core/src/com/google/inject/internal/Initializer.java
<T> Initializable<T> requestInjection(
      InjectorImpl injector,
      T instance,
      Binding<T> binding,
      Object source,
      Set<InjectionPoint> injectionPoints) {
    checkNotNull(source);
    Preconditions.checkState(
        !validationStarted, "Member injection could not be requested after validation is started");
    ProvisionListenerStackCallback<T> provisionCallback =
        binding == null ? null : injector.provisionListenerStore.get(binding);

    // short circuit if the object has no injections or listeners.
    if (instance == null
        || (injectionPoints.isEmpty()
            && !injector.membersInjectorStore.hasTypeListeners()
            && provisionCallback == null)) {
      return Initializables.of(instance);
    }

    if (initializablesCache.containsKey(instance)) {
      @SuppressWarnings("unchecked") // Map from T to InjectableReference<T>
      Initializable<T> cached = (Initializable<T>) initializablesCache.get(instance);
      return cached;
    }

    InjectableReference<T> injectableReference =
        new InjectableReference<T>(
            injector,
            instance,
            binding == null ? null : binding.getKey(),
            provisionCallback,
            source,
            cycleDetectingLockFactory.create(instance.getClass()));
    initializablesCache.put(instance, injectableReference);
    pendingInjections.add(injectableReference);
    return injectableReference;
  }
<T> Initializable<T> requestInjection(
      InjectorImpl injector,
      T instance,
      Binding<T> binding,
      Object source,
      Set<InjectionPoint> injectionPoints) {
    checkNotNull(source);
    Preconditions.checkState(
        !validationStarted, "Member injection could not be requested after validation is started");
    ProvisionListenerStackCallback<T> provisionCallback =
        binding == null ? null : injector.provisionListenerStore.get(binding);

    // short circuit if the object has no injections or listeners.
    if (instance == null
        || (injectionPoints.isEmpty()
            && !injector.membersInjectorStore.hasTypeListeners()
            && provisionCallback == null)) {
      return Initializables.of(instance);
    }

    if (initializablesCache.containsKey(instance)) {
      @SuppressWarnings("unchecked") // Map from T to InjectableReference<T>
      Initializable<T> cached = (Initializable<T>) initializablesCache.get(instance);
      return cached;
    }

    InjectableReference<T> injectableReference =
        new InjectableReference<T>(
            injector,
            instance,
            binding == null ? null : binding.getKey(),
            provisionCallback,
            source,
            cycleDetectingLockFactory.create(instance.getClass()));
    initializablesCache.put(instance, injectableReference);
    pendingInjections.add(injectableReference);
    return injectableReference;
  }
Registers an instance for member injection when that step is performed.

@param instance an instance that optionally has members to be injected (each annotated
with @Inject).
@param binding the binding that caused this initializable to be created, if it exists.
@param source the source location that this injection was requested