Understanding JBoss Seam Registration example

 

What is JBoss Seam?

  • It is Framework that integrates JSF, EJB 3/POJO and JPA very well.  JSF is a component technology that allows developers to reuse components. There are many JSF component providers, such as Rich faces and Ice faces.  Java Persistence API (JPA) is java standard for mapping java object to a relational database.
  • Seam is also a context based dependency injection framework.  Seam allows developers to inject Seam container managed object into Seam component.  Seam container is responsible for creating and managing the life cycle of the object.  Dependency injection framework promotes loose coupling design pattern.  The client of a java object is not responsible for the creating of the object. Therefore, the client is not dependent on the implementation of the java object.
  • Seam enhanced JSF. It provides a whole solution to an entire web application project.  For example, it provides many extra features such as scheduler and email integration. 

 

The Registration example

JBoss Seam distribution comes with many sample applications.  The registration example allows users to store his username, real name and password in the database.  Blow is a screen shoot from Seam Document.

 

register example.bmp

 

The Entity bean: user.java

user.bmp

 

  • Entity annotation      indicates that the user class is an entity
  • Name annotation indicates      that the user class is a JBoss seam component named “user”
  • Scope annotation indicates      that the context associated with the class
  • NotNull annotation is part      of the Hibernate validator framework that can be used in persistent layer      and JSF layer

 

The Action class: RegisterAction.java

 

action.bmp

  • Stateless annotation      indicates that the Registration class is a stateless session bean
  • In annotation indicates      that  user object will be injected      by Seam container
  • PersistenceContext annotation      indicates that the EntityManager object em will be injected.
  • The register method simply      uses entity manager to persist the user object into database.

 

 

 

 

 

 

The View: Register.xhtml

view.bmp

  • S:validateAll tag tell      Seam to validate all input fields against Hibernate validator
  • JSF facelet EL      “#user.username” binds the username input field to the username attribute      of the “user” Seam component.
  • The commandButton tag binds      the “register” button to the “register” method of “register” component.  When a user clicks on the register      button, the register method will be invoked.

The View: Registered.xhtml

 

registered.bmp

  • When the register method      is successfully executed, the system will then display the registered message.