Java EE 6 introduced the new Context & Dependency Injection (CDI) specification and for the first time it is now possible and practical to build a full app just using the Java EE specification - all the pieces for an application is available out of the box on a Java EE 6 certified container. This talk will briefly introduce you to the concepts of CDI and then via code examples show how CDI and Java EE 6 have been used to implement key aspects of the application.

2. Context & Dependency Injection
from Java EE 6
in Action
Max Rydahl Andersen
Red Hat
http://about.me/maxandersen
14th April
Miracle Open World 2011

3. About Me
• Max Rydahl Andersen
• Lead of JBoss Tools & Developer Studio
• Committer on Hibernate Core, Seam & Weld
• Co-host of JBoss Community Asylum Podcast
• @maxandersen on Twitter
• http://about.me/maxandersen

4. Today’s goal is to answer ..

5. Today’s goal is to answer ..
Is JEE 6
awesome ?

6. Agenda
• What is new in Java EE 6 ?
• Quick Intro to CDI
• Deep-dive Example
• Solving real problems with EE 6

7. What is new in
Java EE 6 ?

8. What is new in Java EE 6 ?

9. What is new in Java EE 6 ?
• Forget everything bad you have seen or heard
about Java EE, because...
• ...it is highly simplified
• ...it’s actually usable now
• ...it Just Works!

10. Java EE 6: Goals
•Extensibility
•Allow more components to be standalone (EJB 3.1)
•Profiles
•Subsets of “full” EE platform
•Web Profile
•Pruning
•CMP, JAX-RPC, JAXR, JSR-88 are “pruned” in EE6
•Technology Improvements
8 Pete Muir

11. Java EE 6: Newcomers
•Managed Beans (part of JSR-316)
•Contexts and Dependency Injection - JSR-299
•Bean Validation - JSR-303
•JAX-RS (RESTful Web Services) - JSR-311
9 Pete Muir

12. Java EE 6: Notable Updates
•Servlet 3.0 •JSF 2
•Easier configuration •Ajax
•JPA 2.0 •Easy component creation
•Type-safe Criteria API •Bookmarkable URLs
•Extra mappings •Templating
•EJB 3.1
10 Pete Muir

13. Web Profile
•Persistence •Presentation
•JPA 2.0 •JSF 2.0
•JTA •Servlet 3.0
•Component model
•EJB 3.1 Lite
•Bean Validation
•CDI (JSR-299)
11 Pete Muir

14. Quick Intro to CDI

15. What is CDI ?
• “...unify the JSF managed bean component
model with the EJB component model,
resulting in a significantly simplified
programming model for web-based
applications.” - JSR-299/Gavin King
• “CDI simplifies and sanitizes the API for DI
and AOP like JPA did for ORM” - CDI
Tutorial/Rick Hightower

16. CDI Acronyms
• The Spec - Context & Dependency Injection
for JEE (CDI)
• The Reference Implementation - Weld
• Other implementations - CanDI (Resin),
Open WebBeans (Apache)

17. The Simplest CDI Bean
public class Welcome {
public String buildPhrase(String city) {
return "Hello from " + city + "!";
}
}

18. The Simplest Session Bean
@Stateless public class Welcome {
public String buildPhrase(String city) {
return "Hello from " + city + "!";
}
}

19. Simplest CDI Packaging

20. Simplest CDI Packaging
Can just be empty!

21. Dependency Injection
public class Greeter {
Welcome w;
public void welcome() {
System.out.println(w.buildPhrase("Billund"));
}
}

22. Dependency Injection
public class Greeter {
@Inject
Welcome w;
public void welcome() {
System.out.println(w.buildPhrase("Billund"));
}
}

23. Another Implementation
public class TranslatingWelcome extends
Welcome {
@Inject GoogleTranslator translator;
public String buildPhrase(String city) {
return translator.translate(
"Welcome to " + city + "!");
}
}

24. Quiz: What gets Injected ?
public class Greeter {
@Inject
Welcome w; // Welcome or TranslatingWelcome ?
public void welcome() {
System.out.println(w.buildPhrase("Billund"));
}
}

25. Qualifiers to the rescue
@Qualifier
@Target({ TYPE, METHOD,
PARAMETER, FIELD })
@Retention(RUNTIME)
@Documented
public @interface Translating {
}

26. Qualifiers to the rescue
@Translating
public class TranslatingWelcome extends Welcome {
@Inject GoogleTranslator translator;
public String buildPhrase(String city) {
return translator.translate("Welcome to " + city + "!");
}
}

