUD操作的。

比如现有一个School实体，以及SchoolRepository 接口：

SchoolRepository extends JpaRepository<School, Integer>

如果查询结果是学校，都是没有问题的。

SchoolRepository extends JpaRepository<School, Integer>
	School findByStudentId();

但是，如果要查询出相应的老师呢？

SchoolRepository extends JpaRepository<School, Integer>
	@Query(value="select t.* from School s inner join 
teacher t on t.s_id = s.id ",nativeQuery=true)
List<Teacher> findTeachers();

很显然这样会报错，Failed to convert from type [XXXX] to type [XXXX]。

class Teacher
 private String id;
 private String name;

为了解决这个问题：

SchoolRepository extends JpaRepository<School, Integer>
	@Query(value="select t.id id,t.name name from School s inner join 
teacher t on t.s_id = s.id ",nativeQuery=true)
List<Map<String,Object>> findTeachers();

public class SchoolService
	@Autowired
	SchoolRepository  schoolRepostitory;
	
	public List<Teacher> findTeachers()
		List<Map<String,Object>> map = schoolRepostitory.findTeachers()
		List<Teacher> list = convertToTeacher(map);
		return list;
	

	public List<Teacher> convertToTeacher(List<Map<String,Object>> maps)
		return maps.stream().map(cur->new Teacher(
		cur.get(id),
		cur.get(name)
		)).collect(Collectors.toList());