| = CDI Alternative and Stereotypes |
| :index-group: CDI |
| :jbake-type: page |
| :jbake-status: published |
| |
| == Introduction |
| CDI is a revolution for the Java EE world. This specification is the best one to avoid coupling between classes. |
| |
| This example simply aims to override bindings at runtime to simplify mocking work. |
| |
| It uses two kind of mocks: |
| |
| 1) a mock with no implementation in the classloader |
| |
| 2) a mock with an implementation in the classloader |
| |
| The mock answer from CDI is called _alternative_. |
| |
| Annotating `@Alternative` a class will mean it will used as the implementation if there is no other implementation |
| or if it is forced (through `META-INF/beans.xml`). |
| |
| == Code Explanation |
| |
| === Main Code |
| |
| We use an EJB `Journey` to modelize a journey where the vehicle and the society can change. Here an EJB is used |
| because it simplifies the test. A jouney wraps the vehicle and society information. |
| |
| We define two interfaces to inject into the `Journey` EJB: `Vehicle` and `Society`. |
| |
| Finally we add an implementation for `Society` interface: `LowCostCompanie`. |
| |
| If we stop here, the `Journey` object will not be able to be created because there is no `Vehicle` implementation is available. |
| |
| NOTE: if we do have a `Vehicle` implementation, the injected Society should be `LowCostCompanie`. |
| |
| === Test Code |
| |
| The goal here is to test our `Journey` EJB. So we have to provide a `Vehicle` implementation: `SuperCar`. |
| |
| We want to force the `Society` interface to be the `AirOpenEJB` implementation for our test. |
| |
| One solution could simply be to add `@Alternative` annotation on `AirOpenEJB` and activate it through |
| the `META-INF/beans.xml` file. |
| |
| Here we want to write more explicit code. So we want to replace the `@Alternative` annotation by `@Mock` one. |
| |
| So we define an `@Mock` annotation for classes, resolvable at runtime as a stereotype (`@Stereotype`) |
| that replaces `@Alternative`. |
| |
| Here is the annotation: |
| |
| [source,java,numbered] |
| ---- |
| @Stereotype // we define a stereotype |
| @Retention(RUNTIME) // resolvable at runtime |
| @Target(TYPE) // this annotation is a class level one |
| @Alternative // it replace @Alternative |
| public @interface Mock {} |
| ---- |
| |
| NOTE: you can add more CDI annotations after `@Alternative` and it will get the behavior expected (the scope for instance). |
| |
| So now we have our `@Mock` annotation which is a stereotype able to replace the `@Alternative` annotation when it |
| added to our mocks. |
| |
| If you run it now you'll have this exception: |
| |
| [source,java,numbered] |
| ---- |
| javax.enterprise.inject.UnsatisfiedResolutionException: Api type [org.superbiz.cdi.stereotype.Vehicle] is not found with the qualifiers |
| Qualifiers: [@javax.enterprise.inject.Default()] |
| for injection into Field Injection Point, field name : vehicle, |
| Bean Owner : [Journey, Name:null, WebBeans Type:ENTERPRISE, API Types:[java.lang.Object,org.superbiz.cdi.stereotype.Journey], |
| Qualifiers:[javax.enterprise.inject.Any,javax.enterprise.inject.Default]] |
| ---- |
| |
| It means the stereotype is not activated. To do it simply add it to your `META-INF/beans.xml`: |
| |
| <alternatives> |
| <stereotype>org.superbiz.cdi.stereotype.Mock</stereotype> |
| </alternatives> |
| |
| NOTE: if you don't specify `AirOpenEJB` as `@Alternative` (done through our mock annotation) you'll get this exception: |
| |
| source,java,numbered] |
| ---- |
| Caused by: javax.enterprise.inject.AmbiguousResolutionException: |
| There is more than one api type with : org.superbiz.cdi.stereotype.Society with qualifiers : |
| Qualifiers: [@javax.enterprise.inject.Default()] for injection into Field Injection Point, field name : society, |
| Bean Owner : [Journey, Name:null, WebBeans Type:ENTERPRISE, |
| API Types:[org.superbiz.cdi.stereotype.Journey,java.lang.Object], |
| Qualifiers:[javax.enterprise.inject.Any,javax.enterprise.inject.Default]] |
| found beans: |
| AirOpenEJB, Name:null, WebBeans Type:MANAGED, |
| API Types:[org.superbiz.cdi.stereotype.Society,org.superbiz.cdi.stereotype.AirOpenEJB,java.lang.Object], |
| Qualifiers:[javax.enterprise.inject.Any,javax.enterprise.inject.Default] |
| LowCostCompanie, Name:null, WebBeans Type:MANAGED, |
| API Types:[org.superbiz.cdi.stereotype.Society,org.superbiz.cdi.stereotype.LowCostCompanie,java.lang.Object], |
| Qualifiers:[javax.enterprise.inject.Any,javax.enterprise.inject.Default] |
