[OJB] Issue #OJB242 modified

[Jakob Braeuchi <jb...@hotmail.com>]

You can view the issue detail at the following URL:

    http://nagoya.apache.org/scarab/issues/id/OJB242

Type
 Defect

Issue ID
 OJB242 (Cannot resolve multiple attributes in a single criteria or column)

Modified by
 Jakob Braeuchi
 brj (jbraeuchi@hotmail.com)

The following modifications were made to this issue:
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Resolution set to "Later"

Reason:
should be fixed with OJB244

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Re: How do you map a reference to an interface-backed class? (non-trivial)

[Thomas Dudziak <to...@first.fhg.de>]

Andrew Clute wrote:

> I have looked at all of the examples, I can't seem to make heads or 
> tails of how to handle my situation. I want to map a class that has a 
> reference to an object, that can one of many different objects, that all 
> implement the same interface.
> 
> Example
> 
> Interface A{
> 
> }
> 
> class B implements A
> {}
> 
> class C implements A
> {}
> 
> class Z
> {
>     private A myA;
> }
> 
> So, in this case, how do I map class Z since it's member variable is of 
> Type A, but I want the concrete object, either of Type B or C to be 
> filled in.
> 
> Seems like there is no known strategy to do this: "Using Interfaces With 
> OJB" talks about a similar situation, but assumes that there is only one 
> concrete class that can be instantiated for the reference (the 
> factory-method assumes that it will only return one concrete class type).
> 
> Seems like I need a combination of the Interface mapping, and the 
> 'ojbConcreteClass' property to have the appropriate concrete class 
> instantiated.

Yes, that should work. You define all common fields in the interface 
including ojbConcreteClass using getter/setter methods, and you need the 
PersistentFieldIntrospectorImpl or PersistentFieldAutoProxyImpl for the 
field access (OJB.properties) as there are no fields only bean methods.
You also should not need factory-class/factory-method now because OJB 
shouldn't try to instantiate the interface if ojbConcreteClass does not 
refer to it.

Tom


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How do you map a reference to an interface-backed class? (non-trivial)

[Andrew Clute <an...@osn.state.oh.us>]

I have looked at all of the examples, I can't seem to make heads or 
tails of how to handle my situation. I want to map a class that has a 
reference to an object, that can one of many different objects, that 
all implement the same interface.

Example

Interface A{

}

class B implements A
{}

class C implements A
{}

class Z
{
	private A myA;
}

So, in this case, how do I map class Z since it's member variable is of 
Type A, but I want the concrete object, either of Type B or C to be 
filled in.

Seems like there is no known strategy to do this: "Using Interfaces 
With OJB" talks about a similar situation, but assumes that there is 
only one concrete class that can be instantiated for the reference (the 
factory-method assumes that it will only return one concrete class 
type).

Seems like I need a combination of the Interface mapping, and the 
'ojbConcreteClass' property to have the appropriate concrete class 
instantiated.

Thoughts? What am I missing?

-Andrew


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