Cache Guice Injector with TestNG

CachedModuleFactory.java

/**
 * @author Andrei Varabyeu
 */
public abstract class CachedModuleFactory implements IModuleFactory {

    private static volatile Injector parentInjector;

    private static final Object LOCK = new Object();

    private Injector getParentInjector() {
        /* make sure we create injector only once */
        if (null == parentInjector) {

            /* locks this area from concurrent calls for ALL instances */
            synchronized (LOCK) {
                if (null == parentInjector) {
                    parentInjector = Guice.createInjector(createParentModule());
                }
            }
        }

        return parentInjector;
    }


    abstract protected Module createParentModule();

    abstract protected Module createTestModule(ITestContext context, Class<?> testClass);


    @Override
    final public Module createModule(ITestContext context, Class<?> testClass) {
        Module childModule = createTestModule(context, testClass);
        if (testClass.isAnnotationPresent(UseCachedInjector.class)) {
            context.addInjector(Collections.singletonList(childModule),
                    getParentInjector().createChildInjector(childModule));
        }
        return childModule;
    }
}

UseCachedInjector.java

/**
 * @author Andrei Varabyeu
 */
@Retention(RUNTIME)
@Target({ElementType.TYPE})
public @interface UseCachedInjector {
}