Hi everyone
Hi have these tables :
Quote:
CREATE TABLE student (
"std_id" SERIAL NOT NULL,
"std_firstname" VARCHAR(125),
"std_lastname" VARCHAR(125),
....
CONSTRAINT "pk_student" PRIMARY KEY("std_id"),
....
);
CREATE TABLE address (
"adr_id" SERIAL NOT NULL,
"adr_postcode" SMALLINT(4) NOT NULL,
...
CONSTRAINT "pk_address" PRIMARY KEY("adr_id")
);
CREATE TABLE contact (
"con_id" SERIAL NOT NULL,
"con_name" VARCHAR(255),
"adr_id" INTEGER,
...
CONSTRAINT "pk_contact" PRIMARY KEY("con_id"),
CONSTRAINT "fk_contact_address" FOREIGN KEY ("adr_id")
REFERENCES "address"("adr_id") ON DELETE RESTRICT ON UPDATE CASCADE
);
CREATE TABLE student_contact (
"std_id" INTEGER NOT NULL,
"con_id" INTEGER NOT NULL,
"default" BOOLEAN DEFAULT FALSE,
"type" INTEGER NOT NULL,
CONSTRAINT "pk_student_contact" PRIMARY KEY ("std_id", "con_id"),
CONSTRAINT "fk_student_contact_student" FOREIGN KEY ("std_id")
REFERENCES "student"("std_id") ON DELETE RESTRICT ON UPDATE CASCADE,
CONSTRAINT "fk_student_contact_contact" FOREIGN KEY ("con_id")
REFERENCES "contact"("con_id") ON DELETE RESTRICT ON UPDATE CASCADE
);
As you can see I have a N:M relation between
Student and
Contact.
- A
Student can have many
Contacts
- Each
Contacts are represented with a "type"
- Each
Student hold one default
ContactI already have functionnal mappings for
Student and
Contact without these relation (I rarely need a
Student with contacts informations and I'm using
Contact in other relations without
Student). I want to have a mapping who let me retrieve
Student informations and
Contact informations (contact type, and who is the default contact) but I don't know how to make this mapping and hold these values without pollute my objects..
The best solution (in my case) will be to have a
StudentDetails class who maintains a collection (of any type) of
Contacts where I can retrieve "type" informations and the default contact. I have started this mapping :
Quote:
<hibernate-mapping >
<class name="me.StudentDetails" table="student">
<id column="std_id" name="id">
<generator class="sequence">
<param name="sequence">student_std_id_seq</param>
</generator>
</id>
<property column="std_firstname" name="firstName" />
<property column="std_lastname" name="lastName" />
<list name="contactDetails" lazy="false" table="student_contact">
<key column="std_id" />
<list-index column="con_id" />
<many-to-many class="me.StudentDetails.ContactDetails"
column="con_id" />
</list>
</class>
<class name="me.StudentDetails.ContactDetails" table="contact">
<id column="con_id" name="id" >
<generator class="sequence">
<param name="sequence">contact_con_id_seq</param>
</generator>
</id>
<property column="con_name" name="name" />
<many-to-one column="adr_id" name="address" lazy="false"
not-null="false" cascade="save-update" insert="true" />
</class>
</hibernate-mapping>
But I don't know how to retrieve the two relations attributes into my
ContactDetails object.
Of course I can do that in a programmatic way :
Code:
public class StudentDao {
public List<Contact> getContacts(Integer studentId);
public List<Contact> getDefaultContact(Integer studentId);
}
But I'm sure that someone here can help me and give me a better solution..
Thanks
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