Moving to Java EE 6 and CDI and away from the clutter

Move to Java EE 6 and CDI...

...and away from the clutter

Dan Allen
Principal Software Engineer
JBoss by Red Hat

Agenda

● Java EE 6: All platform, no clutter
● Java EE's new wiring: JSR-299
● JSR-299 principles
● CDI programming model tour
● CDI extensions
● Weld
● Seam 3

2 Java EE and CDI | Dan Allen

Why reevaluate?


Landscaping or a roof garden?
Java EE
Framework X


What is Java EE?

● Standard platform comprised of
managed components & services

● Business logic as components
1. Less code
2. Higher signal-to-noise ratio
3. Powerful mechanisms for free
4. Portable knowledge


The Java EE we always wanted

● No-interface EJBs
● Embeddable EJB container
● Simplified packaging
● EJBs in a WAR
● POJOs, finally! Java EE
● Annotations + partial descriptors 6
● No more XML-hell XML
● Web profile
● GTD in Java EE


Web profile stack (read as: all you need)

● Persistence ● Presentation
● JPA 2.0 ● JSF 2.0
● JTA 1.1 ● Servlet 3.0
● Component model ● JBoss AS extras
● EJB 3.1 (lite) ● JMS 1.1
● CDI 1.0 ● JAX-RS 1.1
● Bean Validation 1.0


Technology terminology

● JSR-299 (CDI)
● Contexts & Dependency Injection for the
Java EE Platform
● Weld
● JSR-299 Reference Implementation & TCK
● Extended CDI support (Servlets, Java SE)
● Portable CDI enhancements and utilities
● Seam 3
● Portable extensions for Java EE
● Portable integrations with non-Java EE technologies


Stated goal of JSR-299

Web tier Transactional tier
(JSF) (EJB)


What CDI provides

● Services for Java EE components
● Lifecycle management of stateful beans bound to
well-defined contexts (including conversation context)
● A type-safe approach to dependency injection
● Interaction via an event notification facility
● Reduced coupling between interceptors and beans
● Decorators, which intercept specific bean instances
● Unified EL integration (bean names)
● SPI for developing extensions for the Java EE platform
● Java EE architecture  flexible, portable, extensible


CDI: The big picture

● Fill in
● Catalyze
● Evolve


Whoa, why dependency injection?

● Weakest aspect of Java EE 5
● Closed set of injectable resources
● @EJB
● @PersistenceContext, @PersistenceUnit
● @Resource (e.g., DataSource, UserTransaction)
● Name-based injection is fragile
● Lacked rules


Leverage and extend Java’s type system

@Annotation <TypeParam>

This information is pretty useful!

Type


JSR-299 theme

@Produces @WishList
Loose coupling... List<Product> getWishList()

Event<Order>
@InterceptorBinding
@Inject @UserDatabase EntityManager
@Observes
@Qualifier ...with strong typing


Loose coupling

●
Decouple server and client
● Contract based on well-defined types and “qualifiers”
●
Decouple lifecycle of collaborating components
● Stateful components interact like services
●
Decouple orthogonal concerns (AOP)
● Interceptors & decorators
●
Decouple message producer from consumer
● Events


Strong typing

● Type-based injection
● Eliminate reliance on string-based names
● Refactor friendly
● Compiler can detect typing errors
● No special authoring tools required
● Casting mostly eliminated
● Semantic code errors detected at application startup
● Enables strong tooling
● Preemptively detect errors
● Navigate relationships

Strong typing = strong tooling
CDI tools available in JBoss Tools 3.2 - http://jboss.org/tools


Who's bean is it anyway?

● Everyone throwing around this term “bean”
● JSF
● EJB
● Seam
● Spring
● Guice
● Web Beans
● Need a “unified bean definition”


Managed bean specification

● Common bean definition
● Instances managed by Managed
the container Beans

● Common services
● Lifecycle callbacks
● Resource injections
● Interceptors JSF EJB CDI JAX-RS

● Foundation spec

How managed beans evolved: http://www.infoq.com/news/2009/11/weld10

CDI bean ingredients

● Set of bean types
DI contract
● Set of qualifiers
● Scope
● Bean EL name (optional)
● Set of interceptor bindings
● Alternative classification
● Bean implementation class

Auto-discovered!


Welcome to CDI, managed bean!

public class Welcome {
public String buildPhrase(String city) {
return "Welcome to " + city + "!";
}
}


Welcome to CDI, EJB 3.1 session bean!

@Stateless public class Welcome {
}
}


When is a bean recognized?

● Bean archive (WAR) ● Bean archive (JAR)

beans.xml can be empty!


Injection 101

public class Greeter {
@Inject Welcome w;

public void welcome() {
System.out.println(
w.buildPhrase("New York"));
}
}


Where can it be injected?

● Field
● Method parameter
● Constructor*
● Initializer
● Producer
● Observer


What can be injected?

