[rules-dev] Declared types - extension

[Michael Anstis]

Here's some detail from Sotty:-

   - It is indeed necessary to declare a legacy class if you want another to
   extend it.


   - The classFieldAccessor constructor requires both getter and setter to
   be present for each field, so there's indeed a bug. A field must be
   inherited if and only if it has both getter and setter (right now, only the
   getter is checked). I have put an additional condition in the
   PackageBuilder: this will allow to extend non-bean "legacy" classes.


   - Currently, when you redeclare a field, it is overridden. On a second
   and third thought, I do not "like" this behaviour, so I have changed the PB
   to prevent fields from being overridden :)


   - It is still possible to redeclare a field with the same name if the
   type is the same


   - Declared metadata is already inherited by extenders

Thanks for the insights Sotty.

Mike

On 13 July 2011 13:00, Michael Anstis <michael.anstis at gmail.com> wrote:

> Wolfgang, still no news as to the expected behaviour :(
>
> Sotty, I appreciate you are probably busy with other activities, however
> any your thoughts on the following would be most welcome:-
>
>    - For POJOs is a field only added to the declared type if it has a
>    getter and setter (something laune said he'd seen; email earlier in this
>    thread)?
>    - Are fact-level annotations inherited?
>    - Are field-level annotations inherited?
>    - Type erasure on subclasses, if type A declares "myVar : String" and
>    type B extends A and declaring "myVar : Integer", what should happen?
>
> For others interested, here's some answers already received:
>
>    - Can declarative types extend Java POJOs and other declared types?
>
> <sotty> yes
>
>    - For POJO's do I need to include an "empty" declaration? So "declare
>    java.util.ArrayList end" if I want to "declare MyList extends ArrayList" in
>    a java.util package?
>
> <sotty> no, it should be enough to import the fqn or use it in the
> "extends".
> *<manstis> note this is different to what is documented in the Drools
> Expert user-guide
> *
> Thanks,
>
> Mike
>
>
> On 12 July 2011 13:12, Michael Anstis <michael.anstis at gmail.com> wrote:
>
>> https://issues.jboss.org/browse/JBRULES-3133 created.
>>
>>
>> On 12 July 2011 13:08, Michael Anstis <michael.anstis at gmail.com> wrote:
>>
>>> There's also a quirk regarding the class resolution:-
>>>
>>> Given Person class:-
>>>
>>> package com.guvnor.domain;
>>>
>>> import java.math.BigDecimal;
>>>
>>> public class Person {
>>>
>>>     private BigDecimal salary;
>>>
>>>     public BigDecimal getSalary() {
>>>         return salary;
>>>     }
>>>
>>>     public void setSalary(BigDecimal salary) {
>>>         this.salary = salary;
>>>     }
>>>
>>> }
>>>
>>>
>>> The following compiles OK:-
>>>
>>> package com.sample
>>>
>>> import com.guvnor.domain.Person
>>>
>>> declare Person
>>> end
>>>
>>> However the following does not (without explicitly importing
>>> java.math.BigDecimal - which is a field type in Person):-
>>>
>>> package com.sample
>>>
>>> import com.guvnor.domain.Person
>>> import com.guvnor.domain.Address
>>>
>>> declare Person
>>> end
>>>
>>> declare Person2 extends Person
>>>     flange : String
>>> end
>>>
>>> Error being "Unknown DroolsError class
>>> org.drools.compiler.TypeDeclarationError: Unable to find class 'BigDecimal'
>>> ".
>>>
>>> With kind regards,
>>>
>>> Mike
>>>
>>>
>>> On 11 July 2011 08:41, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>>>
>>>> Subsection 5.7.7 discusses 'extends' and describes how it is done for
>>>> types declared in Java.
>>>>
>>>> One finesse is apparently not documented: Java types must be proper
>>>> JavaBeans; otherwise the construction of the accessors will fail. (Try, for
>>>> instance, a property with a getter but no matching setter.)
>>>>
>>>> HTH
>>>> -W
>>>>
>>>>
>>>> On 10 July 2011 22:29, Michael Anstis <michael.anstis at gmail.com> wrote:
>>>>
>>>>> What's the rules around declared types extending another (declared)
>>>>> type?
>>>>>
>>>>> I've been asked to provide for declared type extension in Guvnor (by
>>>>> Prakash) but the Expert user-guide doesn't say it exists at the engine
>>>>> level.
>>>>>
>>>>> I tried "declare MyType extends java.util.ArrayList" and received a
>>>>> parser\compiler error stating "java.util.ArrayList was not a declared type"
>>>>> (or words to that effect) so some form of extension appears possible.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Mike
>>>>>
>>>>> _______________________________________________
>>>>> rules-dev mailing list
>>>>> rules-dev at lists.jboss.org
>>>>> https://lists.jboss.org/mailman/listinfo/rules-dev
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> rules-dev mailing list
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>>>>
>>>>
>>>
>>
>
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