JAXB - The JAXB Context

Posted 2020-07-08 huey

As we have seen, an object of the class JAXBContext must be constructed as a starting point for other operations. One way is to create a context from a colon separated list of packages.

JAXBContext ctxt = JAXBContext.newInstance( "some foo:more.bar" );

Each package must contain its own class ObjectFactory or a file named jaxb.index. An ObjectFactory class is generated by the XML schema compiler, and therefore this form of newInstance is usually used in connection with schema derived classes. For JAXB annotated Java code, you may use the package path form as well, either with a hand-written ObjectFactory class or with a jaxb.index resource file containing a list of the class names to be considered by JAXB. This file simply lists the class names relative to the package where it occurs, e.g.:

# package some.foo
# class some.foo.Foo
Foo
# inner class some.foo.Foo.Boo
Foo.Boo

An alternative form of the newInstance method lists all classes that the new context should recognize.

JAXBContext ctxt = JAXBContext.newInstance( Foo.class, Bar.class );

Usually, the top level classes are sufficient since JAXB will follow, recursively, all static references, such as the types of instance variables. Subclasses, however, are not included.

If packages or classes are associated with namespaces, the packages or classes associated with a JAXB context also determine the namespace declarations written as attributes into the top-level element of the generated XML document.