Mybatis如何实现对象的更新？

现在有这样两张表：

CREATE TABLE STUDENTS
(
stud_id int(11) NOT NULL AUTO_INCREMENT,
name varchar(50) NOT NULL,
email varchar(50) NOT NULL,
phone_number varchar(15) NULL,
dob date DEFAULT NULL,
address_id int(11) NOT NULL,
PRIMARY KEY (stud_id)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
/*Sample Data for the students table */
insert into students(stud_id,name,email,dob,address_id)
values (1,'Student1','student1@gmail.com','1983-06-25',1);
insert into students(stud_id,name,email,dob)
values (2,'Student2','student2@gmail.com','1983-06-25',2);
CREATE TABLE ADDRESS
(
address_id int(11) NOT NULL AUTO_INCREMENT,
city varchar(50) NOT NULL,
state varchar(50) NOT NULL,
PRIMARY KEY (address_id)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
insert into  address(city,state) values('北京','北京');
insert into  address(city,state) values('上海','上海');

对于关联查询，是比较简单的：

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- type 就是java类型  resultMap就是java类属性名与表字段名的映射-->
<mapper namespace="com.mybatis.mappers.StudentMapper">

<resultMap type="com.mybatis.mappers.Student" id="StudentResult">
<id property="studId" column="stud_id" />
<result property="name" column="name" />
<result property="email" column="email" />
<result property="dob" column="dob" />
<result property="address.addressId" column="address_id"/>
<result property="address.city" column="city"/>
<result property="address.state" column="state"/>
</resultMap>

<select id="selectStudents" resultMap="StudentResult">
select students.*,address.* from   students left outer join address on students.address_id=address.address_id
</select>

</mapper>

这样，就能实现面向对象式的查询。

但是，如何实现面向对象式的更新呢？
比如,外在的API接口是如下的：

@Test
     public  void  testStudent() throws IOException{
        
        
        InputStream    inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory    factory = new
        SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session=    factory.openSession();
        session.getConnection();
        /*
         * XML文件与Mapper类的名字保持一致，就能自动关联映射。
         * 
         */
        StudentMapper mapper = session.getMapper(StudentMapper.class);
    List<Student>  students=     mapper.selectStudents();
    
    for (Student student : students) {
        //更新了Address：
        student.getAddress().setCity("西安");
//直接实现保存：更改的实际上是Address这个表：
        mapper.save(student);
    }
     }

---

想了一下，这种需求好像在关系型数据库中间比较奇葩。。。在nosql当中倒是比较常见。