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Enterprise Java Beans- in the enterprise

Harald Søvik, [email protected]


About

M. Sc. Computer Science at NTNU 2006

Employed by Computas (2.5 years)

Technical developer

Technical project manager


About contd.

Mattilsynet (Norwegian FDA)

• 20 developers, 20 domain experts

• 4 years of development

• ~500 simul. users, 50 000 total web users

• Integration with ~40 other systems• web services, file/ftp, file/email (!)

• Case management

• