In some instances, the type of bean we wish to inject into our code may be an interface or a Java superclass, but we may be interested in injecting a subclass or a class implementing the interface. For cases like this, CDI provides qualifiers we can use to indicate the specific type we wish to inject into our code.

A CDI qualifier is an annotation that must be decorated with the @Qualifier annotation. This annotation can then be used to decorate the specific subclass or interface. In this section, we will develop a Premium qualifier for our customer bean; premium customers could get perks that are not available to regular customers, for example, discounts.

Creating a CDI qualifier with NetBeans is very easy; all we need to do is go to File | New File, select the Contexts and Dependency Injection category, and select the Qualifier Type file type.

In the next step in the wizard, we need to enter a name and a package for our qualifier.

After these two simple steps, NetBeans generates...