On Wed, May 4, 2011 at 11:42 AM, Thiago H. de Paula Figueiredo
<thiag...@gmail.com> wrote:
> I wouldn't call this composition (IMHO it's a class transformation), but
> this is really cool and shows how flexible, reusable and all-around awesome
> Tapestry is. :)
Semantics. The class transformation, informed by the annotation,
drives the composition, just as the Java extends keyword drives
inheritance.
>
> On Wed, 04 May 2011 15:34:48 -0300, Adam Zimowski <zimowsk...@gmail.com>
> wrote:
>
>> Another lovely day with Tapestry! Inspired by Taha's blog entry on
>> Tapestry Magic, our app instead of this mess:
>>
>> public class OrderHistoryPage extends AuthenticatedPage
>>
>> looks sexy like never before with this:
>>
>> @RequiresLogin(ssoClass= UserUiBean.class, pageClass= Login.class)
>> public class OrderHistoryPage extends BasePage
>>
>> Here are the pieces:
>>
>> Custom Annotation
>> /**
>> * Tells Tapestry that a page requires authenticated user. If a page is
>> * annotated with this, and user is not logged in, that page shall
>> redirect
>> * to a login screen instead of rendering itself.
>> *
>> * @author Adam Zimowski
>> */
>> @Target({ElementType.TYPE})
>> @Retention(RetentionPolicy.RUNTIME)
>> @Documented
>> public @interface RequiresLogin {
>>
>> /**
>> * Class whose instance lives in session and represents
>> authenticated user.
>> */
>> Class<?> ssoClass();
>>
>> /**
>> * Page class to which Tapestry should redirect guests instead of
>> * displaying secured page
>> */
>> Class<? extends BasePage> pageClass();
>> }
>>
>> Annotation Worker
>> /**
>> * Transforms page classes annotated with {@link RequiresLogin} adding
>> advice
>> * which tests if the user is logged in, then redirects to login page if
>> user
>> * is guest.
>> *
>> * @author Adam Zimowski
>> */
>> public class RequiresLoginAnnotationWorker implements
>> ComponentClassTransformWorker {
>>
>> private final TransformMethodSignature ONACTIVATE_SIGNATURE =
>> new TransformMethodSignature(
>> 0, "java.lang.Object", "onActivate", null, null);
>>
>> private Logger log =
>>
>> LoggerFactory.getLogger(RequiresLoginAnnotationWorker.class);
>>
>> private ApplicationStateManager asm;
>>
>>
>> public RequiresLoginAnnotationWorker(ApplicationStateManager aAsm)
>> {
>> asm = aAsm;
>> }
>>
>> @Override
>> public void transform(ClassTransformation aTransformation,
>> MutableComponentModel aModel) {
>>
>> RequiresLogin annotation = aTransformation
>> .getAnnotation(RequiresLogin.class);
>>
>> if (annotation == null) {
>> return;
>> }
>>
>> final Class<?> ssoClass = annotation.ssoClass();
>> final Class<?> pageClass = annotation.pageClass();
>>
>> if(log.isDebugEnabled()) {
>> log.debug(".. transforming {} ..",
>> aTransformation.getClassName());
>> }
>>
>> TransformMethod methodTransformer = null;
>> try {
>> methodTransformer =
>>
>> aTransformation.getOrCreateMethod(ONACTIVATE_SIGNATURE);
>> }
>> catch(Throwable t) {
>> throw new
>> RuntimeException(RequiresLogin.class.getSimpleName() +
>> " annotation requires package scope " +
>> "[ Object onActivate() ] method.", t);
>> }
>>
>> methodTransformer.addAdvice(
>> new ComponentMethodAdvice() {
>> public void
>> advise(ComponentMethodInvocation invocation) {
>> invocation.proceed();
>> if(!asm.exists(ssoClass)) {
>>
>> if(log.isDebugEnabled()) {
>> log.debug(
>>
>> "redirecting to {} page ...",
>>
>> pageClass.getSimpleName());
>> }
>>
>> invocation.overrideResult(pageClass);
>> }
>> }
>> }
>> );
>> }
>> }
>>
>> Service Contribution
>> @Contribute(ComponentClassTransformWorker.class)
>> public void contributeComponentClassTransformWorker(
>> OrderedConfiguration<ComponentClassTransformWorker>
>> aWorkers) {
>>
>> aWorkers.addInstance(
>> RequiresLogin.class.getSimpleName(),
>> RequiresLoginAnnotationWorker.class,
>> "before:OnEvent");
>> }
>>
>> Page class usage:
>>
>> @RequiresLogin(ssoClass = UserUiBean.class, pageClass = Login.class)
>> public class UserProfilePage extends BasePage { ...
>>
>>
>> Feel free to re-use! Para-Ta-Ta-Taaaaa ........... I'M LOVIN' IT !!!!!
>>
>> Adam
>>
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>>
>
>
> --
> Thiago H. de Paula Figueiredo
> Independent Java, Apache Tapestry 5 and Hibernate consultant, developer, and
> instructor
> Owner, Ars Machina Tecnologia da Informação Ltda.
> Consultor, desenvolvedor e instrutor em Java, Tapestry e Hibernate
> Coordenador e professor da Especialização em Engenharia de Software com
> Ênfase em Java da Faculdade Pitágoras
> http://www.arsmachina.com.br
>
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>
>
--
Howard M. Lewis Ship
Creator of Apache Tapestry
The source for Tapestry training, mentoring and support. Contact me to
learn how I can get you up and productive in Tapestry fast!
(971) 678-5210
http://howardlewisship.com
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