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package net.peierls.util; import java.util.concurrent.TimeUnit; import com.google.inject.AbstractModule; import com.google.inject.Guice; import com.google.inject.Inject; import com.google.inject.Injector; import com.google.inject.Provider; /** * An artificial example of using ConcurrentSingletonScope. */ public class ConcurrentSingletonExample { public static void main(String... args) throws InterruptedException { long start = System.nanoTime(); Injector injector = Guice.createInjector( new AbstractModule() { public void configure() { bind(A.class); bind(B.class); bind(C.class); ConcurrentSingletonScope.install(binder()); } } ); A a = injector.getInstance(A.class); long elapsed = System.nanoTime() - start; System.out.printf("Completed in %d seconds%n", TimeUnit.NANOSECONDS.toSeconds(elapsed)); } // Concurrently provided "services" A, B, and C. A depends on B and C. @ConcurrentSingleton static class A { @Inject public A(Provider<B> b, Provider<C> c) { try { System.out.printf("Starting A on thread %s%n", Thread.currentThread().getName()); TimeUnit.SECONDS.sleep(1); System.out.printf("A getting B and C instances on thread %s%n", Thread.currentThread().getName()); b.get(); c.get(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { System.out.println("Started A"); } } } @ConcurrentSingleton static class B { @Inject public B() { try { System.out.printf("Starting B on thread %s%n", Thread.currentThread().getName()); TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { System.out.println("Started B"); } } } @ConcurrentSingleton static class C { @Inject public C() { try { System.out.printf("Starting C on thread %s%n", Thread.currentThread().getName()); TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { System.out.println("Started C"); } } } }

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