Contexts and Dependency Injection for the Java EE Platform: Advanced Topics - The Java EE 6 Tutorial: Advanced Topics - page 261

To make a bean available for lookup, injection, or EL resolution using this mechanism,
give it a javax.enterprise.inject.Alternative annotation and then use the
alternative element to specify it in the beans.xml file.
For example, you might want to create a full version of a bean and also a simpler version
that you use only for certain kinds of testing. The example described in “ The encoder
Example: Using Alternatives ” on page 265 contains two such beans, CoderImpl and
TestCoderImpl . The test bean is annotated as follows:
Click here to view code image
@Alternative
public class TestCoderImpl implements Coder { ... }
The full version is not annotated:
public class CoderImpl implements Coder { ... }
The managed bean injects an instance of the Coder interface:
@Inject
Coder coder;
The alternative version of the bean is used by the application only if that version is de-
clared as follows in the beans.xml file:
Click here to view code image
<beans ... >
<alternatives>
<class>encoder.TestCoderImpl</class>
</alternatives>
</beans>
If the alternatives element is commented out in the beans.xml file, the Coder-
Impl class is used.
You can also have several beans that implement the same interface, all annotated @Al-
ternative . In this case, you must specify in the beans.xml file which of these al-
ternative beans you want to use. If CoderImpl were also annotated @Alternative ,
one of the two beans would always have to be specified in the beans.xml file.