GWT, CDI & JAX-RS A match made in heaven Heiko Braun - PowerPoint PPT Presentation

GWT, CDI & JAX-RS “A match made in heaven” Heiko Braun <hbraun@redhat.com>

About me • Heiko Braun • Senior Software Engineer JBoss / Red Hat • 4 years JBoss, 12 years industry • Focus on SOA, BPM, GWT • Contributor: JBossWS, jBPM, Riftsaw, Errai, SAM, Savarra > http://jboss.org

Topics • GWT ecosystem • Integrating with CDI • When to use JAX-RPC

GWT ecosystem

GWT: Strong client side • GWT SDK: Tools & API to build Ajax clients & frameworks • Integration capabilities: - GWT RPC - XHR (Request Builder) • Data formats: JSON, XML • Rich set of widget libraries: - Mosaic, Smart GWT, etc

GWT: Weak server side • Service implementation choice: - rely on GWT RPC - or handle the low level protocol manually • Existing domain & component model? - Adapters, DTO’s, parallel hierarchy, etc - TX, Security, etc • A lot of boilerplate needs to be written

Backend implementation options

Java EE choices • CDI: Context and dependency injection for the EE platform (http://jcp.org/en/jsr/summary?id=299) • Java API for RESTful web services (http://jcp.org/en/jsr/detail?id=311) • Both part of EE 6

Relation to Errai • CDI integration build on Errai (http://jboss.org/errai) • Integration is actually an extension to Errai and vice versa • Knowledge about Errai Message Bus helpful, but not mandatory

GWT & CDI

GWT & CDI goals • Similar to GWT -RPC: • re-use domain model • transparent wire protocol (serialization) • In addition to GWT -RPC: • Bypass the servlet tier (merely transport) • Deep integration with EE component model • Richer programming model & reduction of boiler plate

CDI Concepts • Portable Extensions • Integration point when container bootstraps • Create beans, annotation processing, meta data modifications • Scope & Lifecycle • ApplicationScoped, RequestScoped, ConversationScoped • Bean context & reference • Lookup and instance (reference) creation 12

GWT & CDI Samples

Using Pub/Sub GWT Client • Most low level use cases (Errai Bus, Pub/Sub) • Similar to MessageDriven Bean (actual maps to it) CDI Component • Service implementation fully managed by CDI container • Message Bus instance injected 14

Exposing RPC endpoints GWT Client • Exposes a typed interface • Similar to EJB Session beans (maps to it) CDI Component • RPC style, type safe client API Remote interface 15

Working with CDI events GWT Client • Bi-directional event exchange • Discriminate on: - Event Type - Qualifier Annotations CDI Component • Exposes high level CDI client API • Integrate with default and custom CDI events 16

When to integrate with CDI • Benefits of Java EE 6 and GWT as an alternative view layer technology • Concise Java component model • Tool chain: GWT, EJB, CDI, JPA, JCA, JMS 17

GWT & JAX-RPC

GWT & JAX-RPC goals • RESTful web services: - RESTful API: open to non-java clients - Intermediaries: proxies, gateways, firewalls - [...] (See other Jazoon talks on this topic) • Expose low level protocol with a decent API • Directly expose XML, HTML from other resources - BIRT reporting (mashup, iframe) - Use of XML documents • Integrate with XHR (RequestBuilder) • Reuse domain model (serialization)

JAX-RPC Concepts @Path("/customerservice/") @Produces("application/xml") public class CustomerService { @GET @Path("/customers/{id}") @Produces("application/json") public Customer getCustomer( @PathParam("id") String id) { ...... } @PUT @Path("/customers/{id}") @Consumes("application/xml") public Response updateCustomer(@PathParam("id") Long id, Customer customer) { ...... } @POST @Path("/customers") public Response addCustomer(Customer customer) { ...... } @DELETE @Path("/customers/{id}/") public Response deleteCustomer(@PathParam("id") String id) { ...... } }

GWT & JAX-RPC samples

Request a JAX-RPC resource GWT Client Server Resource

Conclusion • CDI integration probably most reasonable choice for within EE 6 environments • Integration & boilerplate missing: Errai [1] to the rescue • JAX-RPC is more open, but very low level. Still better then writing your own servlet code • Remember: You can mix and match JAX-RPC and CDI within the same components (at least on JBoss 6) [1] http://anonsvn.jboss.org/repos/errai/projects/weld-integration/trunk/

Q&A > http://jboss.org/errai > http://errai-blog.blogspot.com/

Appendix A: Errai Message Bus

Errai Basics • Backbone to application design • Federated architecture • Asynchronous & bi- directional • Supports POJO serialization • Common shared API • Supports OpenHUB spec • HTTP + NIO

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