Dispose
Let's start on defining an object type that requires dependency injection and that a callback has to be invoked once application will be shutdown:
import org.nnsoft.guice.lifegycle.Dispose; @Singleton // not necessary, but let's add some spice public class MyServiceImpl { @Inject private Dependency dependency; // setter omitted for simplicity @Dispose public void tearDown() { ... } }
All users have to do, is adding the DisposeModule when creating the Injector:
import static com.google.inject.Guice.createInjector; import org.nnsoft.guice.lifegycle.DisposeModule; ... Injector injector = createInjector( new DisposeModule(), ... );
Then, require the org.nnsoft.guice.lifegycle.Disposer injection to shutdown the application:
import org.nnsoft.guice.lifegycle.Disposer; ... Runtime.getRuntime().addShutdownHook( new Thread() { public void run() { injector.getInstance( Disposer.class ).dispose(); } } );
Of course, same concept can be applied to any listener javax.servlet.ServletContextListener:
import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; public final class ContextListener implements ServletContextListener { private Injector injector; public void contextDestroyed( ServletContextEvent event ) { injector.getInstance( Disposer.class ).dispose(); } public void contextInitialized( ServletContextEvent event ) { ... } }
Dispose Handling
Users interested on tracking/logging/... objects dispose progresses, can register a org.nnsoft.guice.lifegycle.DisposeHandler, which has the following methods signatures:
public interface DisposeHandler { <I> void onSuccess( I injectee ); <I, E extends Throwable> void onError( I injectee, E error ); }
A DisposeHandler instance can be passed to Disposer#dispose() method:
injector.getInstance( Disposer.class ).dispose( new DisposeHandler { public <I> void onSuccess( I injectee ) { logger.info( "Object {} successfully released resources", injectee ); } public <I, E extends Throwable> void onError( I injectee, E error ) { logger.error( "Impossible to released resources of " + injectee, error ); } } );
Customization
The DisposeModule module supports dynamic definition of the annotation has to be handled; let's replace the org.nnsoft.guice.lifegycle.Dispose with the javax.annotation.PreDestroy:
import javax.annotation.PreDestroy; @Singleton // not necessary, but let's add some spice public class MyServiceImpl { @Inject private Dependency dependency; // setter omitted for simplicity @PreDestroy public void tearDown() { ... } }
then, create the Injector:
import static com.google.inject.Guice.createInjector; import javax.annotation.PreDestroy; import org.nnsoft.guice.lifegycle.AfterInjectionModule; ... Injector injector = createInjector( new DisposeModule( PreDestroy.class, Matchers.any() ), ... );