On Friday, March 14, 2003, at 06:31 AM, Joe Fialli wrote:
> Han Ming Ong wrote:
>
>> Guys,
>>
>> Given the following schema snippets:
>>
>> <xs:element name="app">
>> <xs:complexType>
>> <xs:sequence>
>> <xs:element ref="comment-before-root" minOccurs="0"
>> maxOccurs="unbounded"/>
>> <xs:element ref="desc" maxOccurs="unbounded" />
>> </xs:sequence>
>> </xs:complexType>
>> </xs:element>
>>
>> <xs:element name="desc">
>> <xs:complexType>
>> <xs:sequence>
>> ...
>> </xs:sequence>
>> </xs:complexType>
>> </xs:element>
>>
>> I get the following API for returning desc in the interface AppType:
>>
>> DescType[] getDesc();
>>
>> Of course the interface DescType inherits from interface Desc. I
>> don't care about the rationale behind *not* returning Desc[] in the RI
>
> The rationale for the method signature returning the type of the
> element is very important
> for the general case. Future support for type substitution requires
> this
> return type.
>
> Example:
>
> Given following XML Schema:
>
> <complexType name="Base"> ....
> <complexType name="Derived"> <!-- derives by extension from Base -->
> <element name="anElement" type="Base"/>
>
> Any property referencing AnElement is bound to the following methods:
> Base getAnElement()
> void setAnElement(Base value)
>
> Here are the Java interfaces for above.
>
> public interface Base ....
> public interface Derived implements Base ..
> public interface AnElement extends Base, javax.xml.bind.Element ...
>
> It is important that one can handle instances of both Base and Derived
> for the JAXB property, AnElement. Following are legal instances
> of anElement in an xml document.
>
> <anElement xsi:type="Derived"> ..Content model for Base and
> Derived..</anElement>.
> <anElement>...Content model for Base ... </anElement>
>
> If the signature was constrained to the element interface, one would
> not
> be able
> to return an instance of Derived since it is not an instance of
> AnElement.
>
Why doesn't JAXB always return as an instance of AnElement, regardless
of the actual type indicated in the XML doc?
A lot of times, I'm just concerned that it is an an instance of
AnElement. If I want to find out the actual type (for whatever reason),
give me an method to do it (it maybe already there, I didn't look at
the API docs).
> It is true that your case with anonymous complex type definition that
> does not derive
> from anything does not allow for type substitution. However, there is a
> wish to not generate different looking JAXB Java properties to reflect
> the
> underlying XML as often as possible.
>
>>
>> but I would like to know if there is a way I could customize it in
>> JAXB
>> generation?
>
> The current implementation is not capable of customizing the value
> returned
> by a JAXB property.
>
> In the interest of evaluating the capability that you need and
> what granularity it should be at, could you provide the rationale for
> why you need this capability.
Reduction in complexity. Always good.
Thanks for listening.
>
> It would be possible to consider returning an instance of Desc for your
> example;
> however, it probably would be preferable for the signature to remain
> as is.
> Otherwise, it would introduce a JAXB customization that would allow
> the customizer to easily restrict the XML instance documents that the
> JAXB method
> signatures could handle.
>
> -Joe Fialli, Sun Microsystems
>
>>
>>
>> Naively changing the codes manually on my part result in
>> java.lang.ArrayStoreException eventually.
>>
>> Thanks much, Han Ming