如何再次注入产品

Question

Using javaee beans, is there possibility to inject properties again if they are, for example, null?

My simplified code:

Service makes rest request to another service, and it get host property from a PropertyProduces that takes it from a third config service. For example, when I first time making RestService.call() , config service is disabled, so it return host=null. I am not able to callAnotherService properly, this is fine. Then config service became enabled, but when I make second RestService.call() , host is already null and it even do not want to get to PropertyProduces.produceString

Can I somehow intercept usage of host property, check if it is null and force it to inject from Produces again?

@ApplicationScoped
public class Service {
    @Property
    private final String host;

    public void callAnotherService() {
        callRestMethod(host)
    }
}

@ApplicationScoped
public class PropertyProduces {

    @Inject
    private Config config;

    @Property
    @Produces
    public String produceString(InjectionPoint ip) {
        return this.config.getString(ip.getMember().getName());
    }
}

@Path("/")
@ApplicationScoped
public class RestService {
    @Inject
    private Service service;
  
    @POST
    @Path("/call")
    public Response call(Request request)
    {
        this.service.callAnotherService();
    }
}

I know I can change class Service to @RequestScoped, so at different rest requests will be created different Service instances and host will be produces everytime. But is there another posibility, somehow changing PropertyProduces or making Interceptors?

Answer 1

You should try to use dynamic bean selection on your Service class:

 @Inject
 @Property
 Instance<String> instance;

and then in your Service method you can do:

public void callAnotherService() {
     String host = instance.get();
     callRestMethod(host)
}

More references at https://docs.oracle.com/javaee/7/api/javax/enterprise/inject/Instance.html