Managed bean

Object returned by producer

EJB session bean (local or remote)

Java EE resource (DataSource, JMS destination, etc)

JTA UserTransaction

Persistence unit or context

Security principle

Bean Validation factory

Web service reference

Additional resources introduced through SPI


The bean vs “the other implementation”

public class Welcome {
}
}

public class TranslatingWelcome extends Welcome {

@Inject GoogleTranslator translator;

return translator.translate(
"Welcome to " + city + "!");
}
}


Quiz: Which implementation gets injected?

private Welcome welcome;

@Inject
void init(Welcome welcome) {
this.welcome = welcome;
}

...
}

It's ambiguous!


Working out an ambiguous resolution

● Qualifier
● Alternative
● Veto (or hide)


qualifier

n. an annotation used to resolve an API
implementation variant at an injection point


Defining a qualifier

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

@interface = annotation
@interface = annotation


Qualifying an implementation

@Translating


}
}

● Qualifiers:
● makes type more specific
● assign semantic meaning


Qualifier as a “binding type”


Explicitly request qualified interface

private Welcome welcome; No reference to implementation class!
No reference to implementation class!
@Inject
void init(@Translating Welcome welcome) {
}

public void welcomeVisitors() {
System.out.println(
welcome.buildPhrase("New York"));
}
}


Alternative bean

● Swap replacement implementation per deployment
● Replaces bean and its producers
● Activated in /META-INF/beans.xml
● Disabled by default

In order words, a replacement


Defining an alternative

@Alternative


}
}


Substituting the alternative using beans.xml

<beans>
<alternatives>
<class>com.acme.TranslatingWelcome</class>
</alternatives>
</beans>


Assigning a bean (EL) name

@Named("greeter")
private Welcome welcome;

@Inject
}

System.out.println(
}
}


Assigning a bean (EL) name by convention

@Named
private Welcome welcome; Bean name is decapitalized
Bean name is decapitalized
simple class name
simple class name
@Inject
}

System.out.println(
}
}


Welcome to CDI, JSF!

● Use the bean directly in the JSF view
<h:form>
<h:commandButton value="Welcome visitors"
action="#{greeter.welcomeVisitors}"/>
</h:form>


JSF
managed
beans

CDI


Stashing the bean in a context
Bean stored for duration of request
Bean stored for duration of request
@Named
@RequestScoped
@Inject private Welcome w;
private String city;

public String getCity() { return city; }

public void setCity(String city) {
this.city = city;
}

System.out.println(w.buildPhrase(city));
}
}


Collapsing layers with state management

● Now it’s possible for bean to hold state
<h:form>
<h:inputText value="#{greeter.city}"/>
<h:commandButton value="Welcome visitors"
action="#{greeter.welcomeVisitors}"/>
</h:form>

New York

Prints:
Welcome to New York!


Mission accomplished: We have a deal!

Web tier Business tier
(JSF) (managed bean)


Scope types and contexts

● @Dependent – Default scope
● Bound to lifecycle of bean holding reference
● @ApplicationScoped
● @RequestScoped Servlet scopes
● @SessionScoped
● @ConversationScoped – JSF scope
● Request ≤ Conversation ≪ Session
● Custom scopes
● Define scope type annotation (e.g., @FlashScoped)
● Implement the context API in an extension

Scope transparency

● Scopes not visible to client (no coupling)
● Scoped beans are proxied for thread safety


producer method

n. a method whose return value produces
an injectable object


Producer method examples

@Produces @RequestScoped
public FacesContext getFacesContext() { From non-bean
From non-bean
return FacesContext.getInstance();
}

@Produces
public PaymentProcessor getPaymentProcessor(
@Synchronous PaymentProcessor sync,
Runtime selection
Runtime selection
@Asynchronous PaymentProcessor async) {
return isSynchronous() ? sync : async;
}

@Produces @SessionScoped @WishList Dynamic result set
Dynamic result set
public List<Product> getWishList() {
return em.createQuery("...").getResultList();
}


Injecting producer return values

@Inject FacesContext ctx;

@Inject PaymentProcessor pp;

@Inject @WishList List<Product> wishlist;

Origin of product is hidden at injection point


Bridging Java EE resources to CDI

public class UserEntityManagerProducer {
@Produces @InventoryRepository
@PersistenceContext(unitName = "inventory")
private EntityManager inventory;
}
Producer fields can promote
Producer fields can promote
Java EE resources as beans
Java EE resources as beans
public class PricesTopicProducer {
@Produces @Prices
@Resource(name = "java:global/env/jms/Prices")
private Topic pricesTopic;
}


Injecting resources in type-safe way

public class UserManager {
@Inject @InventoryRepository
EntityManager inventory;
...
}
Eliminates string-based
Eliminates string-based
names at injection points
names at injection points
public class StockDisplay {
@Inject @Prices
Topic pricesTopic;
...
}


Java EE 6: Simple, clean and integrated

@Stateless
@Path("/product")
public class ProductResourceHandler {
@Inject @InventoryDatabase EntityManager em;

@GET @Path("/{id:[1-9][0-9]+}")
@Produces("application/xml")
public Product getProduct(@PathParam("id")
Long id) {
return em.find(Product.class, id);
}
}


Rethinking interceptors

@Interceptors(
SecurityInterceptor.class,
TransactionInterceptor.class,
LoggingInterceptor.class
)
@Stateful public class BusinessComponent {
...
}

Um, what's the point?


