How to retrieve the value of a "fixed" attribute

[epbernard]

JPA 2 has added a new attribute to the persistence-unit element. It is required but is fixed at the same time so the user doesn't have to set it explicitly.

I can't seem to find a way to let JBoss XB to populate my mapped attribute with he fixed value. I always end up with null. How can I do that?

PS: I can't hard code the value as the binding model is supposed to bind both JPA1 and JPA2 so null != 2.0

Here is the attribute declaration

<xsd:attribute name="version" type="persistence:versionType"
 fixed="2.0" use="required"/>

[dmlloyd]

So the default value of the field depends on the JPA spec in force? How is that differentiated? Through the namespace?

[aloubyansky]

Use controls presence. If use="required" the attribute must appear in the XML.
Fixed is a value constraint. If the attribute is present and different from the fixed value the parsing will fail.

All this stuff is handled by the underlying xml parser, which is xerces SAX in our case. Xerces will include fixed and default attributes into org.xml.sax.Attributes only if schema validation is enabled.

In XB you can do that by unmarshaller.setSchemaValidation(true);

[epbernard]

So the default value of the field depends on the JPA spec in force? How is that differentiated? Through the namespace?

Different version of the xsd, there is also a version attribute on the schema (unrelated though in theory)

[dmlloyd]

I guess Alexey nailed it. Anyway it's unlikely we'd ever turn on validation due to perf. reasons.

My analysis of handing this kind of situation (two very similar but not identical namespaces with JBossXB or JAXB in general) came to the conclusion that you can't really do it cleanly without having completely separate object models, which of course is a ton of redundancy. Maybe there's some way you can hack it into telling you what namespace was parsed? Setting it as a property on your root element or something?

[aloubyansky]

We could create an annotation for this.

[epbernard]

Use controls presence. If use="required" the attribute must appear in the XML.
Fixed is a value constraint. If the attribute is present and different from the fixed value the parsing will fail.

You sure? My schema parsing is failing when I add unexpected elements (blah) but they pass if I don't set version.
Even worse, if I set version, then it fails

Caused by: org.xml.sax.SAXException: cvc-complex-type.3.2.2: Attribute 'version' is not allowed to appear in element 'persistence-unit'

All this stuff is handled by the underlying xml parser, which is xerces SAX in our case. Xerces will include fixed and default attributes into org.xml.sax.Attributes only if schema validation is enabled.

In XB you can do that by unmarshaller.setSchemaValidation(true);

It's for JBoss Metadata's JPA parsing. Do you know the piece of code that set the unmarshaller?

[aloubyansky]

Yes, I am sure. I have tested it.

The unmarshaller is initialized (depends on how you write your tests, of course, but for many...) in JBossXBTestDelegate which is in tests of metadata/common.

[aloubyansky]

PS: XB also does some limited validation especially for elements in a sequence. It's not a feature in itself but a side effect of the implementation. So, maybe it was the XB error.

[epbernard]

The unmarshaller is initialized (depends on how you write your tests, of course, but for many...) in JBossXBTestDelegate which is in tests of metadata/common.

I mean how do I make sure my PersistenceMetadata and PersistenceUnitMetadata are parsed with validation enabled in the grand scheme of JBoss AS. Having passing unit tests while the core product fails will do me no good :)

[aloubyansky]

Each parsing deployer (that extends https://anonsvn.jboss.org/repos/jbossas/projects/jboss-deployers/trunk/deployers-vfs-spi/src/main/java/org/jboss/deployers/vfs/spi/deployer/JBossXBDeployer.java) has property useSchemaValidation.
You can actually see it (set to false or commented out ;) ) in ejb-deployer-jboss-beans.xml and ear-deployer-jboss-beans.xml

[epbernard]

Seems I am out of luck.
PersistenceUnitDeployer extends AbstractSimpleRealDeployer extends AbstractRealDeployer extends AbstractDeployer

So my chain does not seem to extend JBossXBDeployer.java

[emuckenhuber]

As far as i can remember there is a PersistenceParsingDeployer extending JBossXBDeployer, doing the actual parsing of the persistence.xml.

[aloubyansky]

Yes

<bean name="PersistenceParsingDeployer" class="org.jboss.jpa.deployers.PersistenceParsingDeployer"/>