There is little problem with JAXB.
Given:
For an initialization of the class members from XSD supplied defaults, you can use the default-value-plugin of XJC.
See the website of the plugin.
Note that the ant task definition as explained in that documentation did not work for me. As explained here, the class paths for XJC and the plugin have to be separated. Specifying the path to the plugin when calling it works for me: