Is it possible to generate a XSD from a JAXB-annotated class?

Yes, you can use the generateSchema method on JAXBContext:

JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
SchemaOutputResolver sor = new MySchemaOutputResolver();
jaxbContext.generateSchema(sor);

You leverage an implementation of SchemaOutputResolver to control where the output goes:

public class MySchemaOutputResolver extends SchemaOutputResolver {

    public Result createOutput(String namespaceURI, String suggestedFileName) throws IOException {
        File file = new File(suggestedFileName);
        StreamResult result = new StreamResult(file);
        result.setSystemId(file.toURI().toURL().toString());
        return result;
    }

}