[Muir] Seam 2 in practice

Seam

Pete Muir
JBoss, a Division of Red Hat

http://in.relation.to/Bloggers/Pete

pete.muir@jboss.org

Road Map

• What is Seam?
• Why should I care about atomic conversations?
• How do I quickly build an application with Seam?
• What tools are available?
• The future

Application Stack
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Where can I run my app?

WebSphere Web Logic

Tomcat Glassﬁsh

JBoss Enterprise
JBoss Application Server
Application Platform

JBoss SOA Platform

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Seam is contextual
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• Stateful
• store objects for as long as you *#+$
need them

• Seam manages all interactions ,-)($.&#quot;/-)
with the context

• dependencies are injected and !$&&/-)
updated every time a component
is accessed
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Seam will store the
The uniﬁed component model component in the
conversation context
@Name(quot;discEditorquot;) @Scope(CONVERSATION)
public class DiscEditor {
Inject the
@In EntityManager entityManager; EntityManager

@In Session mailSession;

@In @Out Item disc; Inject a
JavaMail
@In(scope=SESSION) User user; session
Alias the item from the
// Use the components in some way context, and update the
;-)
context if the object
} changes
Specify the
context to inject
from 8

Why do I want an atomic conversation?

• Here’s a common scenario:
• A user has a task to complete which:
• spans multiple pages

• should be able to click cancel or back at any time, no changes made
until the user is ﬁnished

• should be able to do the same task in multiple windows

Review and conﬁrm
View a hotel Enter your booking
booking

What does Seam provide?
• A conversation scope
• shorter than the session, longer than a request

• demarcated by the application developer

• a conversation per window/tab

Application
Session Session
Conversation Conversation
Request Request


• A conversation scoped persistence context keeps entities
attached for the entirety of the user’s task
• guarantees object equality

• allows lazy loading

• An atomic conversation needs to only ﬂush changes at
particular points
• Only ﬂush the persistence context when explicitly instructed to

• An atomic conversation needs to only ﬂush changes at
particular points
• Need to use a manual ﬂush mode from Hibernate

@Begin(flushMode=MANUAL)
public void editDisc() {
// Load the item to edit
}

@End
public void saveDisc() {
entityManager.flush();
}

How do I manage the system transaction then?
• Seam manages the system transaction for you
• A read-write transaction

• A read only transaction for rendering the page (slightly better
than Open Session in View)

CONVERSATION
EVENT EVENT
APPLY INVOKE RENDER
RESTORE PROCESS UPDATE
REQUEST APPLICATION RESPONSE
VIEW VALIDATIONS MODEL
VALUES

PERSISTENCE CONTEXT
FLUSH

SYSTEM TRANSACTION

Application Framework
• UI orientated controller components Can deﬁne in XML or
Java for custom
• EntityHome for CRUD behaviour

<fwk:entity-home entity-class=quot;com.acme.Discquot; name=quot;discHomequot;/>

<s:decorate template=quot;/edit.xhtmlquot;>
<h:inputText value=quot;#{disc.name}quot; required=quot;truequot; />
</s:decorate>
<h:commandButton action=quot;#{discHome.update}quot; value=quot;Savequot; />
<h:commandButton action=quot;#{discHome.remove}quot; value=quot;Deletequot; />

Seam provides JSF Bind directly to
controls for easy the entities, no
decoration of ﬁelds need for DTOs

• EntityQuery for search
<fwk:entity-query name=quot;discsquot; ejbql=quot;select d from Disc dquot; order=quot;d.namequot;
max-results=quot;5quot;>
<fwk:restrictions>
<value>lower(d.name) like concat(#{exampleDisc.name}, '%'))</value>
</fwk:restrictions>
</fwk:entity-query> Basic queries can be
speciﬁed in XML

<component name=quot;exampleDiscquot; class=quot;com.acme.Artistquot; scope=quot;sessionquot; />

A prototype, used
to bind query
parameters
between UI and
query

• EntityQuery for search
Search criteria
<h:form>
Filter by name:
<h:inputText value=quot;#{exampleDisc.name}quot;>
<a:support reRender=quot;artistsquot; event=quot;onkeyupquot; />
</h:inputText>
</h:form>
Output the results
<h:table value=quot;#{discs.dataModel}quot; var=quot;dquot; id=quot;discsquot;>
<h:column>
<s:link action=quot;discquot; value=quot;#{disc.name}quot;>
<f:param name=quot;discIdquot; value=quot;#{disc.id}quot; />

</s:link>
</h:column>
</h:table>

<h:inputText value=quot;#{disc.name}quot; required=quot;truequot;>
<s:validate />
</h:inputText>

Validation
• Need to report validation errors back to the user on the correct
ﬁeld
• BUT normally need to enforce same constraints at the
persistence layer and the database

@Entity public class Item {

@Id @GeneratedValue Long id;

@Length(min=3, max=1000, message=quot;Must be between 3 & 1000 charsquot;)
String description;
}

Tooling

• seam-gen - command line tool for generating skeleton
project and reverse engineering a database schema
using Seam Application Framework
• JBoss Developer Studio - Eclipse based IDE
• For $99 you get a full installer + JBoss EAP
• Based on the freely available JBoss Tools Eclipse plugins

Flex as a view layer

• A community effort
• Uses Granite Data Services or Blaze Data Services
• Check out a couple of demos at

http://www.rationaldeveloper.com

JSF 2

• Easy Component Creation & Templating
• Standardizes Facelets

• No XML needed to create a component

• Built in Ajax support
• Many improvements to JSF
• lifecycle (performance!)

• error handling

• navigation

What else?

• Seam 2.1 release candidate in the next week or two
• Friendly URLs

• Identity Management

• ACL style permissions

• Wicket support

• Excel reporting module

• Support for JAX-RS (REST)

Q&A

http://in.relation.to/Bloggers/Pete

http://www.seamframework.org

[Muir] Seam 2 in practice

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