Vladimir Egorov wrote:
Hi Ant Users,
I would like to change the value of a task attribute on the fly, without
editing Ant xml file, by setting a runtime system property like this:
junit.showoutput=true --> get junit to show test output by default
java.fork=true --> fork by default
etc.
While this can be implemented for an individual task, I believe that it
should be done in core Ant, so that it works for all tasks without extra
work for task developers.
Do Ant Users feel this would be useful to have in core Ant? Has anyone
asked for this? Is there an extension mechanism in Ant that can be used
to do this? Is there a property-to-xml convention that would take care
of the nested elements?
Occasionally there are some 'magic' switches to change behaviour of
javac, but otherwise they are left alone
Now -gratuitous product placement time- our little SmartFrog deployment
framework does let you do late binding of existing attributes, because
all you are building up is a template on a template on a template,
presetdef taken to the n-th degree,
So I have a template for an Xmpp component
XmppComponent extends Prim {
xmppSchema extends XmppSchema;
serviceName LAZY server;
port 5222;
requireEncryption true;
resource "SmartFrog";
presence false;
useTLS false;
}
which I can extend to one with a classname (as the name of the
implementing class is just another attribute)
XmppClient extends XmppComponent {
sfClass "org.smartfrog.services.xmpp.XmppClientImpl";
}
and then define one for google:
GoogleChatClient extends XmppClient {
server "talk.google.com";
serviceName "gmail.com";
}
This is still abstract, it needs a user and password.
In any deployment descriptor I can do something called 'placement',
where I patch in a new value to the base system. So, to turn on useTLS
everywhere, I go
XmppComponent:useTLS true;
This is very powerful, but at the same time, very dangerous. Why?
Because now the state of your system depends on the order of the files
you read in, and all their values. It is still declarative, but a lot
harder to work out what the declarations will be, as any placement can
change the behaviour of any other template.
So
1. I see the value in the idea -we use it at work
2. I also think its very dangerous
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