SEAM
A GLASSFISH PERSPECTIVE
DAN ALLEN
JBOSS, A DIVISION OF RED HAT

SEAM BRINGS JAVA EE TOGETHER
JSF EJB 3

SEAM'S MISSION
“To provide a fully integrated development platform
for building rich Internet applications based upon the
Java EE environment.” - Gavin King
http://in.relation.to/Bloggers/Seam3

WHAT SEAM PROVIDES
“Glue”
– Contextual component model
– Dependency injection framework
– Enhanced EL
Simplify Java EE trouble spots
Manage Java Persistence correctly
Modules to integrate third-party libraries
Rapid development environment
– Project generator, CRUD framework, hot deploy

SEAM TODAY
JavaServer Faces (JSF) Java Authentication and
Authorization Service (JAAS)
Facelets
Hibernate search
Java Persistence API (JPA)
Drools
Enterprise JavaBeans 3 (EJB 3)
JavaScript / Ajax
Java Transaction API (JTA)
Quartz
JAX-RS (RESTeasy)
Wicket
jBPM
GWT
JavaMail
Spring framework
iText (PDF)
JBoss Cache
JExcelApi (Excel)
...and more
YARFRAW (RSS)

SEAM EJB COMPONENT
EJB Local Reference in web.xml
<ejb-local-ref>
<ejb-ref-name>vehiclesee/VehicleTradeBean/local</ejb-ref-name>
<ejb-ref-type>Session</ejb-ref-type>
<local>org.example.vehicles.action.VehicleTrade</local>
</ejb-local-ref>
EJB Local Interface and Seam SFSB component
@Local @Stateful
public interface VehicleTrade { @Name(\"vehicleTrade\")
void trade(); public class VehicleTradeBean
void remove(); implements VehicleTrade {
} public void trade() { ... }
@Remove public void remove() {}
}
How does Seam make the connection?

RESOLVING AN EJB IN SEAM
A shared concern
First option: @JndiName
Second option: Resolve JNDI from pattern
– #{ejbName}
● Value of name attribute on @Stateful/@Stateless
● Unqualified class name of component
● Value of <ejb-name> in ejb-jar.xml or web.xml
– Plug into Seam's jndiPattern
SFSB reference stored in Seam context
– Default is conversation context

INVOKING AN EJB FROM JSF
It's not a crime!
<h:form> @Stateful
... @Name(\"vehicleTrade\")
public class VehicleTradeBean
<h:commandButton value=\"Trade\"
implements VehicleTrade
action=\"#{vehicleTrade.trade}\"/> {
</h:form>
public void trade() { ... }
@Remove public void remove() {}
}
CLIENT SERVER

JAVA PERSISTENCE

PERSISTENCE MANAGER
JPA EntityManager or Hibernate Session
Manages object representations of
database records
Key services
– First-level cache
– Transparent database reads/writes
Aligns well with use case
– Seam terms this a “conversation”

CONVERSATION = UNIT OF WORK
The task at hand
Often involves more than one request
Requires state management

EXTENDING THE PERSISTENCE CONTEXT
Not expensive or dangerous!
– “Just a HashMap”
Challenging to do in Java EE
– No good place to store it
– Complex propagation rules
We turn over this task to Seam

TWO STYLES OF MANAGEMENT
Seam (bi)jection Standard Java EE injection
@In @PersistenceContext
EntityManager entityManager; EntityManager entityManager;

EXTENDING THE TRANSACTION
Simulate a long transaction
– Transcends many database/system transactions
Manual flushing of persistence context
– You control when write occurs
– Rollback without involving database
– Persistence context can be read-only
– Only Hibernate provides this extension
Need to replace JPA provider in GlassFish
– Seam provides access to Hibernate extensions
– Seam works agreeably with any JPA provider

APPLICATION TRANSACTION
Conversation (flushMode = MANUAL)
Request Response Request Response
...
Transaction Transaction
load flush

EMBEDDED JAVA EE TESTING
SeamTest
– Based on TestNG
Test application “as is”
– Full JSF life cycle
– JTA, EJB 3, EL
Currently uses Embedded JBoss
– Has baggage
Look forward to EJB 3.1

SEAM
A GLASSFISH PERSPECTIVE
DAN ALLEN
JBOSS, A DIVISION OF RED HAT