===============
MyBatis回填主键
===============

public interface StudentDao {
    ...
    // 增加学生返回标识
    public int addHasId(Student student);
    ...
}

<mapper>                                将生成的主键回填到
    ...                            _____实体对象的id属性中_____
    <!-- 增加学生返回标识 -->     |                            v
    <insert id="addHasId" useGeneratedKeys="true" keyProperty="id">
        insert into t_student(number, name, gender, age)
        values(#{number}, #{name}, #{gender}, #{age})
    </insert>
    ...
</mapper>

public class StudentDaoTest {
    ...
    // 测试增加学生返回标识
    @Test
    public void testAddHasId() {
        // SQL会话工厂建造器
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();

        try {
            // SQL会话
            SqlSession session = new SqlSessionFactoryBuilder()
                .build(Resources.getResourceAsStream("mybatis-config.xml"))
                .openSession();
            // 数据访问对象
            StudentDao dao = session.getMapper(StudentDao.class);

            // 学生实体
            Student student = new Student(0, "1004", "赵云", "男", 20);
            // 增加学生返回标识
            int rows = dao.addHasId(student);
            // 打印受影响的行数
            System.out.println(rows);
            // 打印新增学生标识
            System.out.println(student.getId());
            // 提交事务
            session.commit();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
    ...
}

例程：HelloMyBatis