wow, thanks so much, this is perfect. Really appreciate the help.
On Aug 11, 4:52 pm, Jean-Francois Poilpret <[email protected]>
wrote:
> Jeremy Chone wrote:
> > Hi,
>
> > I would like intercept all object created by Guice to check if they
> > have init()/shutdown() methods. What is the best way to do that. I am
> > getting a little confused with InjectionListener, TypeListener, ...
>
> Hi Jeremy,
>
> you have to write a TypeListener/InjectionListener combination and bind
> them in one Module, with a Matcher implementation that retains only
> classes that have init/shutdown methods:
>
> public class LifecycleTypeListener implements TypeListener
> {
> public LifecycleTypeListener(InjectionListener<Object>
> injectionListener)
> {
> _injectionListener = injectionListener;
> }
>
> public <I> void hear(TypeLiteral<I> type, TypeEncounter<I> encounter)
> {
> encounter.register(_injectionListener);
> }
>
> final private InjectionListener<Object> _injectionListener;
>
> }
>
> public class LifecycleInjectionListener implements InjectionListener<Object>
> {
> public void afterInjection(Object injectee)
> {
> // injectee has init / shutdown methods, you can call them by
> reflection
> // put your processing here
> }
>
> }
>
> public final class Matchers
> {
> static final public Matcher<TypeLiteral<?>> classSupportsLifecycle()
> {
> return new AbstractMatcher<TypeLiteral<?>>()
> {
> public boolean matches(TypeLiteral<?> type)
> {
> boolean hasInit = false;
> boolean hasShutdown = false;
> for (Method m: type.getRawType().getMethods())
> {
> if ("init".equals(m.getName()))
> {
> hasInit = true;
> }
> else if ("shutdown".equals(m.getName()))
> {
> hasShutdown = true;
> }
> }
> return hasInit && hasShutdown;
> }
> };
> }
>
> }
>
> final public class LifecycleModule extends AbstractModule
> {
> @Override protected void configure()
> {
> LifecycleInjectionListener injectionListener = new
> LifecycleInjectionListener();
> requestInjection(injectionListener);
> LifecycleTypeListener typeListener = new
> LifecycleTypeListener(injectionListener);
> bindListener(Matchers.classSupportsLifecycle(), typeListener);
> }
>
> }
>
> That's mainly it for your case.
> In the example above I took it for granted that you required classes to
> have both init AND shutdown methods.
> If you want to process a class if it has EITHER of this method, you
> would create two different Matchers, 2 different TypeListeners and 2
> different InjectionListener, and you would bind both TypeListeners.
> Note that the Matcher I put in the example is not very safe in that it
> doesn't check whether init/shutdown methods take the right arguments,
> this should be further adapted to make sure that only the correct
> init()/shutdown() methods are retained.
>
> Note that the situation would be easier if you defined interfaces for
> init/shutdown methods and check only for classes that implement these
> interfaces, in this case you could improve the InjectionListener as follows:
>
> public class LifecycleInjectionListener implements InjectionListener<?
> extends Lifecycle>
> {
> public void afterInjection(Lifecycle injectee)
> {
> }
>
> }
>
> And of course, the Matcher would be simpler as well.
>
> Hope this helps
>
> Jean-Francois
>
>
>
> > Jeremy,
> > --
> > Jeremy Chone
> > +1 415 699 9912
> >www.jeremychone.com<http://www.jeremychone.com>
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