bind from a class name

[Bill de hOra]

Is there a way to bind from a class name (ie the class' string name)
instead of a .class?

Bill

[Bob Lee]

Can you give an example of what you're looking for?

Thanks,

Bob

[Dhanji R. Prasanna]

Can't you use Class.forName in between?

On Thu, Mar 25, 2010 at 1:04 PM, Bill de hOra <bi...@dehora.net> wrote:

Is there a way to bind from a class name (ie the class' string name) instead of a .class?

Bill

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[Bill de hOra]

It's to be able to wire in an implementation from a simple plugin
descriptor, ie from a text/xml file rather than code.

I tried Dhanji's idea - Class.forName returns Class<?>, which can be
cast to the interface, eg,

try {
Class<?> aClass =
Class.forName("presence.service.MemoryPresenceService");
PresenceService o = (PresenceService)aClass.newInstance();
bind(PresenceService.class).to(o.getClass());
} catch (Exception e) {
....
}

the downside isn't so much a cast as having to have '(PresenceService)'
in the code itself.

I suppose I could go OSGi, but that's a big meal to eat. I'm wondering
if scanning for module classes annotated with @Plugin or something
wouldn't be better, ie ask plugin providers to ship a guice module
instead of using text config.

Bill

[Dan Godfrey]

If you're on Java6 and can put the text file on the classpath, you
could have the ServiceLoader instead of annotating and then scanning
for @Plugin.

http://java.sun.com/javase/6/docs/api/java/util/ServiceLoader.html

[Yegor]

>    PresenceService o = (PresenceService)aClass.newInstance();
>    bind(PresenceService.class).to(o.getClass());

Variable o seems unnecessary, as it is only used to get the class of
MemoryPresenceService, which you already have in variable aClass.
Instantiating the class unnecessarily may lead to bugs/performance
issues. I recommend doing this instead:

try {
  Class<PresenceService> aClass = (Class<PresenceService>)
Class.forName("presence.service.MemoryPresenceService");
  bind(PresenceService.class).to(aClass);
} catch (Exception e) {
....
}