Define an interceptor binding type

@InterceptorBinding
@Retention(RUNTIME)
@Target({TYPE, METHOD})
public @interface Secure {}


Mark the interceptor implementation

@Secure
@Interceptor
public class SecurityInterceptor {

@AroundInvoke
public Object aroundInvoke(InvocationContext ctx)
throws Exception {
// enforce security...
ctx.proceed();
}

}


Interceptor wiring with proper semantics

@Secure
public class AccountManager {

public boolean transfer(Account a, Account b) {
...
}

}


Enabling interceptors using beans.xml

<beans>
<interceptors>
<class>com.acme.SecurityInterceptor</class>
<class>com.acme.TransactionInterceptor</class>
</interceptors>
</beans>
Interceptors applied in order listed
Interceptors applied in order listed


Annotation jam!

@Secure
@Transactional
@RequestScoped
@Named

...
}

}


stereotype

n. an annotation used to group common
architectural patterns (recurring roles)


Define a stereotype to bundle annotations

@Secure
@Transactional
@RequestScoped
@Named
@Stereotype
@Retention(RUNTIME)
@Target(TYPE)
public @interface BusinessComponent {}


Using a stereotype

@BusinessComponent

...
}

}


Portable extensions

● Auto-discovered
Se
rvic
● Integrate with the container by: eP
rov
ide
r Inte
rfac
● Providing beans, interceptors or decorators e (S
PI )
● Injecting dependencies into its own objects
● Contributing a scope and context implementation
● Augmenting or overriding annotation metadata
● Observe container lifecycle events
● Before/after bean discovery
● After deployment validation
● Processing bean, producer, observer, or injection target


Weld: The axis of CDI

Implement Validate
(RI) (TCK)

Reach Improve
(Servlet, SE) (Extensions)


JSR-299 RI & TCK

● Reference Implementation (RI)
● Technology Compatibility Kit (TCK)
● Developer-oriented reference guide
Other implementations:
●
● Apache OpenWebBeans
●
● Resin CanDI


Weld “X”

● A library of Generally Useful Stuff™
● Enhancements to CDI programming model
● Bean discovery control
● Injectable logger and resource loader
● EL evaluator and more...
● Utilities for framework & extension writers
● Annotation metadata utilties
● JavaBean inspectors
● BeanManager locator and more...


Seam’s mission statement

To provide a fully integrated development
platform for building rich Internet applications
based upon the Java EE environment.


Seam’s new modular ecosystem


Portable modules

● Module per domain or integration
● Independently...
● lead
● versioned
● released
● Per-module structure
● Based on CDI
● API & implementation
● Reference documentation & examples


Stack releases


What's on the menu so far?

● Drools ● JavaScript remoting
● jBPM ● Security
● JMS ● Servlet
● Faces ● Wicket
● International ● XML configuration
● Persistence ● Exception handling
...and more
 http://github.com/seam


XML-based configuration

<beans ...
xmlns:app="java:urn:com.acme">
<app:TranslatingWelcome>
<app:Translating/>
<app:defaultLocale>en-US</app:defaultLocale>
</app:TranslatingWelcome>
</beans>

● Define, specialize or override beans
● Add annotations (qualifiers, interceptor bindings, ...)
● Assign initial property values


Arquillian: Container-oriented testing for Java EE
@RunWith(Arquillian.class)
public class GreeterTestCase {

@Deployment
public static Archive<?> createDeployment() {
return ShrinkWrap.create(JavaArchive.class)
.addClasses(Greeter.class, GreeterBean.class);
}

@EJB private Greeter greeter;

@Test
public void shouldBeAbleToInvokeEJB() throws Exception {
assertEquals("Hello, Earthlings", greeter.greet("Earthlings"));
}
} http://jboss.org/arquillian


Summary

● Java EE 6 is leaner and more productive
● JSR-299 (CDI) provides a set of services for Java EE
● Bridges JSF and EJB
● Offers loose coupling with strong typing
● Provides a type-based event bus
● Catalyzed change in Java EE 6
● Introduced SPI for third-party integration with Java EE
● Weld: JSR-299 reference implementation & add-ons
● Seam 3: Portable extensions for Java EE


How do I get started?

● Download a Java EE 6 container
● JBoss AS 6 ● GlassFish V3
http://jboss.org/jbossas http://glassfish.org
● Generate a Java EE project using a Maven archetype
● http://tinyurl.com/goweld
● Read the Weld reference guide
● http://tinyurl.com/weld-reference-101
● Browse the CDI API docs
● http://docs.jboss.org/cdi/api/latest/
● Check out the Seam 3 project
● http://seamframework.org/Seam3

Say goodbye to the clutter !

Dan Allen
Principal Software Engineer
JBoss by Red Hat

http://seamframework.org/Weld
http://seamframework.org/Seam3

Moving to Java EE 6 and CDI and away from the clutter

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