SELECT * FROM classes
SELECT * FROM student WHERE cid=#{cid}

public interface StudentMapper {
    //根據cid查詢student表
    @Select("SELECT * FROM student WHERE cid=#{cid}")
    public abstract List<Student> selectByCid(Integer cid);
}

public interface ClassesMapper {
    //查詢全部
    @Select("SELECT * FROM classes")
    @Results({
            @Result(column = "id",property = "id"),
            @Result(column = "name",property = "name"),
            @Result(
                    property = "students",  // 被包含對象的變量名
                    javaType = List.class,  // 被包含對象的實際數(shù)據類型
                    column = "id",          // 根據查詢出的classes表的id字段來查詢student表
                    /*
                        many、@Many 一對多查詢的固定寫法
                        select屬性：指定調用哪個接口中的哪個查詢方法
                     */
                    many = @Many(select = "com.yyl.one_to_many.StudentMapper.selectByCid")
            )
    })
    public abstract List<Classes> selectAll();
}

public class Test01 {
    @Test
    public void selectAll() throws Exception{
        //1.加載核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.獲取SqlSession工廠對象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通過工廠對象獲取SqlSession對象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.獲取ClassesMapper接口的實現(xiàn)類對象
        ClassesMapper mapper = sqlSession.getMapper(ClassesMapper.class);
        //5.調用實現(xiàn)類對象中的方法，接收結果
        List<Classes> list = mapper.selectAll();
        //6.處理結果
        for (Classes cls : list) {
            System.out.println(cls.getId() + "," + cls.getName());
            List<Student> students = cls.getStudents();
            for (Student student : students) {
                System.out.println("\t" + student);
            }
        }
        //7.釋放資源
        sqlSession.close();
        is.close();
    }
}