Injecting property using @Value to abstract class

Question

I have an abstract class in which I am trying to use the @Value annotation to inject value from a property file

public abstract class Parent {
     @Value ("${shared.val}")
     private String sharedVal;

     public Parent() {
        //perform common action using sharedVal
     }

}

@Component
public class ChildA extends Parent {
     Param a1;
     @Autowired
     public ChildA (Param a1) {
        super();
        this.a1 = a1;
     }
}

I am getting NullPointerException since sharedVal is not set. I tried adding @Component stereotype on the abstract class and still the same thing.

Can I inject value into abstract class this way? If not how can accomplish this?

Answer 1

I think you'll find the sharedVal is being set, but you're trying to use it too soon in the constructor. The constructor is being called (must be called) before Spring injects the value using the @Value annotation.

Instead of processing the value in the constructor, try a @PostContruct method instead, eg:

@PostConstruct
void init() {
    //perform common action using sharedVal
 }

(or alternatively, implement Spring's InitializingBean interface).