Seam

Introduction

Seam manages components, that means it manages the complete lifecycle and scope of the components (inversion of control principle), named as context of a component. Thereto it injects dependencies to the components (dependency injection).

Most Seam application use session beans as JSF action listeners.

Seam lets you use a JSF EL expression inside EJB-QL. Under the covers, this results in an ordinary JPA setParameter() call on the standard JPA Query object.

Seam integrates Hibernate Validator and lets you use it for data validation (even if you are not using Hibernate for persistence).

Installation and Configuration

• download jboss-seam-2.0.2.SP1.zip and extract to <ECLIPSE_WORKSPACE>
• add jboss.home to <SEAM_DIR>\build.properties

Annotations

Seam defines own annotations and uses some other annotations.

org.hibernate.validator.Length

@org.hibernate.validator.Length
<attribute declaration>

for length validation

org.hibernate.validator.NotNull

for validation

org.jboss.seam.annotations.In

@org.jboss.seam.annotations.In
<attribute_declaration>

The attribute is injected by Seam.

org.jboss.seam.annotations.Logger

@org.jboss.seam.annotations.Logger

The annotation is used to inject the component's Log instance. The logger has a specialised syntax e.g.

log.info("creating component '#0' on #1", name(), date());
log.info("#{<object>.<attribute>}");

org.jboss.seam.annotations.Name

@org.jboss.seam.annotations.Name("<Name>")
<class_declaration>

specifies the name of the Seam component. This name must be unique within the Seam application. When JSF asks Seam to resolve a context variable with a name that is the same as a Seam component name, and the context variable is currently undefined (null), Seam will instantiate that component, and bind the new instance to the context variable.

org.jboss.seam.annotations.Scope

org.jboss.seam.annotations.Scope(org.jboss.seam.ScopeType.<SCOPE_TYPE>)
<class_declaration>

specifies the scope of a seam component. Types are:

EVENT	the component lives only for one method call

Standard components

Identiy

@In
Identity idendity;

is a standard component of the Seam security model und lives as long as the session.

Applications

• s. Installation