Abstract or default method annotated with @Inject JAVA-W1075

Abstract or default methods should not be annotated with @Inject.

As per the JSR-330 specification, @Inject shouldn't be applied to abstract and default methods. When marking an abstract method as @Injectable, the programmer believes that all the methods that inherit from it will be injectable. This is not the case at all; a method that only inhertis from an @Inject method but isn't itself marked as @Inject will not be injected. So is the case with default methods defined in interfaces. For this reason, it is advised that you only use the @Inject annotation on concrete methods.

Bad Practice

import javax.inject.Inject;

abstract public class Klass {
    @Inject
    public abstract int doStuff();
}

or in default methods:

import javax.inject.Inject;

public interface IFace {
    @Inject
    default public int doStuff() {
        //..default implementation here
    }
}

Recommended

Remove @Inject from abstract and default methods. Instead, apply them only on concrete implementations.

import javax.inject.Inject;

abstract public class Klass {
    public abstract int doStuff();
}

// Somewhere else in the codebase.
public class ConcreteKlass extends Klass {
    @Inject
    @Override
    public int doStuff() {
        // Implementation follows.
    }
}

References

• JSR-330 Dependency Injection Standard - @Inject Documentation