Guice with parents

Question

What do I do with Guice when I need to call a parent constructor that is also injectable? e.g. I have an abstract parent class that has a constructor that is injected with a

Answer 1

A better alternative is to use something similar to the strategy pattern to encapsulate all the fields the superclass wants to inject, and then the subclass can inject that. For example:

public abstract class Animal {
  /**
   * All injectable fields of the Animal class, collected together
   * for convenience.
   */
  protected static final class AnimalFields {
    @Inject private Foo foo;
    @Inject private Bar bar;
  }

  private final AnimalFields fields;

  /** Protected constructor, invoked by subclasses. */
  protected Animal(AnimalFields fields) {
    this.fields = fields;
  }

  public Foo getFoo() {
    // Within Animal, we just use fields of the AnimalFields class directly
    // rather than having those fields as local fields of Animal.
    return fields.foo;
  }

  public Bar getBar() {
    return fields.bar;
  }
}

public final class Cat extends Animal {
  private final Whiskers whiskers;

  // Cat's constructor needs to inject AnimalFields to pass to its superclass,
  // but it can also inject whatever additional things it needs.
  @Inject
  Cat(AnimalFields fields, Whiskers whiskers) {
    super(fields);
    this.whiskers = whiskers;
  }

  ...
}