CDI, Weld and the future of Seam
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CDI, Weld and the future of Seam

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Recorded on 2010-04-30 at the Northern Virginia Software Symposium, a stop on the NFJS 2010 tour, this talk introduces JSR-299: Contexts and Dependency Injection for the Java EE platform (CDI), the ...

Recorded on 2010-04-30 at the Northern Virginia Software Symposium, a stop on the NFJS 2010 tour, this talk introduces JSR-299: Contexts and Dependency Injection for the Java EE platform (CDI), the new Java standard for dependency injection and contextual lifecycle management. It also covers Weld, the JSR-299 reference implementation, and explains how CDI will be used as the foundation for the next version of Seam (Seam 3).

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CDI, Weld and the future of Seam Presentation Transcript

  • 1. CDI (JSR-299), Weld and the future of Seam Dan Allen Senior Software Engineer JBoss by Red Hat
  • 2. Who am I? ● Author of Seam in Action, Manning 2008 ● Seam Community Liaison ● Weld, Seam & Arquillian project member ● JSR-314 (JSF 2) EG representative ● Open Source advocate mojavelinux 2 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 3. Agenda ● Terminology ● Why JSR-299? ● JSR-299 themes ● Brief tour of programming model ● Weld ● Seam 3 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 4. Technology terminology ● CDI (JSR-299) ● Contexts & dependency injection for Java EE ● Weld ● JSR-299 Reference Implementation & TCK ● Extended CDI support (Servlets, Java SE) ● CDI enhancements for extension writers ● Maven archetypes for CDI and Java EE ● Seam 3 ● Portable extensions for Java EE ● Integrations with non-Java EE technologies 4 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 5. Stated goal of JSR-299 Web tier Transactional tier (JSF) (EJB) 5 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 6. Why reinvest? Java EE 5 6 Seam 2 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 7. 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 7 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 8. 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 8 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 9. CDI: The big picture ● Fill in ● Catalyze ● Evolve 9 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 10. Why injection? ● Weakest aspect of Java EE 5 ● Fixed set of injectable resources ● @EJB ● @PersistenceContext, @PersistenceUnit ● @Resource (e.g., DataSource, UserTransaction) ● Name-based injection is fragile ● Not “refactor friendly” ● Requires special tooling to validate 10 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 11. JSR-299 theme @Produces @WishList Loose coupling... List<Product> getWishList() Event<Order> @InterceptorBinding @Inject @UserDatabase EntityManager @Observes @Qualifier ...with strong typing 11 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 12. Loose coupling ● Decouple server and client ● Using well-defined types and “qualifiers” ● Allows server implementation to vary ● Decouple lifecycle of collaborating components ● Automatic contextual lifecycle management ● Stateful components interact like services ● Decouple orthogonal concerns (AOP) ● Interceptors & decorators ● Decouple message producer from consumer ● Events 12 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 13. Strong typing ● Type-based injection ● Eliminate reliance on string-based names ● Compiler can detect typing errors ● No special authoring tools required ● Casting mostly eliminated ● Semantic code errors detected at application startup ● Tooling can detect ambiguous dependencies 13 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 14. Leverage and extend Java’s type system @Annotation <TypeParam> This information is pretty useful! Type 14 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 15. Who's bean is it anyway? ● Everyone throwing around this term “bean” ● JSF ● EJB ● Seam ● Spring ● Guice ● CDI ● Need a “unified bean definition” 15 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 16. Managed bean specification ● Common bean definition ● Instances are managed Managed by the container Beans ● Common services ● Interceptors ● Resource injections ● Lifecycle callbacks JSF EJB CDI JAX-RS ● Foundation spec How managed beans evolved: http://www.infoq.com/news/2009/11/weld10 16 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 17. CDI bean ingredients ● Auto-discovered ● Set of bean types ● Set of qualifiers ● Scope ● Bean EL name (optional) ● Set of interceptor bindings ● Alternative classification ● Bean implementation class 17 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 18. Welcome to CDI, managed beans! public class Welcome { public String buildPhrase(String city) { return "Welcome to " + city + "!"; } } 18 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 19. Welcome to CDI, EJB 3.1 session beans! @Stateless public class Welcome { public String buildPhrase(String city) { return "Welcome to " + city + "!"; } } 19 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 20. When is a bean recognized? ● Bean archive (WAR) ● Bean archive (JAR) beans.xml can be empty! 