This is constructor ordering issue. When constructing an object in Java, at
first the superclass constructor is executed and the object's own
constructor. Since the ComponentInstantionListener is executed by the *
superclass* of your Page, which will call your init method (annotated by
@Inject), the constructor and field initialization of Page itself isn't
executed yet. That's why the Label message is still null.
Lars
On Mon, May 5, 2008 at 1:02 PM, Ståle Undheim <[EMAIL PROTECTED]> wrote:
> I have just started using Wicket, and I use Guice for bindings.
> However, I got into a situation where private final fields initialized
> directly would be null.
>
> Here is the code in my WebApplication constructor:
>
> addComponentInstantiationListener(new IComponentInstantiationListener() {
> private final Injector injector = Guice.createInjector(new
> Module());
>
> public void onInstantiation(Component component) {
> injector.injectMembers(component);
> }
> });
>
> I prefered this to the wicket guice plugin, that seems to do the above
> steps manually by reimplementing Guice logic.
>
> Here is my simple Page body:
>
> private final Label message = new Label("message", "Text");
>
> private Service service;
>
> @Inject
> public void init(Service service) {
> this.service = service;
> add(message);
> }
>
> I get a NullPointerException on the add, because message is null.
> According to my understanding of Java, I can`t even see how this is
> possible. The default constructor should be called regardless, and
> thus message would get set.
>
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