Grails problem persisting data in join tables for many-to-many relationships

Question

I am having problems persisting domain objects where I have a many-to-many relationship with a join table

class A{

String name
static hasMany = [bs:B]

}


class B{

String surname
static belongsTo=A
static hasMany=[as:A]

}

A a = new A(name:'Test')
B b = new B(surname:'user')

a.addToBs(b)
a.save(flush:true)

Then what I would expect to see is the following

Table A                      Table AB                  Table B
id    name                 a_id     b_id               id   surname
1      Test                 1         1                 1    User

However, the data only persists into table A.

Does anybody know what I am doing wrong ?

thanks

Answer 1

I have found this link which is shows a clear way of mapping many to many relationships

http://chrisbroadfoot.id.au/2008/07/19/many-to-many-relationship-mapping-with-gorm-grails

I still havent been able to get it working the way that I want to at the moment

Answer 2

I tried imitating your code and cascading works for me.

Class A:

package searcher

class A {
    String name
    static hasMany = [bs:B]

    static constraints = {
    }

    public String toString() {
        def s = "Name: $name\n Bs: "
        bs.each {
            s = "$s $it "
        }
        return s
    }
}

Class B:

package searcher

class B {

    String surname
    static belongsTo = A
    static hasMany = [as:A]

    static constraints = {
    }
}

Controller Source:

package searcher

class ManyController {

    def ab = {

        A a = new A(name:'Test')
        B b = new B(surname:'user')
        a.addToBs(b)
        a.save(flush:true)

        render A.list()
    }
}

Produces output:

[Name: Test Bs: searcher.B : 1 ]

I didn't run into the problem you did, but I did have some initial trouble that was fixed by doing a grails clean. Have you tried a variety of database configurations? I was just using an in memory hsqldb set to create-drop. If you're using a DBMS that I happen to have installed I'll try pointing it to another database and giving it a whirl.