27. Qualifiers to the rescue
@Translating
public class TranslatingWelcome extends Welcome {
@Inject GoogleTranslator translator;
public String buildPhrase(String city) {
return translator.translate("Welcome to " + city + "!");
}
}

28. Qualifiers to the rescue
@Translating
public class TranslatingWelcome extends Welcome {
@Inject GoogleTranslator translator;
public String buildPhrase(String city) {
return translator.translate("Welcome to " + city + "!");
}
public class Greeter {
}
@Inject @Translating
Welcome w; // No ambigiuty!
public void welcome() {
System.out.println(w.buildPhrase("Billund"));
}
}

29. @Produces
public class WelcomeProducer {
@Produces @Translating Welcome createWelcome() {
return new TranslatingWelcome();
}
}

30. Scopes
• JEE 6 provides a set of Scopes
• @Dependent, @ApplicationScoped,
@RequestScoped, @SessionScoped,
@ConversationScoped, <put your own here>
• Each have a context which are managed by
the container (you don’t have to do explicit
cleanup)

31. More CDI
• Event/Observers
• Stereo Types
• Alternatives
• API for Framework Implementors

32. Deep-dive Example
• PasteCode - part of the Weld Examples
• Uses just Servlet, CDI, JSF & EJB’s
• JEE 6 Web Profile

33. Challenges
• Persistence
• Validation of data from client to database
• Configuration of Servlet’s, EJB’s etc.
• Access to Beans from UI-Layer (EJB->JSF)
• Dependency Injection for decoupling concerns
• Setup things at Application Startup
• Cross-cutting custom business concerns (example Flood Control)
• Sending and receiving events
• Batch job’s
• ...and more

34. CDI Bean In Action
public class PasteWindow
{
...
private CodeFragmentManager
codeFragmentManager;t
public CodeFragment getCodeFragment()
{
return codeFragment;
}
…

35. CDI Bean In Action
@Named
public class PasteWindow
{
...
private CodeFragmentManager
codeFragmentManager;t
public CodeFragment getCodeFragment()
{
return codeFragment;
}
…

36. CDI Bean In Action
@Named
@RequestScoped
public class PasteWindow
{
...
private CodeFragmentManager
codeFragmentManager;t
public CodeFragment getCodeFragment()
{
return codeFragment;
}
…

37. CDI Bean In Action
@Named
@RequestScoped
public class PasteWindow
{
...
@Inject private CodeFragmentManager
codeFragmentManager;t
public CodeFragment getCodeFragment()
{
return codeFragment;
}
…

38. Persistence/Validation
@Entity
public class CodeFragment {
@Id
@GeneratedValue(strategy = AUTO)
@Column(name = "id")
private int id;
@Lob
@Size(min=1,
message="Must enter some text!")
private String text;
…
}

39. Application Startup
@Startup
@Singleton
public class PopulateDatabase {
@PersistenceContext
private EntityManager entityManager;
@PostConstruct
public void startup()
{
…
}
}

40. Sending and receiving events
@Inject
private Event<CodeFragment> event;
...
event.fire(code);
public void
addEntry(@Observes CodeFragment codeFragment)
{
this.log.add(codeFragment);
}

41. Cross-Cutting Business
@Decorator w/Decoratorimplements
public abstract class FloodingDecorator
CodeFragmentManager, Serializable
{
@Inject @Delegate
private CodeFragmentManage codeFragmentManager;
public String addCodeFragment(CodeFragment code,
boolean privateFragment)
{
...
return
codeFragmentManager.addCodeFragment(code,
privateFragment);

42. Summary
• JSR-299 provides a set of services for Java EE
• Bridges JSF and EJB
• Offers loose coupling with strong typing
• Extensive SPI for third-party integration with
Java EE
• Weld: JSR-299 Reference Implementation
• Seam 3: Portable extensions for Java EE

43. Q &A ?

44. Q &A ?
JEE 6 is
awesome!
Rate this talk: http://bit.ly/cdiaction

45. Q &A ?
• Weld - http://seamframework.org/Weld
• Seam 3 project - http://seamframework.org/Seam3
• Weld Maven archetypes for CDI and Java EE - http://tinyurl.com/
goweld
• Weld reference guide - http://tinyurl.com/weld-reference-101
• CDI JavaDoc - http://docs.jboss.org/cdi/api/latest/
• JBoss Developer Studio - http://devstudio.jboss.com
• JBoss Tools - http://jboss.org/tools