org.seedstack.business.domain

Annotation Type DomainPolicy

@Documented
 @Retention(value=RUNTIME)
 @Target(value={TYPE,ANNOTATION_TYPE})
public @interface DomainPolicy

A policy is used to encapsulate a varying business rule or process in a separate object. Multiple versions of the policy object represent different ways the process can be done.

This annotation can be applied to an interface to declare a domain policy. Any class implementing the annotated interface will be registered by the framework as an implementation of this policy.

When a policy interface has multiple implementations, it is necessary to differentiate them by using a different javax.inject.Qualifier annotation on each. This qualifier can then be used at the injection point to specify which implementation is required.

Considering the following policy:

  @DomainPolicy
  public interface SomePolicy {
     double computeSomething(String someParameter);
  }
 

Two different implementations can be declared as follows:

  @Named("variantA")
  public class SomePolicyVariantA {
      @Override
      public double computeSomething(String someParameter) {
          // implement variant A logic
      }
  }

  @Named("variantB")
  public class SomePolicyVariantB {
      @Override
      public double computeSomething(String someParameter) {
          // implement variant B logic
      }
  }
 

The "B variant" implementation can then be injected as follows:

 public class SomeClass {
      @Inject
      @Named("variantB")
      SomePolicy somePolicy;
 }