Introduction to CDI and DI in Java EE 6

Productive,
LEARNING CDI Simple,
Modern

Ray Ploski
Director, Developer Programs & Strategy
JBoss, by Red Hat, Inc.

AGENDA
 Background
 Concepts
 Status & Roadmap

DEVELOPER PRODUCTIVITY
- WHAT IF?

Faster Start-Up Times 80% Less Configuration

50% Less Code Open eco-system

25% Less Classes
Vendor Agnostic

Rapid Application Tooling
Easier Integration Testing
* Based on a Sample POJO/JPA/REST Based Application

J2EE
#fail
#fail

EJB
#fail

EJB 2.X DEPLOYMENT DESCRIPTOR


<enterprise-beans>
<session>
<display-name>BankSB</display-name>
<ejb-name>BankBean</ejb-name>
<local-home>com.advocacy.legacy.ejb.BankLocalHome</local-home>
<local>com.advocacy.legacy.ejb.BankLocal</local>
<ejb-class>com.advocacy.legacy.ejb.BankBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Container</transaction-type>
</session>
</enterprise-beans>
<assembly-descriptor>
<container-transaction>
<method>
<ejb-name>BankSB</ejb-name>
<method-name>*</method-name>
</container-transaction>
</assembly-descriptor>

JAVA EE 5
 Annotation Enhancements
 Resource injection in JEE5
 @EJB, @Resource, @PersistenceContext,
 @PersistenceUnit

 Into Container Components:
 Servlets, JSF backing beans and other EJBs

 Progress but still Problems
 No POJOs
 Cannot inject DAOs or helper classes that were not written as
EJBs
 Hard to integrate anything but strictly business components

JAVA EE 6

The EE 6 web profile removes most of
the “cruft” that has developed over
the years
 mainly totally useless stuff like web
services, EJB 2 entity beans etc.
 some useful stuff (e.g. JMS) is
missing, but vendors can include it

EJB 3.1 SESSION BEAN

OPTIONAL!

JAVA EE 6 DEPLOYMENT
DESCRIPTOR

EJB 3.1 CLIENT VIEW
@EJB BankLocal bank;

public void makeDeposit()
{
bank.deposit(2500.00, new Account(12345));
}

HOW DID THEY DO THAT?
Configuration by exception with sensible
defaults
 Security permissions defaults to UNCHECKED
 Transaction type defaults to CONTAINER
 Transaction attribute defaults to REQUIRED
Use Annotations
 To choose explicitly (recommended)
 To override defaults
Deployment descriptor is no longer required
 But can override above configurations

EASE OF USE IMPROVEMENTS

 Optional Local Interface
 Simplified Packaging
 EJB-Lite
 Portable JNDI Naming
 Simple Component Testing

JAVA EE 6

 EJB 3.1 - asynch, no-interface views, embeddable
 JPA 2.0 - typesafe criteria API, many more O/R
mapping options
 JSF 2.0 - Ajax, easy component
creation, bookmarkable URLs
 Bean Validation 1.0 - annotation-based validation
API
 Servlet 3.0 - async support, better support for
frameworks
 Standard global JNDI names
 Managed Beans

MANAGED BEANS

Container-managed POJOs with
minimal requirements
support a set of basic services
 resource injection
 lifecycle callbacks
 interceptors

MANAGED BEANS

 the foundation for all other component
types in the platform
core services centralized under Managed
Beans
 Other specifications will add support for
additional services
remoting
instance pooling
web services

AGENDA
 Background

 Concepts
 Status & Roadmap

Loose Coupling

STRONG TYPING

DEPENDENCY INJECTION
IN TWO PARTS
DI (@Inject) CDI
JSR 330 JSR 299
javax.inject javax.enterprise.context

@Inject Alternatives
@Named Producers
@Singleton Scopes
@Qualifier Stereotypes
@Scope Decorators
Extensions

SIMPLE EXAMPLE

public class Hello { Any Managed Bean
public String sayHello(String name) {
can use these
return "hello" + name;
} services
}

@Stateless So can EJBs
public class Hello {
}
}

SIMPLE EXAMPLE

@Inject defines an
public class Printer { injection point.
@Inject Hello hello;
@Default qualifier is
assumed
public void printHello() {
System.out.println( hello.sayHello("world") );
}
}