20 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 21. Injection 101 public class Greeter { @Inject Welcome w; public void welcome() { @Default qualifier implied @Default qualifier implied System.out.println( w.buildPhrase("Reston")); } } 21 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 22. Where can it be injected? ● Field ● Method parameter ● Constructor* ● Initializer ● Producer ● Observer 22 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 23. 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 23 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 24. The bean vs “the other implementation” ● Multiple implementations of same interface ● One implementation extends another public class Welcome { public String buildPhrase(String city) { return "Welcome to " + city + "!"; } } public class TranslatingWelcome extends Welcome { @Inject GoogleTranslator translator; public String buildPhrase(String city) { return translator.translate( "Welcome to " + city + "!"); } } 24 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 25. Quiz: Now which implementation gets injected? public class Greeter { private Welcome welcome; @Inject void init(Welcome welcome) { this.welcome = welcome; } ... } It's ambiguous! 25 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 26. Settling an ambiguous resolution ● Qualifier ● Alternative ● Hide bean types 26 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 27. qualifier n. an annotation used to resolve an API implementation variant at an injection point 27 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 28. Defining a qualifier ● A qualifier is an annotation @Qualifier @Retention(RUNTIME) @Target({TYPE, METHOD, FIELD, PARAMETER}) public @interface Translating {} 28 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 29. Qualifying an implementation ● Adding a qualifier annotation: ● makes type more specific ● assigns semantic meaning @Translating public class TranslatingWelcome extends Welcome { @Inject GoogleTranslator translator; public String buildPhrase(String city) { return translator.translate( "Welcome to " + city + "!"); } } 29 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 30. Qualifier as a “binding type” 30 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 31. Using a specific implementation ● Qualified implementation must be requested explicitly ● Akin to the factory method pattern ● Resolves ambiguity at injection point! public class Greeter { private Welcome welcome; No reference to implementation class! No reference to implementation class! @Inject void init(@Translating Welcome welcome) { this.welcome = welcome } public void welcomeVisitors() { System.out.println( welcome.buildPhrase("Reston")); } } 31 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 32. Alternative bean ● Swap replacement implementation per deployment ● Replaces bean and its producer methods and fields ● Disabled by default ● Must be activated in /META-INF/beans.xml Put simply: an override 32 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 33. Defining an alternative @Alternative public class TranslatingWelcome extends Welcome { @Inject GoogleTranslator translator; public String buildPhrase(String city) { return translator.translate( "Welcome to " + city + "!"); } } 33 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 34. Substituting the alternative ● Implementation must be activated using beans.xml <beans> <alternatives> <class>com.acme.TranslatingWelcome</class> </alternatives> </beans> 34 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 35. Assigning a bean name @Named("greeter") public class Greeter { private Welcome welcome; @Inject void init(Welcome welcome) { this.welcome = welcome; } public void welcomeVisitors() { System.out.println( welcome.buildPhrase("Reston")); } } 35 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 36. Assigning a bean name by convention @Named public class Greeter { private Welcome welcome; Bean name is decapitalized Bean name is decapitalized simple class name simple class name @Inject void init(Welcome welcome) { this.welcome = welcome; } public void welcomeVisitors() { System.out.println( welcome.buildPhrase("Reston")); } } 36 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 37. Welcome to CDI, JSF! ● Use the bean directly in the JSF view <h:form> <h:commandButton value="Welcome visitors" action="#{greeter.welcomeVisitors}"/> </h:form> 37 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 38. JSF managed JSP beans CDI Facelets 38 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 39. Stashing the bean in a context ● Bean saved for the duration of a request @RequestScoped @Named("greeter") public class Greeter { private Welcome welcome; private String city; // getter and setter hidden @Inject void init(Welcome welcome) { this.welcome = welcome } public void welcomeVisitors() { System.out.println(welcome.buildPhrase(city)); } } 39 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 40. 