Petr V. schrieb:
> I want to have two way relationship like Teacher contains reference of
> Student and Student contains reference of Teacher. Is it even possible
> in iBatis ?
>
> class Teacher {
> Student sid;
> ....
> }
>
> class Student {
> Teacher teacher;
> ....
> }
>
>
> I wrote the following SQL config file and as expected I got stack over
> flow due to recursion.(Map referring each other)
>
> <resultMap id="TeacherResultMap99" class="Teacher" groupBy="id" >
> <result property="id" column="tea_id"/>
> <result property="name" column="tea_name" />
> <result property="sid" resultMap="JOB.StudentResultMap99"/>
> </resultMap>
>
> <resultMap id="StudentResultMap99" class="Student" >
> <result property="id" column="stu_id"/>
> <result property="name" column="stu_Name"/>
> <result property="teacher" resultMap="JOB.TeacherResultMap99"/>
> </resultMap>
>
>
> <select id="findStudent" parameterClass="int"
> resultMap="StudentResultMap99">
> select t.id as tea_id , t.name as tea_name , s.id as stu_id, s.name
> as stu_Name , s.tid as stu_tid from Teacher t left join student s on
> t.id = s.tid where s.id = #value#
> </select>
SELECT
t.id AS tea_id,
t.name AS tea_name,
s.id AS stu_id,
s.name AS stu_name,
s.tid AS stu_tid
FROM teacher t
LEFT JOIN student s ON t.id = s.tid
WHERE s.id = #value#
I don't understand, why you use a LEFT JOIN to table student. You
provide the ID of the student as a parameter. If there exists a
corresponding row, you get a result, if not, you don't. You can use a
RIGHT JOIN instead, if there exist students without teacher.
If you have a real 1 to 1 relationship, omit the groupBy attribut and
the result element for property "sid". Otherwise use List<Student> in
class Teacher.
StudentDAOImpl
{
public Student findStudent(Integer id)
{
return (Student)
getSqlMapClientTemplate().queryForObject("<NAMESPACE>.findStudent", id)
}
}
Somewhere in your business code you can write something like that:
Integer id = ...
Student student = this.studentDAO.findStudent(id);
if (student != null)
{
Teacher teacher = student.getTeacher();
if (teacher != null)
{
teacher.setStudent(student);
}
}
