I'm having a problem where the related table id fields return 'null' from my domain objects when using inheritance. Here is an example:
In /src/groovy/
BaseClass1.groovy
class BaseClass1 {
Long id
static mapping = {
tablePerConcreteClass true
}
}
BaseClass2.groovy
class BaseClass2 extends BaseClass1 {
String someOtherProperty
static constraints = {
someOtherProperty(maxSize:200)
}
static mapping = BaseClass1.mapping
}
In /grails-app/domain
ParentClass.groovy
class ParentClass extends BaseClass2 {
ChildClass myChild
static mapping = BaseClass2.mapping << {
version false
}
}
ChildClass.groovy
class ChildClass extends BaseClass1 {
String property
static mapping = BaseClass1.mapping
}
The problem appears here:
SomeotherCode.groovy
print parentClassInstance.myChild.id // returns the value
print parentClassInstance.myChildId // returns null
Any ideas what might be going on to get those dynamic properties to break like this?
After debugging into the get(AssociationName)Id source, I found the following: The handler for this is:
GrailsDomainConfigurationUtil.getAssociationIdentifier(Object target, String propertyName,
GrailsDomainClass referencedDomainClass) {
String getterName = GrailsClassUtils.getGetterName(propertyName);
try {
Method m = target.getClass().getMethod(getterName, EMPTY_CLASS_ARRAY);
Object value = m.invoke(target);
if (value != null && referencedDomainClass != null) {
String identifierGetter = GrailsClassUtils.getGetterName(referencedDomainClass.getIdentifier().getName());
m = value.getClass().getDeclaredMethod(identifierGetter, EMPTY_CLASS_ARRAY);
return (Serializable)m.invoke(value);
}
}
catch (NoSuchMethodException e) {
// ignore
}
catch (IllegalAccessException e) {
// ignore
}
catch (InvocationTargetException e) {
// ignore
}
return null;
}
It threw an exception on the related class (value.getClass().getDeclaredMethod), saying NoSuchMethod for the method getId(). I was unable to remove the id declaration from the base class without Grails complaining that an identifier column was required. I tried marking id as public and it also complained that it wasn't there. So, I tried this
BaseClass {
Long id
public Long getId() { return this.@id }
}
and things worked on some classes, but not on others.
When I removed the ID declaration, I go an error: "Identity property not found, but required in domain class". On a whim, I tried adding @Entity to the concrete classes and viola! everything started working.
class BaseClass {
//Don't declare id!
}
@Entity
class ParentClass {}
@Entity
class ChildClass {}
I still think it is a grails bug that it needs to be added, but at least it is easy enough to work around.
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