Best practices for building large GWT applications Heiko Braun - - PowerPoint PPT Presentation

Best practices for building large GWT applications

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

• Decomposing a large GWT application
• Introducing project Errai

Decomposing a large GWT application

Example: JBoss SOA tooling

Challenge #1:Feature Set

• Different features per:
• Target runtime
• Development stage
• Project lifecycle
• Target audience

Solution #1: Compile-time composition

• Uses Deferred Binding [1] and plugin discovery
• Leverage Maven dependency sets
• Defer decision which components go into

application

• Allows ‘divide and conquer’ approach

[1] http://code.google.com/p/google-web-toolkit-doc-1-5/wiki/DevGuideDeferredBindingConcepts

Solution #1: Compile-time composition

Limitation #1: Component interplay

• Each plugin component isolated
• No interplay possible
• It would introduce dependencies
• Grouping by functionality vs. usability
• Technical split vs. conceptual split

(i.e process execution & reporting)

Challenge #2: Coupling between components

Challenge #2: Coupling between components

• Components “decorate” functionality
• i.e. Process Management & Reporting
• Dependencies may come and go
• Different feature set:
• Maturity (Beta vs. Final)
• Environment (staging vs. production)
• Profiles (authorization roles)

Solution #2: MVC

• Model-View-Controller ?
• Less coupled
• Enables interplay between UI plugin

components

• Still compile-time dependencies

(i.e controller to view)

Solution #2: Pub/Sub

• Messaging through publish /

subscribe

• Baseline on Messaging API
• Single, shared dependency
• Challenge: detyped, no contract

Challenge #3: UI coupled to services

• I.e. Report Tools (UI) requires BIRT Engine

(backend)

• Services may come and go:
• SOA promise
• Different product versions
• Target runtime derivations

• Bootstrap: “Give me a list of

capabilities”

• Performed when application starts
• Problem: Fixed initialization point
• Lazy Components?

Solution #3: Bootstrap

• Presence: “I need a SMTP service.

Notify me upon availability”

• Relies on messaging bus behind the

scenes

• Async, independent, durable

Solution #3: Blackboard

• All purpose solution: pub/sub
• Async communication already preferred
• Use it to:
• Decouple UI components
• Integrate backend services
• Break the request/response paradigm

Lessons learned

Introducing Project Errai

Project Errai

• Tackles the problems described earlier
• Consolidates JBoss GWT efforts
• Both R&D and actual product development
• Main components:
• Message Bus & Workspace framework

> http://jboss.org/errai

Message Bus

• Backbone to application

design

• Federated architecture
• Asynchronous & bi-

directional

• Broadcasting &

Conversations

• Built-in serialization
• Supports OpenHUB spec
• HTTP + NIO

Common, shared messaging API

Publisher Subscriber

Pub/Sub roles vs. tiers

• Subscriber defines target tier:
• client-server (client send)
• server-client (server push)
• client-client across server (browser to

browser)

• client-client w/o server (inter component)

Workspace framework

• UI environment for which to deploy your console
• Provides development infrastructure, documentation and

examples:

• Tear down barriers, ease of use
• Common, shared services, i.e:
• Authentication & Authorization
• Logging & Exception handling
• Allows composition at various stages:
• Sandbox, Project, Product

Workspaces API

(1) Component declaration

• Handles loading, initialization and access of UI components
• Uses maven dependencies, deferred Binding and auto-discovery

(2) Workspace assembly

Conclusion

• Presented patterns are solutions to coarse grained problems
• Also consider MVP

, GIN, etc: See Google I/O

• Message Bus has proven to be a good all-purpose solution
• Next big thing: Bring GWT to the enterprise Java community
• CDI integration (Tuesday, 1 June 2010, 15:00-15:50, Arena 3),
• JMS integration
• Portal / OpenSocial gadgets

Q&A

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