Catalog is infact passed and used by XJC while parsing the schema for building the model.
These warnings are because of an issue in XJC where it uses catalog to resolve imported schemas while
building the forest, but during schema correctness check it does not set the
entity resolver. In com.sun.tools.xjc.api.impl.s2j.SchemaCompilerImpl.java#230,
EntityResolver is not set on the SchemaFactory. This results in to unnecessary
warning thrown during schema resolution.
Filed issue on jaxb:https://jaxb.dev.java.net/issues/show_bug.cgi?id=795
Workaround: One could set com.sun.tools.xjc.api.impl.s2j.SchemaCompilerImpl.noCorrectnessCheck=true so that XJC does not do schema correctness check.