CONSTRUCTOR INJECTION

public class Printer { Mark the constructor to be
private Hello hello; called by the container
@Inject
@Inject
public Printer(Hello hello) { this.hello=hello; }

System.out.println( hello.sayHello("world") );
}
}

Constructors are injected by
default; @Default is the
default qualifier

MANAGED BEAN NAMES

By default not
@Named("hello")
available through EL.
}
} If no name is specified, then a
default name is used. Both
these Managed Beans have
@Named the same name
}
}

JSF PAGE

<h:commandButton value=“Say Hello”
action=“#{hello.sayHello}”/>

Calling an action on a
bean through EL

WHAT MAKES CDI UNIQUE?
Standard
Type Safe
Extensible

DEFINING THE QUALIFIER

@Qualifier
@Retention (RUNTIME)
@Target({FIELD,TYPE,METHOD,PARAMETER})
public @interface NumberOfDigits {

Digits value();
}
Creating a qualifer is
really easy!
public enum Digits {

TWO, EIGHT, TEN, THIRTEEN
}

Example Credit: Antonio Goncalves

DEFINING THE BEANS
@NumberOfDigits (Digits.EIGHT)
public class IssnGenerator {

public String generateNumber() { We specify the
return “8-” + nextNumber(); @NumberOfDigits
} qualifier. If no qualifer is
} specified on a
bean, @Default is
@NumberOfDigits (Digits.THIRTEEN) assumed
public class IsbnGenerator{

public String generateNumber() {
return “13-84356” + nextNumber();
}
}


QUALIFIED INJECTION OF
RESOURCES
@Path(”/items") @ManagedBean
public class ItemRestEndpoint {
Here we inject the
@Inject @NumberOfDigits(Digits.EIGHT) qualified
private NumberGenerator numGen;
beans, and require
…
}
and profit

@WebServlet(urlPatterns=”/itemServlet")
public class ItemServlet {

@Inject @NumberOfDigits(Digits.THIRTEEN)
private NumberGenerator numGen;
…
}


ALTERNATIVES

An alternative bean is one which must be
specifically enabled for a particular
deployment
It replaces the managed or session bean for
which it is an alternative
May also completely replace it
 all producers and observers defined on original
bean are disabled for this deployment)
Alternatives enabled in XML deployment
descriptor

DEFINING AN ALTERNATIVE

@Alternative Same API, different
@ThirteenDigits @EightDigits implementation
public class MockGenerator implements
NumberGenerator {

public String generateNumber() {
return ”MOCK- " + nextNumber();
}

}

ENABLING AN ALTERNATIVE

<beans>
<alternatives>
<class>com.acme.MockGenerator</class>
<stereotype>com.acme.numbers.mock</stereotype>
</alternatives>
</beans>

Can also define a sterotype as
an alternatives. Any
stereotyped beans will be an
alternative

STEREOT YPES

 We have common architectural
“patterns” in our application, with
recurring roles
Capture the roles using stereotypes
 Stereotypes may declare other
stereotypes
 (Built-In example @Model)

STEREOT YPES

A stereotype encapsulates any
combination of:
a default scope, and
a set of interceptor bindings.
A stereotype may also specify that:
all beans with the stereotype have defaulted
bean EL names
all beans with the stereotype are alternatives

CREATING A STEREOT YPE

@RequestScoped Scope
@Named
@Alternative
@Stereotype Has a defaulted name
@Retention(RUNTIME)
@Target(TYPE)
public @interface MyAlternativeAction{}
All stereotyped beans
become alternatives

USING A STEREOT YPE

@MyAlternativeAction
return "hi " + name;
}
}

SCOPES AND CONTEXTS

Built-in scopes:
 Any servlet -
@ApplicationScoped, @RequestScoped, @Sess
ionScoped
 JSF requests - @ConversationScoped
 Dependent scope (Default): @Dependent
Custom scopes
 A scope type is an annotation, can write your own
context implementation and scope type annotation

SCOPES

@SessionScoped
public class Login { Session scoped
private User user;
public void login() {
user = ...;
}
public User getUser() { return user; }
}

SCOPES

public class Printer {
No coupling between
@Inject Hello hello; scope and use of
@Inject Login login; implementation
System.out.println(
hello.sayHello( login.getUser().getName() ) );
}
}

