XML & JAXB: pass attribute into value

Question

I have a large amount of objects generated through JAXB (maven-jaxb2-plugin) and annotate them with the jaxb2-annotate-plugin. These classes may define a RelationType and I'd like to annotate them with the corresponding @RelationType annotation. I use an XPath expression to find the name attribute in the XSD and annotate the class, passing its specific type into the annotation. An example of this is the following:

<jaxb:bindings node="//xsd:complexType[@name='SomeRelationType']">
    <annox:annotate target="class">@com.example.RelationType(type = "SomeRelationType")</annox:annotate>
</jaxb:bindings>

which maps on the following XSD snippet:

<xsd:complexType name="SomeRelationType">
    <xsd:complexContent>
        <xsd:extension base="RelationType">
            <xsd:sequence>
                <xsd:element name="someValue" type="SomeValue"/>
                <xsd:element name="otherValue" type="OtherValue"/>                     
            </xsd:sequence>
        </xsd:extension>
    </xsd:complexContent>
</xsd:complexType>

I find the ComplexType with the SomeRelationType name and annotate the class with a @RelationType annotation, which has the SomeRelationType as its type parameter. It would generate the following class:

@RelationType(type = "SomeRelationType")
public class SomeRelationType extends RelationType implements Serializable {
    private final static long serialVersionUID = 1L;
    protected SomeValue someValue;
    protected OtherValue otherValue;    
}

This works fine if it were just a few domain objects. But I have a large amount and defining every annotation manually is not only tedious but also bad in terms of change and expansion.

To generify it, I can rewrite the XPath expression to the following:

<jaxb:bindings node="//xsd:complexType[substring(@name, string-length(@name) - string-length('RelationType') + 1)]" multiple="true">
    <annox:annotate target="class">@com.example.RelationType(type = "SomeRelationType")</annox:annotate>
</jaxb:bindings>

The problem: The type parameter of my annotation is still defined as "SomeRelationType". It would be great if I could use the same @name as defined in the XPath expression. Then all the classes whose name ends with "RelationType" also automatically gets its @RelationType annotation with the correct type parameter.

It doesn't work as simple as doing the following of course, but it shows what I'd like to achieve:

<jaxb:bindings node="//xsd:complexType[substring(@name, string-length(@name) - string-length('RelationType') + 1)]" multiple="true">
    <annox:annotate target="class">@com.example.RelationType(type = @name)</annox:annotate>
</jaxb:bindings>

Is such a thing even possible or is this impossible in XML/JAXB?

score 0 · Accepted Answer · answered Mar 19 '16 at 13:35

But I have a large amount and defining every annotation manually is not only tedious but also bad in terms of change and expansion.

For me, @com.example.RelationType(type = "SomeRelationType") looks like a trivial metainformation which could be derived via reflection without any annotations. So check if there's a way to do "convention over configuration" thing.

The jaxb2-annotate-plugin does not and will not support parameterization, it would be too narrow and too complex to implement. Disclaimer I'm the author of the jaxb2-annotate-plugin.

I see two options:

Pre-generate bindings in your build. XML Schema is XML so writing XSLT to produce bindings files should not be too complicated.
Write an own XJC plugin to add annotations as you want them.
Bribe me to add parameterization to the jaxb2-annotate-plugin.

Right, just two options.

XML & JAXB: pass attribute into value

1 Answers1