How to dynamically retrieve a CDI dependency?

Question

I'm trying to dynamically retrieve a dependency for my Java code.

I know the class name, but I want to take the instance managed by the container, with proper indirect dependencies resolved.

For example:

class Foo {

    public static void foo() {
        Bar bar = (Bar) getDependency("com.example.Bar");
        bar.bar();
    }

}

class Bar {

     @Inject
     private Spam spam;

     public void bar() {
         spam.spam();
     }

}

I can't construct a Bar instance myself because I wouldn't be able to inject the correct Spam. So I want as if Foo had injected a Bar into it. I can't add a field like @Inject Bar bar because the exact name of the dependency varies in runtime.

Any way to do this?

I'm using WildFly 8.2.0.

Answer 1

You can do something like this:

public class Foo {

    @Inject BeanManager beanManager;

    public void foo() {
        Set<Bean<?>> beans = beanManager.getBeans(Bar.class);
        Bean<?> bean = beanManager.resolve(beans);
        CreationalContext<?> creationalContext = beanManager.createCreationalContext(bean);
        Bar bar = (Bar) beanManager.getReference(bean, Bar.class, creationalContext);   
    }
}

or maybe even simpler:

public class Foo {

    @Inject Instance<Object> instance;

    public void foo() {
        Bar bar = instance.select(Bar.class).get();
    }
}