Grails findBy belongsTo gives JdbcSQLException - grails

Question

Say, for a system, I had Student and User objects, like so:
User {
}
Student {
User user //not nullable
static belongsTo = [User]
}
Teacher {
static belongsTo = [user:User]
}
I have a lot of code written against these models, and plenty of dynamic finders in it
def u1 = new User().save( flush: true)
new Student( user: u1 ).save( flush: true)
...
def s = Student.findByUser( springSecurityService.currentUser)
//s can be null
def t = Teacher.findByUser( springSecurityService.currentUser)
//t can be null
if( s != null)
//do something with 's'
if( t != null)
//do something with 't'
...
And this all worked fine. But I wanted to update my domain model to add cascading access from User to Student. So I did:
User {
Student student //nullable
}
And I would save a user like this:
new User( student: new Student() ).save( flush: true)
But the problem is, when I try to access 's' like I did above.
If the Student.findByUser can find one such student, then it works.
But if it should return null, it gives an error instead.
def s = Student.findByUser( springSecurityService.currentUser)
will result in:
org.h2.jdbc.JdbcSQLException
Parameter #2 is not set; SQL statement:
select this_.id as id18_0_, this_.version as version18_0_, from student this_ where this_.id=? limit ? [90012-173]
I know I can access the student object through the user object like user.student, but I would like to be able to keep the existing code as it is.
I've seen this thread, and it had a similar problem, but no resolution grails email list
Is this a bug? What can I do to get around it? Am I not setting up my domain models properly?
Thanks

Answer 1

As an alternative, you could try something like this using hasOne instead of belongsTo.
class User {
static hasOne = [student:Student, teacher:Teacher]
static constraints = {
student unique:true, nullable: true
teacher unique:true, nullable: true
}
}
class Student {
User user
}
class Teacher {
User user
}
It still cascades and appears to handle null searches fine.