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> ● Satisfies initial goal of JSR-299 ● ...in fact, integrates JSF and any managed bean 40 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 41. Scope types and contexts ● Absence of scope - @Dependent ● Bound to lifecycle of bean holding reference ● Servlet scopes ● @ApplicationScoped ● @RequestScoped ● @SessionScoped ● JSF conversation scope - @ConversationScoped ● Custom scopes ● Define scope type annotation (e.g., @FlashScoped) ● Implement the context API in an extension 41 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 42. Scope transparency ● Scopes not visible to client ● No coupling between scope and use of type ● Scoped beans are proxied for thread safety 42 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 43. Conversation context ● Request <= Conversation << Session ● ● Boundaries demarcated by application ● Optimistic transaction ● Conversation-scoped persistence context ● No fear of exceptions on lazy fetch operations 43 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 44. Controlling the conversation @ConversationScoped public class BookingAgent { @Inject @BookingDatabase EntityManager em; @Inject Conversation conversation; private Hotel selected; private Booking booking; public void select(Hotel h) { selected = em.find(Hotel.class, h.getId()); conversation.begin(); } ... 44 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 45. Controlling the conversation ... public boolean confirm() { if (!isValid()) { return false; } em.persist(booking); conversation.end(); return true; } } 45 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 46. producer method n. a method whose return value produces an injectable object 46 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 47. 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 Custom setup Custom setup public List<Product> getWishList() { return em.createQuery("...").getResultList(); } 47 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 48. Bridging Java EE resources ● Use producer field to expose Java EE resource @Stateless public class UserEntityManagerProducer { @Produces @UserRepository @PersistenceContext(unitName = "userPU") EntityManager em; } @Stateless public class PricesTopicProducer { @Produces @Prices @Resource(name = "java:global/env/jms/Prices") Topic pricesTopic; } 48 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 49. Injecting resource in type-safe way ● String-based resource names are hidden public class UserManager { @Inject @UserRepository EntityManager userEm; ... } public class StockDisplay { @Inject @Prices Topic pricesTopic; ... } 49 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 50. Rethinking interceptors @Interceptors( SecurityInterceptor.class, TransactionInterceptor.class, LoggingInterceptor.class ) @Stateful public class BusinessComponent { ... } Um, what's the point? 50 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 51. Interceptor wiring in JSR-299 (1) ● Define an interceptor binding type @InterceptorBinding @Retention(RUNTIME) @Target({TYPE, METHOD}) public @interface Secure {} 51 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 52. Interceptor wiring in JSR-299 (2) ● Marking the interceptor implementation @Secure @Interceptor public class SecurityInterceptor { @AroundInvoke public Object aroundInvoke(InvocationContext ctx) throws Exception { // ...enforce security... ctx.proceed(); } } 52 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 53. Interceptor wiring in JSR-299 (3) ● Applying interceptor with proper semantics @Secure public class AccountManager { public boolean transfer(Account a, Account b) { ... } } 53 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 54. Multiple interceptors ● Application developer only concerned about semantics @Transactional public class AccountManager { @Secure public boolean transfer(Account a, Account b) { ... } } 54 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 55. Enabling and ordering interceptors ● Bean archive has no enabled interceptors by default ● Interceptors activated in beans.xml of bean archive ● Referenced by binding type ● Ordering is per-module ● Declared in module in which the interceptor is used <beans> <interceptors> <class>com.acme.SecurityInterceptor</class> <class>com.acme.TransactionInterceptor</class> </interceptors> </beans> Interceptors applied in order listed Interceptors applied in order listed 55 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 56. Composite interceptor bindings ● Interceptor binding types can be meta-annotations public @Secure @Transactional @InterceptorBinding Order does not matter Order does not matter @Retention(RUNTIME) @Target(TYPE) @interface BusinessOperation {} 56 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 57. Multiple