On Wed, 18 Nov 2009, Peter Duniho wrote:
Tom Anderson wrote:
[...]
Am i right in thinking that all of these will force loading of Foo?
I think so. But I haven't checked the spec to make sure.
Does anyone have any other idioms? How about any opinions on which
idiom is best, or at least most idiomatic?
I find the question ironic. :) The fact is, you've got some
clearly non-idiomatic scenario, where for some reason your code has
managed to become dependent on the initialization of a class that it
does not in fact refer to in the process of being dependent on it.
Given that violation of a very fundamental assumption one normally
could make in a Java program, asking for an idiomatic solution to
the violation seems sort of silly to me. Your code is already
broken; any work-around is destined to be non-idiomatic. :)
What's really happening is more like this:
class FooMangler implements Mangler {
static {
ManglerRegistry.register("foo", FooMangler.class);
}
}
class ManglingParser extends org.xml.sax.helpers.DefaultHandler {
public void startElement (String uri, String localName, String qName, Attributes attrs) throws SAXException {
String manglerName = attrs.getValue("mangler");
Mangler mangler = ManglerRegistry.lookup(manglerName);
mangler.mangle(qName, attrs);
}
}
The idea is that manglers can take care of registering themselves - as
long as they're loaded. This is an old and fairly well-known pattern
(at least, not wildly obscure - in terms of birds, about as common as
a kingfisher is in England), although i certainly wouldn't say it's a
good one, or even a non-dubious one. 'Broken' is a bit too strong,
although only a bit.
methods. I'd prefer creating an instance of ManglerRegistry,
to it in the ManglingParser. This requires more coding, obviously,
different registries. Also, it allows registering the same mangler