2015 JavaOne EJB/CDI Alignment

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@dblevins @tomitribe #EJBCDI

EJB/CDI Alignment (What Does It Mean?)

David Blevins Tomitribe

Jean-Louis Monteiro Tomitribe

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CDI - EJB Alignment (understand the conversation)

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CDI History In Brief

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CDI Influences

• Dependency Injection

• Definite Spring influence

• Strong Google Guice syntax

• Originally called “WebBeans”

• Grew from Seam

• Glued JSF and EJB together

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CDI Behind the Scenes

• Achieved through sneaky interceptor trick

• Caused major delay to the Java EE 6 delivery

• Almost didn’t make it

• Criticized for going too far

• Stepped on EE toes (spec overlap)

• Stepped on SE toes (too “enterprisey”)

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CDI Rifts

• Creation of @ManagedBean spec at EE level

• Fuzzy aim at unifying EE component models

• Effort to not lose ground in EE

• Too ambiguous

• Creation of @Inject spec at SE level

• Fuzzy aim at being simpler version of the standard

• Effort to not lose ground in SE

• Too simple, no spec

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EJB Shortcomings

• Legacy

• Reputation

• Fully loaded by default

• Every method starts a transaction

• Throwing an exception destroys the instance

• Instances are non-concurrent

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CDI Takeover

• EJB adopts CDI (Java EE 6)

• JSF adopts CDI (Java EE 7)

• MVC adopts CDI (Java EE 8)

• JAX-RS considers CDI (Java EE 8)

• CDI moves to SE (Java EE 8)

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Result for EJB?

• Java EE 7

• Focus on realignment: @Transactional

• Java EE 8

• First spec round with no new EJB JSR

• Realignment stalled

• Awkward relationship

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CDI from an EJB perspective

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Proxy (Fake)

Proxy (Fake)

Interceptors

Decorators

Instance (Real)

Security

Transaction

Interceptors

Decorators

Instance (Real)

1. Resolution

2. Services

3. Invocation

(Pool)1. Resolution

2. Services

3. Invocation

(Context/Scope)

CDI 1.0 EJB 3.1

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Proxy (Fake)

Proxy (Fake)

Security

Transaction

Interceptors

Decorators

Instance (Real)

1. Resolution

2. Services

3. Invocation

(Pool)1. Resolution

2. Services

3. Invocation

(Context/Scope)

CDI 1.1 EJB 3.2

TransactionInterceptors

Decorators

Instance (Real)

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Lifecycle Lineup

• @Singleton

• same as CDI @ApplicationScoped

• @Stateful

• applies to any CDI Scope, not just @SessionScoped

• @Stateless

• no CDI equivalent

• @RequestScoped sort of close(ish)

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Awesome Power of Scopes

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http://tomitribe.io/projects/microscoped

http://tomitribe.io/projects/microscoped

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Common Mistakes you will make

• Not putting a beans.xml in your app (Java EE 6)

• No CDI for you!

• Not understanding @Typed

• Psst, think @Local from EJB

• Bites you when using @Produces

• Not understanding what Dependent and NormalScope

• Dependent == plain object

• NormalScoped == proxied object

• Bites you when creating custom scopes

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Biggest benefits of CDI

• Very active and open expert group

• Fully extendable

• Beans can be added at runtime

• Fully Open Source

• Spec is open source

• All implementations are open source

• Compliance test (TCK) suite is open source

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What is Aligned?

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Transactions - Aligned

• @TransactionAttribute & @ApplicationException

• Usable by

• @Stateless

• @Stateful

• @Singleton

• @Transactional (CDI equivalent, new in Java EE 7)

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Transaction - EJB flavor

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Transaction - CDI flavor

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Observations

• Pros

• New API is Better

• Doesn’t say “EJB”

• Cons

• Duplicating APIs

• Slight changes

• Conflicting usage?

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Observations - What happens?

• More work for servers to check for mistakes

• More work for IDEs to check for mistakes

• New users won’t know which to use and where

• Old users won’t remember how they are different

• One more place for us all to make mistakes and be confused

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When you still need EJB (not yet aligned)

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Security

• @RolesAllowed, @PermitAll, @DenyAll

• Usable by

• @Stateless

• @Stateful

• @Singleton

• Alignment

• Low likelihood

• Pandora’s box

• Not actively being discussed

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Startup

• @Startup

• Eagerly creates the instance upon startup

• Usable by

• @Singleton

• Alignment

• Strong Candidate

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Asynchronous

• @Asynchronsous

• Allows method calls to be asynchronous and return Future objects

• Usable by

• @Stateless

• @Stateful

• @Singleton

• Alignment


• Tracked in JIRA, high votes

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Schedule

• @Schedule

• Effectively Cron -- schedule invocations by minute or date, etc.

• Usable by

• @Stateless

• @Singleton

• Not @Stateful

• Alignment


• Could be a challenge -- timers are stateless, scopes are not

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Locking

• @Lock(READ) / @Lock(WRITE) / @AccessTimeout

• Allows for synchronization of methods without complex code

• Usable by

• @Singleton

• Not @Stateless

• Not @Stateful

• Alignment

• Medium Candidate

• Applying to CDI possibly easier than EJB

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MDBs

• @MessageDriven

• Connector-Driven Beans

• Usable by

• Not @Singleton

• Not @Stateless

• Not @Stateful

• Alignment

• Medium Candidate

• Pandora’s Box -- very complicated

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Thank You

2015 JavaOne EJB/CDI Alignment

Technology

Transcript of 2015 JavaOne EJB/CDI Alignment