Qualifying Spring dependency injection for field from superclass

Question

How I can inject my webServiceTemplate in the implementing class?

My example:

public abstract class AbstractConnector {

    protected WebServiceTemplate webServiceTemplate;

    protected Object send(Object message) {
        return webServiceTemplate.marshalSendAndReceive();

   }

}

And in my concrete implementation I would like to set my webServiceTemplate like this.

public class MyConnector extends AbstractConnector {

   @Resource(name = "myWebService")
   private WebServiceTemplate webServiceTemplate;
}

But this is not OK. If I call the send(), then I will get NPE because webServiceTemplate is null. How to set this dependency in implementation which will be accessible in the send() method?

Answer 1

It's best to avoid field injection whenever possible, and this is an example why. Constructor injection makes this simple:

public abstract class AbstractConnector {
    private final WebServiceTemplate webServiceTemplate;

    protected AbstractConnector(WebServiceTemplate webServiceTemplate) {
        this.webServiceTemplate = webServiceTemplate;
    }
}

@Service
public class MyConnector extends AbstractConnector {

    @Inject // or @Autowired
    public MyConnector(@Qualifier("myWebService") WebServiceTemplate webServiceTemplate) {
        super(webServiceTemplate);
    }
}