PRODUCER METHODS

Producer methods allow control over the
production of a bean where:
the objects to be injected are not managed
instances
the concrete type of the objects to be injected
may vary at runtime
the objects require some custom initialization
that is not performed by the bean constructor

47
47 Pete Muir

PRODUCER METHODS

@SessionScoped
public class Login {
private User user;
user = ...;
}

@Produces
User getUser() { return user; }
}

PRODUCER METHODS

public class Printer {
@Inject Hello hello;
@Inject User user; Much better, no
public void hello() { dependency on
System.out.println( Login!
hello.sayHello( user.getName() ) );
}
}

PRODUCER FIELDS

Simpler alternative to Producer methods

Similar to
@SessionScoped outjection in
public class Login {
Seam
@Produces @LoggedIn @RequestScoped
private User user;

user = ...;
}
}

JAVA EE RESOURCES

public class PricesTopic {
@Produces @Prices
@Resource(name="java:global/env/jms/Prices")
Topic pricesTopic;
}

public class UserDatabasePersistenceContext {
@Produces @UserDatabase
@PersistenceContext
EntityManager userDatabase;
}

EVENTS

Event producers raise events that are then
delivered to event observers by the Context
manager.
 not only are event producers decoupled from
observers; observers are completely decoupled from
producers
 observers can specify a combination of "selectors" to
narrow the set of event notifications they will receive
 observers can be notified immediately, or can specify
that delivery of the event should be delayed until the
end of the current transaction

Inject an instance of Event. Additional
EVENTS qulaifiers can be specified to narrow the
event consumers called. API type
specified as a parameter on Event


@Inject @Any Event<Greeting> greeting;

public void sayHello(String name) {
greeting.fire( new Greeting("hello " + name) );
}

}

“Fire” an event, the
producer will be notified

53
Pete Muir

EVENTS

Observer methods, take the API
public class Printer { type and additional qualifiers
void onGreeting(@Observes Greeting greeting,
@Default User user) {
System.out.println(user + “ says “ + greeting);
}

}
Additional parameters can
be specified and will be
injected by the container

CDI - EXTENSIBLE BY DESIGN
Many community projects of extensions:
 Seam 3, CODI, Cambridge Technology Partners

 Multiple projects merging to deliver a vendor -
neutral common platform for extensions named
DeltaSpike .
 Hosted on Apache. Works on Java EE 6 servers

+ + CDISource DeltaSpike

SEAM 3 MODULES

• Solder • Mail DeltaSpike
• Config • Validation
• Social • Wicket
• JMS • Catch
• JCR JBoss
• Remoting Developer
• Security
• REST Framework
• I18N Drools SwitchYard
• Faces
jBPM Errai
• Spring
TBD Ecetera

SEAM 3 SPRING MODULE

 Seam3 - a library of CDI extensions

 Similar functionality to the Seam 2 Spring
integration
 With CDI specific undertones

 Will merge into Apache DeltaSpike

SPRING-CDI BRIDGE

Use Java EE and Spring side by side

Spring Beans produced as Managed CDI
beans

Seam 3 Spring Module

INTEGRATING SPRING COMPONENTS INTO
CDI

Managed Managed
Bean Bean

Managed  Implemented as a
Bean
Standard CDI Extension

 Spring contexts and
• ApplicationContexts
Spring beans are installed
• Spring Beans as CDI beans
* Can be bootstrapped or external

 Implemented using the
resource producer pattern

THE SPRING DAO

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource”
destroy-method="close">
<property name="driverClassName" value="${jdbc.DriverClassName}"/>

<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>

<context:property-placeholder location="classpath:jdbc.properties"/>
<context:component-scan base-package="demo.spring"/>
<context:anntation-config/>

JSF / CDI BEAN

Here we do not
@Named @RequestScoped
want to know
public class BooksBean { about Spring

@Inject BooksJdbcDao booksDao;

public List<String> getTitles() {
return booksDao.listBookTitles();
}
}

@SPRINGCONTEXT
ANNOTATION
1.) Bootstrapped
By CDI Extension

SPRING BEAN PRODUCER
Apply the resource producer pattern for creating
Spring ApplicationContext CDI beans

SEAM3 SPRING MODULE DESIGN GOALS

 Minimize changes to existing code

 Non-intrusive approach

 Highly customizable

 Mirror similar capabilities

WHY?

