| = simple-cdi-interceptor |
| :jbake-date: 2016-09-06 |
| :jbake-type: page |
| :jbake-tomeepdf: |
| :jbake-status: published |
| |
| Example simple-cdi-interceptor can be browsed at https://github.com/apache/tomee/tree/master/examples/simple-cdi-interceptor |
| |
| = Simple CDI Interceptor |
| |
| Let's write a simple application that would allow us to book tickets for a movie show. As with all applications, logging is one cross-cutting concern that we have. |
| |
| (Relevant snippets are inlined but you can check out the complete code, from the links provided) |
| |
| How do we mark which methods are to be intercepted ? Wouldn't it be handy to annotate a method like |
| |
| |
| [source,java] |
| ---- |
| @Log |
| public void aMethod(){...} |
| |
| Let's create an annotation that would "mark" a method for interception. |
| |
| @InterceptorBinding |
| @Target({ TYPE, METHOD }) |
| @Retention(RUNTIME) |
| public @interface Log { |
| } |
| ---- |
| |
| |
| Sure, you haven't missed the @InterceptorBinding annotation above ! Now that our custom annotation is created, lets attach it (or to use a better term for it, "bind it" ) |
| to an interceptor. |
| |
| So here's our logging interceptor. An @AroundInvoke method and we are almost done. |
| |
| |
| [source,java] |
| ---- |
| @Interceptor |
| @Log //binding the interceptor here. now any method annotated with @Log would be intercepted by logMethodEntry |
| public class LoggingInterceptor { |
| @AroundInvoke |
| public Object logMethodEntry(InvocationContext ctx) throws Exception { |
| System.out.println("Entering method: " + ctx.getMethod().getName()); |
| //or logger.info statement |
| return ctx.proceed(); |
| } |
| } |
| ---- |
| |
| |
| Now the @Log annotation we created is bound to this interceptor. |
| |
| That done, let's annotate at class-level or method-level and have fun intercepting ! |
| |
| |
| [source,java] |
| ---- |
| @Log |
| @Stateful |
| public class BookShow implements Serializable { |
| private static final long serialVersionUID = 6350400892234496909L; |
| public List<String> getMoviesList() { |
| List<String> moviesAvailable = new ArrayList<String>(); |
| moviesAvailable.add("12 Angry Men"); |
| moviesAvailable.add("Kings speech"); |
| return moviesAvailable; |
| } |
| public Integer getDiscountedPrice(int ticketPrice) { |
| return ticketPrice - 50; |
| } |
| // assume more methods are present |
| } |
| ---- |
| |
| |
| The `@Log` annotation applied at class level denotes that all the methods should be intercepted with `LoggingInterceptor`. |
| |
| Before we say "all done" there's one last thing we are left with ! To enable the interceptors ! |
| |
| Lets quickly put up a [beans.xml file] |
| |
| |
| [source,xml] |
| ---- |
| <beans> |
| <interceptors> |
| <class>org.superbiz.cdi.bookshow.interceptors.LoggingInterceptor |
| </class> |
| </interceptors> |
| </beans> |
| ---- |
| |
| |
| in META-INF |
| |
| |
| Those lines in beans.xml not only "enable" the interceptors, but also define the "order of execution" of the interceptors. |
| But we'll see that in another example on multiple-cdi-interceptors. |
| |
| Fire up the test, and we should see a 'Entering method: getMoviesList' printed in the console. |
| |
| = Tests |
| Apache OpenEJB 4.0.0-beta-2 build: 20111103-01:00 |
| http://tomee.apache.org/ |
| INFO - openejb.home = /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors |
| INFO - openejb.base = /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors |
| 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: /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors/target/classes |
| INFO - Beginning load: /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors/target/classes |
| INFO - Configuring enterprise application: /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors |
| INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container) |
| INFO - Auto-creating a container for bean cdi-simple-interceptors.Comp: Container(type=MANAGED, id=Default Managed Container) |
| INFO - Configuring Service(id=Default Stateful Container, type=Container, provider-id=Default Stateful Container) |
| INFO - Auto-creating a container for bean BookShow: Container(type=STATEFUL, id=Default Stateful Container) |
| INFO - Enterprise application "/media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors" loaded. |
| INFO - Assembling app: /media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors |
| INFO - Jndi(name="java:global/cdi-simple-interceptors/BookShow!org.superbiz.cdi.bookshow.beans.BookShow") |
| INFO - Jndi(name="java:global/cdi-simple-interceptors/BookShow") |
| INFO - Created Ejb(deployment-id=BookShow, ejb-name=BookShow, container=Default Stateful Container) |
| INFO - Started Ejb(deployment-id=BookShow, ejb-name=BookShow, container=Default Stateful Container) |
| INFO - Deployed Application(path=/media/fthree/Workspace/open4/openejb/examples/cdi-simple-interceptors) |
| Entering method: getMoviesList |