JAXB and Boolean

It turns out that by default, JAXB 2.2, the level in Java 7, generates the wrong kinds of getters for Boolean (wrapper object) fields. It generates isXXX() getters instead of getXXX() getters. And according to the JavaBeans spec, only boolean primitives are supposed to do that.

See https://java.net/jira/browse/JAXB-131

Among other things, Apache Commons BeanUtils copyProperties() follows the spec and thus doesn’t copy Booleans.

The fix is to use a JAXB compiler option, -enableIntrospection. See https://jaxb.java.net/nonav/2.2.1/docs/xjc.html

In the JAX-WS <wsimport> Ant task, it looks like this:

        <target name="wsimport">
            <wsimport sourcedestdir="${gen.src}" target="2.2"
                <xjcarg value="-enableIntrospection"/>

This causes getXXX() methods to be generated instead of isXXX() methods. (I found myself thinking it would be nice if both styles of getters were produced, but I admit I don’t know if that would violate some other specification or convention.)

xs:boolean with minOccurs=”0”

Related is the fact that, with this version of JAXB, XML schema types that have minOccurs=0 get generated as “wrapper” classes (e.g. Boolean) instead of primitives (boolean). This is so that the value can be null if the XML element is missing or empty.

Based on some non-null-safe legacy code that I’m migrating, it seems that earlier versions of JAXB behaved differently, at least under WebSphere 6.1: either using primitives or otherwise returning a default value on empty.

Bonus topic

A different issue we saw with JAX-WS/JAXB under WAS 8.5.5/Java7, was that xs:string values with xsi:nil="true", were sometimes returning null rather than empty string. (Specifically, on the second and subsequent unmarshals. See forum thread.)

WebSphere 8.5.5 has an optimization option, com.ibm.xml.xlxp.jaxb.opti.level, whose default value exhibits this behavior, but which can be set to a “disabled” value that reverts to the earlier behavior.