Hi Craig,
+1
Regards Michael
Another vote on this proposal. I've added the ability to specify
multiple comma-delimited types to element-type, key-type, value-type,
and field-type but specified that this is not portable.
Issue 139:
This would allow more specific field type to be specified at deployment
time compared to compile time. For example, a field of type Object could
be specified in the jdo metadata as containing only instances of type
SimpleClass.
<proposal>
18.14 ELEMENT field
<!ATTLIST field field-type CDATA #IMPLIED>
The field-type attribute is used to specify a more restrictive type than
the field definition in the class. This might be required in order to
map the field to the datastore. To be portable, specify the name of a
single type that is itself able to be mapped to the datastore (e.g. a
field of type Object can specify field-type=”Integer”). To specify
multiple types that the field might contain, use a comma-separated list
of types, although this cannot be portably mapped.
18.14.1ELEMENT collection
element-type
The element-type attribute specifies the type of the elements. The type
name uses Java language rules for naming: if no package is included in
the name, the package name is assumed to be the same package as the
persistence-capable class. Inner classes are identified by the "$"
marker. Classes Boolean, Byte, Character, Double, Float, Integer, Long,
Number, Object, Short, String, and StringBuffer are treated exactly as
in the Java language: they are first checked to see if they are in the
package in which they are used, and if not, assumed to be in the
java.lang package. To be portable, specify the name of a single type
that is itself able to be mapped to the datastore (e.g. a field of type
Object can specify field-type=”Integer”). To specify multiple types that
the field might contain, use a comma-separated list of types, although
this cannot be portably mapped.
18.14.2 ELEMENT map
The key-type and value-type attributes specify the types of the key and
value, respectively. They follow the same rules as element-type in
element collection.
18.14.3 ELEMENT array
The element-type attribute is used to specify a more restrictive type
than the field definition in the class. This might be required in order
to map the field to the datastore. It follows the same rules as
element-type in element collection.
</proposal>
Craig
On Dec 28, 2005, at 1:33 PM, Michael Bouschen wrote:
Hi Craig,
Hi Andy,
I don't have a problem with using the element-type to be a
comma-separated list as a vendor extension, but in general there is
no way to map a heterogeneous (Object or interface type) field.
does this apply the metadata attributes field-type, element-type,
key-type and value-type?
So I don't think that we should specify the comma-separated list of
possible types as a standard technique.
What do others think about this?
I think support for a field with multiple types in its field-type
attribute should not be required. But maybe it makes sense to specify
the syntax as a comma separated list of type names in case a JDO
implementation does support this feature.
Regards Michael
Craig
On Dec 21, 2005, at 12:11 AM, Andy Jefferson wrote:
Hi Craig,
This proposal would allow more specific field type to be specified at
deployment time compared to compile time. For example, a field of
type Object could be specified in the jdo metadata as containing only
instances of type SimpleClass.
I don't read the proposal as saying that the user should specify the
type(s) as comma-separated if they want a field declared as Object
to store class A or class B or class C. What does the user do when
they have a field declared as Object and want to do this ?
--
Andy
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!
--
Michael Bouschen [EMAIL PROTECTED] Engineering GmbH
mailto:[EMAIL PROTECTED] http://www.tech.spree.de/
Tel.:++49/30/235 520-33 Buelowstr. 66
Fax.:++49/30/2175 2012 D-10783 Berlin
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!
--
Michael Bouschen [EMAIL PROTECTED] Engineering GmbH
mailto:[EMAIL PROTECTED] http://www.tech.spree.de/
Tel.:++49/30/235 520-33 Buelowstr. 66
Fax.:++49/30/2175 2012 D-10783 Berlin