interceptors (but you won’t know it) ● Interceptors inherited from composite binding types public @BusinessOperation class AccountManager { public boolean transfer(Account a, Account b) { ... } } 57 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 58. Wrap up annotations using stereotypes ● Common architectural patterns – recurring roles ● A stereotype packages: ● A default scope ● A set of interceptor bindings ● The ability to that beans are named ● The ability to specify that beans are alternatives 58 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 59. Annotation jam! ● Without stereotypes, annotations pile up public @Secure @Transactional @RequestScoped @Named class AccountManager { public boolean transfer(Account a, Account b) { ... } } 59 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 60. Defining a stereotype ● Stereotypes are annotations that group annotations public @Secure @Transactional @RequestScoped @Named @Stereotype @Retention(RUNTIME) @Target(TYPE) @interface BusinessComponent {} 60 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 61. Using a stereotype ● Stereotypes give a clear picture, keep things simple public @BusinessComponent class AccountManager { public boolean transfer(Account a, Account b) { ... } } 61 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 62. Events ● Completely decouple action and reactions ● Selectors tune which event notifications are received ● Can be observed: ● immediately, ● after transaction completion or ● asynchronously (via extension) 62 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 63. Firing an event Event instance with Event instance with type-safe payload type-safe payload public class GroundController { @Inject @Landing Event<Flight> flightLanding; public void clearForLanding(String flightNum) { flightLanding.fire(new Flight(flightNum)); } } 63 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 64. An event observer Takes event API type with Takes event API type with public class GateServices { additional binding type additional binding type public void onIncomingFlight( @Observes @Landing Flight flight, Greeter greeter, CateringService cateringService) { Gate gate = ...; flight.setGate(gate); cateringService.dispatch(gate); greeter.welcomeVisitors(); } } Additional parameters are Additional parameters are injected by the container injected by the container 64 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 65. Weld: JSR-299 Reference Implementation ● Developed under Seam project umbrella ● Version 1.0.1 available ● Bundled in JBoss AS 6 & GlassFish V3 ● Support for Tomcat, Jetty & Java SE ● CDI enhancements & utilities for extension writers ● Maven archetypes for CDI & Java EE 65 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 66. Seam’s mission statement To provide a fully integrated development platform for building rich Internet applications based upon the Java EE environment. 66 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 67. Seam 3: Key themes ● Portability ● Portable extensions run on any CDI implementation ● Modularity (i.e., Seam à la carte) ● Module per integration ● Individual module leads ● Independent release cycles ● “Stack” releases ● Strong tooling ● Java compiler ● JBoss Tools 67 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 68. Seam's new modular ecosystem 68 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 69. What's on the menu so far? ● Drools ● JavaScript Remoting ● JMS ● Security ● Faces ● Servlet ● International ● Wicket ● Persistence ● XML configuration ...and more  http://sfwk.org/Seam3 69 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 70. 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 70 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 71. End-to-end testing for Java EE ● SeamTest replacement ● ShrinkWrap ● Fluent API for creating Java archives JavaArchive archive = ShrinkWrap.create("archive.jar", JavaArchive.class) .addClasses(MyClass.class, MyOtherClass.class) .addResource("mystuff.properties"); ● Arquillian ● Integration test harness ● Pluggable container support (embedded or remote) ● Supports injection into test class ● Tests can be run from IDE or build script 71 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 72. 72 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 73. Summary ● JSR-299 provides a set of services for Java EE ● Bridges JSF and EJB ● Offers loose coupling with strong typing ● Catalyzed managed bean & interceptor specifications ● Extensive SPI for third-party integration with Java EE ● Weld: JSR-299 Reference Implementation ● Seam 3: Portable extensions for Java EE 73 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 74. How do I get started with CDI or Java EE 6? ● 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/ ● Any Java EE 6 container! 74 CDI (JSR-299), Weld and the future of Seam | Dan Allen
  • 75. Q&A Dan Allen Senior Software Engineer JBoss, by Red Hat http://in.relation.to http://seamframework.org/Seam3