JPA 2与公式派生外键的多对一

Question

Migrating an application from Hibernate 3, trying to map this relation in JPA 2 and not sure how it's handled. In the original application there are these two objects:

TemplateCourse.java

CourseCatCode.java

The TemplateCourse has a many-to-one reference to CourseCatCode . There is no foreign key in TemplateCourse , instead a formula is used to select an ID from a 3rd table based on some criteria, and the corresponding CourseCatCode is joined.

In the hibernate 3 application, the mapping looks like this:

    <many-to-one name="courseCatCode" class="CourseCatCode" not-null="false" insert="false" update="false" lazy="false">
        <formula><![CDATA[
            (
                select
                    smdp_asbch_course.cat_code_id
                from
                    smdp_asbch_course smdp_asbch_course,
                    smdp_template_requirement smdp_template_requirement,
                    smdp_template smdp_template,
                    smdp_degree smdp_degree
                where
                    smdp_degree.degree_id = smdp_template.degree_id
                    and smdp_template.template_id = smdp_template_requirement.template_id
                    and smdp_template_requirement.requirement_id = requirement_id
                    and smdp_asbch_course.school_id = smdp_degree.school_id
                    and smdp_degree.degree_type_code = smdp_asbch_course.degree_type_code
                    and smdp_asbch_course.before_date > SYSDATE
                    and translate(upper(smdp_asbch_course.course_number), 'A-/ ', 'A') = translate(upper(course_number), 'A-/ ', 'A')
            )
        ]]></formula>
    </many-to-one>

Can we do something similar in JPA 2 to map this relation? Our JPA 2 provider is also Hibernate, so if it requires something hibernate specific that is okay.

Answer 1

Have you tried

@JoinFormula(referencedColumnName="cat_code_id", value="(select smdp_asbch_course.cat_code_id " +
                                                       "from smdp_asbch_course " +                                                            smdp_asbch_course, " +
                                                       "smdp_template_requirement smdp_template_requirement, " +
                                                       "smdp_template " +
                                                       "smdp_template, " +
                                                       "smdp_degree smdp_degree " +
                                                       "where smdp_degree.degree_id = smdp_template.degree_id " +
                                                       "  and smdp_template.template_id = smdp_template_requirement.template_id " +
                                                       "  and smdp_template_requirement.requirement_id = requirement_id " +
                                                       "  and smdp_asbch_course.school_id = smdp_degree.school_id " +
                                                       "  and smdp_degree.degree_type_code = smdp_asbch_course.degree_type_code " +
                                                       "  and smdp_asbch_course.before_date > SYSDATE " +
                                                       "  and translate(upper(smdp_asbch_course.course_number), 'A-/ ', 'A') = translate(upper(course_number), 'A-/ ', 'A'))")