写一个接口，根据老师id查询他的学生，从controller到service到serviceimpl到mapper

好的，我来为您编写这个接口，具体步骤如下：

1. 编写Controller层接口

@RestController
@RequestMapping("/teacher")
public class TeacherController {
    @Autowired
    private TeacherServiceImpl teacherService;

    @GetMapping("/{teacherId}/students")
    public List<Student> getStudentsByTeacherId(@PathVariable Long teacherId) {
        return teacherService.getStudentsByTeacherId(teacherId);
    }
}

2. 编写Service层接口

public interface TeacherService {
    List<Student> getStudentsByTeacherId(Long teacherId);
}

3. 编写Service层实现类

@Service
public class TeacherServiceImpl implements TeacherService {
    @Autowired
    private TeacherMapper teacherMapper;

    @Override
    public List<Student> getStudentsByTeacherId(Long teacherId) {
        return teacherMapper.selectStudentsByTeacherId(teacherId);
    }
}

4. 编写Mapper接口

@Mapper
public interface TeacherMapper {
    @Select("SELECT s.* FROM student s INNER JOIN teacher_student ts ON s.id = ts.student_id WHERE ts.teacher_id = #{teacherId}")
    List<Student> selectStudentsByTeacherId(@Param("teacherId") Long teacherId);
}

在上面的代码中，我们编写了一个根据老师id查询学生的接口，通过Controller层调用Service层，再由Service层调用Mapper层，最终查询出对应的学生信息。具体实现中，我们使用了Mybatis的注解方式编写了SQL语句，使用了Mapper的select方法查询出对应的学生信息。