Question

Given a class :

public ClassA {
    @Autowired
    @SomeAnnotation("foo")
    private ClassB bar;
}

@Component
@Scope(prototype)
public ClassB {
    private String someString;
}

I would like to write some bean processor (post construct…) that can at ClassB construction time can access the @SomeAnnotation on the intances that ClassB is getting injected into so that I can set the value of someString to “foo”.

I know this isn’t very IoC and I’m going to guess it cannot be done.

Answer 1

You might be able to do something like this with a @PostConstruct of ClassA:

@PostConstruct
public void postConstruct(){
  SomeAnnoation someAnnotation =  this.getClass().getField("bar").getAnnotation(SomeAnnotation.class);
  bar.someString(someAnnotation.value());
}

Update: – General solution using a BeanPostProcessor :

public class SomeAnnotationFieldInitalizer implements BeanPostProcessor{

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        Field[] fields = bean.getClass().getFields();
        if (fields!=null){
            for (Field field:fields){
                SomeAnnotation someAnnotation = field.getAnnotation(SomeAnnotation.class);
                if (someAnnotation!=null){
                    try {
                        ReflectionUtils.makeAccessible(field);
                        field.set(bean, someAnnotation.value());
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return bean;
    }
}