 Reuse existing investments

 Integrate groups with various expertise

 Simplify integration of Spring and Java EE

 Ease migration of legacy Spring apps to Java
EE 6

SEAM 3 SPRING MODULE FEATURES

 Integrating Spring
components into CDI

 Accessing Spring
ApplicationContexts

 created by the extension
-or-
 access AC’s created by
Spring components (e.g.
web ApplicationContext)

 Accessing CDI beans

 exposing Spring beans as
CDI beans

I need one of
those widgets for
a marketing

T YPICAL DEVELOPER
meeting in an
hour.

NIGHTMARE

CARVE OUT A PROJECT
WORK IT INTO SHAPE

Demonstration of Forge
and Java EE Application

GETS YOU
STARTED
Handles details, gives you perspective QUICKLY
… and time
HANDLES
“GOTCHAS”

ADDS &
ACTIVATES
TECH
VIA
PLUGINS

TESTING JAVA EE USED TO BE
DIFFICULT

MANY STEPS REQUIRED FOR MODIFYING
CODE PRODUCTIVELY

 Reference Application
 https://github.com/jboss/ticket-monster
 7+ In-Depth Tutorials
 https://github.com/jboss/ticket-monster-
tutorial
 7+ Videos RESOURCES
 http://jboss.org/developer/videos
 55+ “Quickstarts”
 https://github.com/jbossas/quickstart
 6+ Articles and Whitepapers
 http://jboss.org/developer/articles.html
 http://www.howtojboss.com
 Social Campaign
 Google
 https://plus.google.com/b/114105440952945834
221/
 Twitter
 @TheJBossWay
 Facebook
 https://www.facebook.com/jboss

 Max Andersen
 “See Context & Dependency Injection from Java EE 6 in
Action”
 http://www.slideshare.net/maxandersen/see-context-
dependency-injection-from-java-ee-6-in-action

 Pete Muir REFERENCES
 “CDI in Action”
 Andrew Lee Rubinger
 “The Death of Slow”
 http://www.slideshare.net/ALRubinger/devoxx-2011-
jboss-as7-death-of-the-slow

Bert Ertman
 EJB 3.1
 http://www.slideshare.net/stephanj/ejb-31-by-bert-
ertman

 Antonio Goncalves
 “To inject or not to inject: CDI is the question”
 http://www.slideshare.net/agoncal/to -inject-or-not-to-inject-cdi-is-the-
question

ENTERPRISE
JAVA
APPLICATIONS
Results of lots of choice,
little guidance.

THE JBOSS WAY
Teaches developers how to easily adopt
technologies within JBoss EAP 6

• Webinar Series
• Reference Application “TicketMonster”
• 3 Reference Architectures
• 55+ Quickstarts
• 7+ In-Depth Tutorials
• 6+ Articles and Whitepapers
• 7+ Recorded Videos
• Social Campaign with HowTos
• Growing Set of Technical Blogs

JSF 2 HTML5 GWT
<h:form id="bookingForm"> <form name="reg" id="reg” public class Stockwatcher
<fieldset> <fieldset> implements EntryPoint {
<p:input id="checkInDate” <legend>Register a user: private VerticalPanel mainPanel
<h:inputText id="input” <div> private FlexTable stocksFlexTable
<f:convertDateTime type= <label for="email">Email: private HorizontalPanel addPanel
</h:inputText> <input type="email" private TextBox newSymbolText
name="email" id="email" private Button addStockButton
placeholder="Your Email”

More Choice
Struts SpringMVC Tapestry Wicket Flex Rails* …

CDI, EJB, Spring Beans

JPA, Hibernate

* Ruby on Rails on JBoss via TorqueBox

TICKET MONSTER
REFERENCE APPLICATION

SIMPLE ARCHITECTURE

Native Mobile
(Apache Cordova)

User Front-end (POH5)
Monitoring
Admin Front-end
Classic UI Mobile UI Dashboard
(JSF, Forge)
(GWT, Errai)

Forge
Business Layer (CDI, EJB, JAX-RS)
Scaffold

Persistence (JPA)

A MODERN SET OF TECHNOLOGIES

JBoss Developer Studio 5
OpenShift
- PaaS
Java EE 6 - Maven
- Jenkins
Web Framework Kit 2
JBoss EAP 6

Spring Support TorqueBox

Java EE 6

Red Hat Confidential - Do Not Distribute

Introduction to CDI and DI in Java EE 6

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