GWT Deferred Binding and Dependency Injection

Question

Assuming I have something like so

Interface

Interface IsInterface {}

Implementation Classes

public ConcreteClassA implements IsInterface {

 InjectorA a, InjectorB c, InjectorC c;

 @Inject
 ConcreteClassA(InjectorA a, InjectorB b, InjectorC c) {
   this.a = a;
   this.b = b;
   .....
 }

}

public ConcreteClassB implements IsInterface {

 InjectorA a, InjectorB B, InjectorC C;

 @Inject
 ConcreteClassB(InjectorA a, InjectorB b, InjectorC c) {
   this.a = a;
   this.b = b;
   .....
 }

}

..and then I decide to use GWT deferred binding so in my GWT module.gwt.xml

//Pseudo XML Configuration
if (type is IsInterface) 
   if toggle == A then use ConcreteClass A else use ConcreteClassB

Now, when I try to run this. It won't work because GWT expected my Concrete Class A and B to have default 0 constructor. So, I tried the following on my concrete class

 @Inject
 InjectorA a; 
 @Inject
 InjectorB b;
 @Inject
 InjectorC c;

 ConcreteClassA() {

 }

which bypass the 0 constructor error but it gives me NullPointerException when I try to use a, b or c. One way to make it to work is to remove @Inject and use GWT.create() like so

 InjectorA a, InjectorB b, InjectorC c;

 ConcreteClassA() {
   this.a = GWT.create(InjectorA.class);
   .....
   .....
 }

This will work but what if my InjectorA, InjectorB and InjectorC have none 0 constructor and depended heavily on @inject. I dont want to go through all the classes to create 0 constructors and replace @inject with GWT.create(). There has to be a better way to do this. Am I missing something here?

possible duplicate of Gin Injection Inside Class Generated By Deferred Binding — Vjeetje

Infinity Infinity · Accepted Answer · 2013-08-26T19:22:25

Found a solution for this

interface IsInterface {
 @Inject
 void init(InjectorA a, InjectorB b, ...);
}

public ConcreteClassA implements IsInterface {

 InjectorA a, InjectorB c, InjectorC c;
 ConcreteClassA() {}
 @Override
 public void init(InjectorA a, InjectorB b, ..) {
  this.a = a;
  this.b = b;
  ....
 }

}

GWT Deferred Binding and Dependency Injection

1 Answers