| ---- |
| |
| which simply means two implementations are available for the same injection point (`Journey.society`). |
| |
| == Conclusion |
| |
| With CDI it is really easy to define annotations with a strong meaning. You can define business annotations |
| or simply technical annotations to simplify your code (as we did with the mock annotation). |
| |
| NOTE: if you used qualifiers to inject `Society` objects you could have put all these qualifiers on |
| the mock class or defined a `@SocietyMock` annotation to be able to inject the same implementation for |
| all qualifiers in your tests. |
| |
| == Output |
| |
| ---- |
| Running org.superbiz.cdi.stereotype.StereotypeTest |
| Apache OpenEJB 7.0.0-SNAPSHOT build: 20111030-07:54 |
| http://tomee.apache.org/ |
| INFO - openejb.home = /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes |
| INFO - openejb.base = /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes |
| INFO - Using 'javax.ejb.embeddable.EJBContainer=true' |
| INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service) |
| INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager) |
| INFO - Found EjbModule in classpath: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes/target/test-classes |
| INFO - Found EjbModule in classpath: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes/target/classes |
| INFO - Beginning load: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes/target/test-classes |
| INFO - Beginning load: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes/target/classes |
| INFO - Configuring enterprise application: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes |
| INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container) |
| INFO - Auto-creating a container for bean cdi-alternative-and-stereotypes_test.Comp: Container(type=MANAGED, id=Default Managed Container) |
| INFO - Configuring Service(id=Default Singleton Container, type=Container, provider-id=Default Singleton Container) |
| INFO - Auto-creating a container for bean Journey: Container(type=SINGLETON, id=Default Singleton Container) |
| INFO - Enterprise application "/opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes" loaded. |
| INFO - Assembling app: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/cdi-alternative-and-stereotypes_test.Comp!org.apache.openejb.BeanContext$Comp") |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/cdi-alternative-and-stereotypes_test.Comp") |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/cdi-alternative-and-stereotypes.Comp!org.apache.openejb.BeanContext$Comp") |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/cdi-alternative-and-stereotypes.Comp") |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/Journey!org.superbiz.cdi.stereotype.Journey") |
| INFO - Jndi(name="java:global/cdi-alternative-and-stereotypes/Journey") |
| INFO - Jndi(name="java:global/EjbModule162291475/org.superbiz.cdi.stereotype.StereotypeTest!org.superbiz.cdi.stereotype.StereotypeTest") |
| INFO - Jndi(name="java:global/EjbModule162291475/org.superbiz.cdi.stereotype.StereotypeTest") |
| INFO - Created Ejb(deployment-id=cdi-alternative-and-stereotypes_test.Comp, ejb-name=cdi-alternative-and-stereotypes_test.Comp, container=Default Managed Container) |
| INFO - Created Ejb(deployment-id=cdi-alternative-and-stereotypes.Comp, ejb-name=cdi-alternative-and-stereotypes.Comp, container=Default Managed Container) |
| INFO - Created Ejb(deployment-id=org.superbiz.cdi.stereotype.StereotypeTest, ejb-name=org.superbiz.cdi.stereotype.StereotypeTest, container=Default Managed Container) |
| INFO - Created Ejb(deployment-id=Journey, ejb-name=Journey, container=Default Singleton Container) |
| INFO - Started Ejb(deployment-id=cdi-alternative-and-stereotypes_test.Comp, ejb-name=cdi-alternative-and-stereotypes_test.Comp, container=Default Managed Container) |
| INFO - Started Ejb(deployment-id=cdi-alternative-and-stereotypes.Comp, ejb-name=cdi-alternative-and-stereotypes.Comp, container=Default Managed Container) |
| INFO - Started Ejb(deployment-id=org.superbiz.cdi.stereotype.StereotypeTest, ejb-name=org.superbiz.cdi.stereotype.StereotypeTest, container=Default Managed Container) |
| INFO - Started Ejb(deployment-id=Journey, ejb-name=Journey, container=Default Singleton Container) |
| INFO - Deployed Application(path=/opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes) |
| INFO - Undeploying app: /opt/dev/openejb/openejb-trunk/examples/cdi-alternative-and-stereotypes |
| ---- |
