Saturday, February 23, 2013
actor-frameworks for the jvm gain more popularity every day. even with actor-frameworks you have to be careful with shared state. however, if you have a java-ee application, you can (re-)use stateless services in your actors easily. one use-case is to resolve transactional beans (ejbs, cdi-beans which are annotated e.g. with @Transactional, ...) in an actor and invoke methods on them to access a database.
with an ee-application-server like tomee that works out-of-the-box. you just have to bootstrap an actor-framework (like akka, jetlang,...) and use the std. java-ee api to lookup the bean/s.
if you are interested in using transactional cdi beans, you can use the jpa-module provided by apache deltaspike v0.4+ (note: those transactions don't span across actors). for using @Transactional, you just have to follow the documentation and you are done. that's usually a short story. but...
if you would like to use @Singleton or @ApplicationScoped beans and you are using the openwebbeans-web module of owb v1.1.x, you need an additional plugin (due to OWB-785). in such cases just get https://github.com/os890/owb-contexts_service-addon.git, build it and add it as runtime dependency to your project.
-> you are done (there is no additional api you have to use).
apache deltaspike provides some nice helpers (like BeanProvider#getContextualReference to resolve cdi-beans), interceptors (like @Transactional), scopes (like @TransactionScoped) and much more...