EJB 3.1 by Bert Ertman

Enterprise JavaBeans 3.1

Bert [email protected]

Enterprise JavaBeans 3.1Bert Ertman

Technology Manager

Competence Center Java

Co-‐lead NLJUG, Sun/Oracle recognized Java Champion

Author and editorial board member

for Dutch Java Magazine

E-‐mail: [email protected]

Follow me on TwiLer: @BertErtman

mailto:[email protected]

mailto:[email protected]

#fail

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EJB

J2EE

BeJUG Evening Session - Enterprise JavaBeans 3.1


Agenda

• EJB 3: short recap

• What’s new in EJB 3.1

• Ease-of-use improvements

• EJB Lite

• New features


The 3 minutes introduction to EJB 3


Example: EJB 2.x Session Bean


Example: EJB 2.x Deployment Descriptor


Example: EJB 2.x Client View


painful truth of reality?blissful ignorance

or


Example: EJB 3.x Session Bean


Example: EJB 3.x Deployment Descriptor


Example: EJB 3.x Client View


How did they do that?

• Configuration by exception with sensible defaults

• Transaction type defaults to CONTAINER

• Transaction attribute defaults to REQUIRED

• Security permissions defaults to UNCHECKED

• Use Annotations

• To choose explicitly (recommended)

• To override defaults

• Deployment descriptor is no longer required

• But can override above configurations


EJB 3 Programming Model

1. Call a method

2. Invokes middleware services: Lifecycle mgmt, trx mgmt,

Persistence, security, etc.

3. Invoke corresponding method on bean class

4. Return outcome

4. Return from call


So, what’s new in EJB 3.1?


EJB 3.1

• Separate JSR (318)

• Evolve separately from JPA

• Focus on ease-of-use

• Expert group formed - Aug 2007

• Final release - December 2009


Ease-of-use improvements

• Optional Local Business interface

• Simplified packaging

• EJB-Lite

• Portable JNDI names

• Simple component testing


Example: Session Bean with Local Business interface


Example: Session Bean without Local Business interface


Simplified packaging

• Goal is to remove artificial packaging restrictions

• All resources are shared within .war

• Web application APIs are not exposed to EJB components

• ejb-jar.xml is still optional

• If needed, placed in WEB-INF


Java EE 5 packaging


Simplified packaging


EJB 3.1 lite


EJB 3.1 “Lite”

• Small subset of EJB 3.1 API required by Java EE 6 Web Profile

• Broadens the availability of EJB technology without losing portability


EJB HEAVY

EJB lite

Specs are ok:

Blond hair,blue eyes,red lips,

pink thong...

BUT...


Lite vs Full

• EJB Lite:

• Local Session Beans

• CMT / BMT

• Declarative Security

• Interceptors

• Web Profile also includes JPA 2.0

• Full = Lite + ...

• Message Driven Beans

• EJB Web Service Endpoints

• RMI-IIOP Interop

• 2.x / 3.x Remote view

• 2.x Local view

• Timer Service

• CMP / BMP Entities


Portable global JNDI names

• Spec-defined lookup names for Remote and Local session beans

• Three main goals :

• Simplify intra-application Local Session lookups

• Simplify mapping of cross-application Remote session bean dependencies

• Improve portability of Remote Java clients


Portable naming syntax

• Each session bean gets the following entries :

• Globally unique name:java:global[/<app-name>]/<module-name>/<ejb-name>

• Unique name within same application:

java:app[/<module-name>]/<ejb-name>

• Unique name within defining module:

java:module/<ejb-name>


Example: remote session bean with remote client

Bean deployed as part of hello.jar


EJB component testing

• Session Beans were always hard to test

• Unit-testing was possible, but what about container resources?

• Automated integration testing required

• Now supported with in-process EJB container


Embeddable API

• Portable API for running EJB components in same process as client code

• Same component behavior / life cycle as server-side

• CMT/BMT, injection, threading guarantees, ...

• “Single Application” model

• Only required to support 3.1 “Lite” API

• Vendors can optionally support additional functionality


Example: Embeddable API


New features

• Singletons

• Startup / shutdown callbacks

• Calendar-based timers / automatic timer creation

• Asynchronous invocations

• JAX-RS integration


Singletons

• One instance per application, per JVM

• Not intended to provide cluster-wide singleton

• Fits into existing dependency injection architecture

• Access through @EJB or lookup

• Intended for sharing data within entire application (not just EJB components)

• Designed for concurrent access


Lifecycle of a singleton session bean

Does not exist

Method-ready

Class.newInstance()Dependency injections@PostConstruct

@PreDestroy

Business method


Example: simple singleton usage


Singleton concurrency options

• Single threaded (default)

• For consistency with all existing bean types

• Container Managed Concurrency

• Control access via method-level locking metadata

• Bean Managed Concurrency

• All concurrent invocations have access to bean instance


Container Managed Concurrency

• Concurrent access determined by method-level locking metadata

• READ lock: allow any number of concurrent accesses to bean instance

• WRITE lock (default): ensure single-threaded bean instance access

• Incoming invocations are blocked by container until the necessary lock can be acquired

• … or until an optional timeout has been reached


Example: read-only singleton (container managed)


Example: read-mostly singleton (container managed)


Bean Managed Concurrency

• All incoming invocations allowed to access bean instance concurrently

• Bean developer is solely responsible for maintaining integrity of instance state

• Can use synchronization primitives such as synchronized, volatile


Example: bean managed concurrency


Application Startup/shutdown callbacks

• Uses singleton bean life cycle

• Full container services available

• Container-managed transactions

• Entity Managers, Timer Service, etc.

• Startup callback:

• @Startup and @PostConstruct

• Shutdown callback:

• @PreDestroy


Example: startup/shutdown callbacks


Timer Service enhancements

• Calendar-based timeouts

• Automatic timer creation

• Non-persistent timers


Example: EJB 3.0 use of Timer Service


Some (hard) lessons learned...

• Difficult to configure calendar-based events using only relative time units

• How to register the timer in the first place?

• Typical container events not a great fit; they happen every time application initializes and in every server instance

• Burden is on developer to figure out if timer already exists

• No way to guarantee that only one is created per cluster


Calendar based timeouts

• Cron-like semantics with improved syntax

• Can be created programmatically or automatically

• Named attributes:

• second, minute, hour (default = “0”)

• dayOfMonth, month, dayOfWeek, year (default = “*”)

• Relative to optionally specified time zone


Calendar expression examples

• The last Thursday in November at 2 pm:

• (hour=”14”, dayOfMonth=”Last Thu”, month=”Nov”)

• Every day at 3:15 am U.S. Eastern Time:

• (minute=”15”, hour=”3”, timezone=”America/New_York”)

• Every twenty seconds:

• (second=”*/20”, minute=”*”, hour=”*”)


Automatic Timer creation

• Container creates timer automatically when application is being deployed:


Example: non-persistent timers


Simple asynchronous operations

• Use metadata to mark a Local/Remote business method as asynchronous

• Container returns control to client before executing business method

• No separate API to learn


Example: local concurrent computation


Asynchronous results

• Based on java.util.concurrent.Future

• Result value is returned via Future.get()

• Also supports Future.get(long, TimeUnit)

• Client exception wrapped by ExecutionException

• getCause() returns same exception as would have been thrown by a synchronous invocation


Example: Asynchronous operation result

AsyncResult<V> implements Future<V>


JAX-RS support

• Java API for XML RESTful Services

• JSR-311 annotations can be used within Stateless Session Beans


Example: Session Bean as JAX-RS resource

Rod, I am your father

Lean Java EE 6 without Spring

Springvs

Java EE 6

“Now that Java EE 6 is here…do I still need those proprietary frameworks?”

“Java EE 6 provides similar benefits without tying you to a non-standard solution”

http://press.redhat.com/2010/10/12/now-that-java-ee-6-is-here-do-i-still-need-those-proprietary-frameworks/







Soon, in a store near you...

Javawith EJB !!!

Bert Ertman“I wrote this book for architects and developers who have grown increasinglyfrustrated with that annoying rebelframework called Spring. It shows what you can do to implement cleaner, more productive and above all STANDARD code for development of first class web applications.”


Questions?

EJB 3.1 by Bert Ertman

Technology

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