Can I inject objects in regular classes in GWT using GIN?

For instance, I have the GIN module which includes the binding for class A. While in class B (B is not bind using GIN), can I just simply use:

@Inject private A a;

to inject class A? I tried in my project, and looks like I got null pointer for object a. No idea why.

Because you need to instantiate your B class with GIN also.

For example with @UiFields you can use (provided true) and then inject them in the constructor, like this:

    /*Class B is not binded by GIN*/
    public class B {
        @Inject
        C cInstance; //C is binded by GIN
    }

/*Class A is binded with GIN*/
    public class A extends ViewImpl{

                @UiField(provided=true)
                B myWidget;

                //and then

                @Inject
                public A (UiBinder binder, B myWidget){
                   this.myWidget = myWidget;  //cInstance inside of it is injected!
                }
        }

After this kind of injection of B, all the @Inject annotations inside of B should resolve as expected.

And in case you instantiate A with GWT.create / new keyword - myWidget reference for B instance will be null also