The SpringBeanProcessor was updated in
RESTEASY-511 / RESTEASY-679 to better support Spring 3.1 @Configuration classes. However, while Spring makes no requirements on the visibility of methods in these classes, the bean processor is only looking for public methods.
Please see line 399 of org.jboss.resteasy.plugins.spring.SpringBeanProcessor.java
The current implementation uses getBeanClass(factoryClassName).getMethods(). This should probably be something more sophisticated, maybe utilizing Spring's own code like org.springframework.util.ReflectionUtils#getAllDeclaredMethods.
The workaround is obviously to set all declared methods in @Configuration classes to be public.