Java 类com.google.common.util.concurrent.ForwardingListenableFuture 实例源码

public <T> ListenableFuture<T> scopeCallbacks(final ListenableFuture<T> callback) {
    final ScopedObjects scope = getScope();
    return new ForwardingListenableFuture<T>() {
        @Override
        protected ListenableFuture<T> delegate() {
            return callback;
        }

        @Override
        public void addListener(Runnable listener, Executor exec) {
            super.addListener(listener, scope(exec, scope));
        }
    };
}

private <T> ListenableFuture<T> wrapListenableFuture(final ListenableFuture<T> delegate) {
    /*
     * This creates a forwarding Future that overrides calls to get(...) to check, via the
     * ThreadLocal, if the caller is doing a blocking call on a thread from this executor. If
     * so, we detect this as a deadlock and throw an ExecutionException even though it may not
     * be a deadlock if there are more than 1 thread in the pool. Either way, there's bad
     * practice somewhere, either on the client side for doing a blocking call or in the
     * framework's threading model.
     */
    return new ForwardingListenableFuture.SimpleForwardingListenableFuture<T>(delegate) {
        @Override
        public T get() throws InterruptedException, ExecutionException {
            checkDeadLockDetectorTL();
            return super.get();
        }

        @Override
        public T get(final long timeout, @Nonnull final TimeUnit unit)
                throws InterruptedException, ExecutionException, TimeoutException {
            checkDeadLockDetectorTL();
            return super.get(timeout, unit);
        }

        void checkDeadLockDetectorTL() throws ExecutionException {
            if (deadlockDetector.get().isSet()) {
                throw new ExecutionException("A potential deadlock was detected.",
                        deadlockExceptionFunction.get());
            }
        }
    };
}