What is the difference between addTo and include in Java Dagger?

includes

indicates which module the current module belongs to. For example, this is useful for aggregating all of your modules statically:

@Module(
  includes = { AndroidModule.class, NetworkModule.class, StorageModule.class }
)
public class RootModule() {
}

// other file
objectGraph = ObjectGraph.create(new RootModule());

      

        
        
        
      

    

Instead of dynamic:

objectGraph = ObjectGraph.create(
     new AndroidModule(), 
     new NetworkModule(), 
     new StorageModule());

      

        
        
        
      

    

So making full use of compile-time graph validation.

addsTo

refers specifically to the relationship between parent and child modules. It indicates that the module is an extension of some module and is used as a parameter .plus()

. For example. with two modules:

@Module(
  //...
)
public class ParentModule() {
  //...
}

@Module(
  addsTo = { ParentModule.class },
  //...
)
public class ChildModule () {
  //...
}

      

        
        
        
      

    

this configuration means that parentGraph = ObjectGraph.create(new ParentModule());

you can then execute childGraph = parentGraph.plus(new ChildModule());

somewhere in your code to create an extended, usually short-lived child graph.