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Introduction to Seam Applications
 

Introduction to Seam Applications

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An introduction to JBoss Seam framework

An introduction to JBoss Seam framework

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    Introduction to Seam Applications Introduction to Seam Applications Presentation Transcript

    • Introduction to Seam Applications Nuwan Gunarathna www.geveo.com
    • Agenda
      • Common WebApp Development Patterns.
      • Why Seam?
      • Features.
      • CRUD App demo with seam-gen.
      • Q&A
    • Today’s Web Applications
      • Too many layers
        • Too many Integration Points
        • Too much Xml configuration
      • For new features, You have to lean new Frameworks
      • “ Stateless” Architecture
      • JSF falls short – Not fully enough for Web 2.0
      • Not a platform, merely a set of libraries and wrappers
      • Documentation is not at one place(Too many dependent frameworks)
    • Why Seam?
      • To provide a Complete solution for Java Web Application
        • Whithin an Application
      • Is it good? Yes.
      Gavin King
    • Some Good Reasons
      • Stateful Wep Applications
        • All components are inherently stateful – no need state management Code
      • Configuration by Exception( convention over configuration )
        • Idea is to have a common-sense default behaviors for components
      • Gluing JSF and EJB3 across framework boundaries.
        • Collapse artificial façade object layer in between
      • Annotation based integration
      • Gives correct wayt to use ORM
        • Lazy loading just works fine: Eliminate most encountered Exception with stateless frameworks all the time
        • Only framework that support lazy loading correctly in web application
    • Some Good Reasons cont..
      • No more DTOs to write
      • POJO as business services
        • No framework interfaces, No Abstract classes
        • Using dependency bijection
      • App Generator via seam-gen (aka scaffolding)
      • It makes persistence a breeze
      • Annotations over XML, end to end
      • Automated integration testing using TestNg and JUnit
      • And many more … (Rules Engine, BPM, Ajax Support, Pdf, E-mail, RESTful …)
      • Open source. Open standards. Future of Java EE
    • Layers in Seam View (JSF/Wicket/GWT/Flex etc.,) Business Layer (SFSB/SLSB/POJO) DB Persistence Layer (Entities) Hey, No Integration Layer!
        Seam exposes Business Layer objects and their attributes on the front-end using EL expressions.
      • No DAOs
      • No DTOs
    • Contextual Components
      • Most of the problems relate to state management
      • Traditional contexts for Java Servlets focused on technology instead of on application
      • EJB itself has no strong model of state management
      • We need a richer context model that includes “logical” context
      • We should be able to use annotations everywhere
      • An EJB should be able to be a JSF managed bean (vice versa)
      • Main idea: realization of desktop-like wizards and dialogs, possibly in parallel
      • It makes sense to think of binding EJB components directly to the JSF view
    • The Seam Context Model *source: www.reverttoconsole.com
    • Conversations
      • Conversations are not that exciting until you really start thinking about them:
      • Multi-window operation
      • “ Workspace Management”
      • Stack of continuable states (nested conversation)
      • No more HttpSession object
        • Reduce codes and memory leaks
      • Avoid unexpected behaviors with multiple browser windows
    • Conversations Cont..
      • Allows multiple concurrent state containers for a single user over HTTP session
      • Each conversation resides in its own Browser or Tab
      User Session Browser1 Browser2 Browser3 User Concurrent Conversations C3 C2 C1
    • Page Flow/Navigation Rules
      • Seam specific file to enhance page navigation
        • pages.xml integrates stateful components
      • Manage complicated navigation flows based on current state of the application
      • Define navigation rules for each page
      • Flow is based on events and conditions
    • New Programing Patterns
      • EntityHome
        • Manage persistence state of a single Object
        • CRUD operations
        • • persist();
        • • getInstance();
        • • update();
        • • remove();
      • EntityQuery
        • Manage JP/EJB QL(Query Language) result se t
    • Ajax Support
      • Seam's totally unique concurrency model and state-management model was conceived and designed with AJAX in mind.
      • Page Wide Support (region, zone)
        • Add support to existing components
        • Sub view processing
        • Partial tree rendering, partial page refresh
      • Component Wide
        • Ajaxified components
        • Client validations
    • Integration Testing
      • Seam components can easily be tested in TestNG or Junit
      • The JBoss Embeddable EJB3 container is a great platform for integration testing: perform an end to end testing in it’s own embeddable container -- in a single unit test!
      • Test he entire flow of a request or conversation
      • Test all layers of Java code in the application, from presentation to persistence.
    • Seam-gen
      • Generate a project structure with build
      • Generate CRUD views
      • Reverse engineering of POJOs
      • Entity model validations enforced with ajax feedback
      • Generates Ant build script itself
      • Ready made project files for eclipse, netbeans, idea
      • Basic page level authorization
      • Datasource creation and configuring persistence layer
      • Richfaces Ui components
    • Other Technologies?
      • But what about Spring, Spring MVC, Grails, hibernate stack or JSF?
      • Grails ... Probably.
        • Leverage the Groovy programming language
      • But Seam is:
        • An “application stack” not a “web framework”
        • A unified development platform of {programming model, frameworks, best practices and tooling}
    • Resources
        • Reference docs, more than 30 examples, forums and best overall place - www.seamframework.org
        • Richfaces 3.3 - http://www.jboss.org/jbossrichfaces/docs/
        • Richfaces book – Practical Richfaces (Max Katz)
        • JSF 2 (includes “seam” like features) - http://nejug.org/events/show/91
        • EJB 3.1 - http://jcp.org/en/jsr/detail?id=318
        • Seam Books – Seam in Action (Dan Allen) & Seam Framework – Experience the evolution of Java EE (Jacob Orshalick)
        • Tools: JBoss Tools for Eclipse. Intellij and Netbeans also have excellent support for Seam