OK. Maybe I didn't explain it understandable.
I want a parameter to tell Seam not to overwrite existing fields. If I've a field in my component, which is not null and Seam doesn't find a value in its context for this field, I don't want Seam to overwrite my field with null. Seam should do nothing.
Don't use injection. Use an ordinary lookup Contexts.getXXXContext().get("name") or Component.getInstance("name", true).