Introduction to seam_applications_formated
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Introduction to seam_applications_formated Introduction to seam_applications_formated 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