I use the isSet functionality to achieve this. I place the following at the
top of my XSD:
<xsd:annotation>
<xsd:appinfo>
<jxb:globalBindings generateIsSetMethod="true"/>
</xsd:appinfo>
</xsd:annotation>
If I have an element X then JAXB will generate an isSetX method that returns
a boolean determining whether the element/attribute was explicitly set or
not.
There is a distinction between whether an element/attribute has been set and
whether or not it is null. Depending upon your data/application it may be
equivalent for you to regard a null object as an element/attribute that has
not been set, but it is possible to explicitly set an element/attribute to
null so you need to be careful to make this distinction if your application
needs it.
I've probably not made that very clear, so let me give an example! If I
have two xsd:string elements A and B without any defaults and I create the
object via ObjectFactory, then getA(), getB(), isSetA(), and isSetB() will
return null, null, false, and false respectively. (No surprises there).
However, if I then call setA(null), then getA(), getB(), isSetA(), and
isSetB() will return null, null, true, and false respectively - not
particularly surprising when you think about it, but can catch you out if
you're not careful!
Hope that helps and makes sense to someone!
Marcus
-----Original Message-----
From: Jon Richards [mailto:jonrichards_at_onetel.net.uk]
Sent: Wednesday, December 10, 2003 7:36 AM
To: users_at_jaxb.dev.java.net
Subject: accessing _has elements
Appologies if this is not the correct forum for this question.
I have generated classes for a schema where some elements are
minoccurs="0".
After unmarshalling I would like to know whether the element
was present or not. Objects are fine as they return null, but
base types like int will return 0.
Unfortunately the 'has' attributes in the impl classes are
protected, and the type interface does not provide access
methods for these attributes.
Is there a way of finding out whether elements were present
or not? If not is it appropriate for the next JAXB release to
add access methods for the 'has' methods?
Regards,
Jon Richards.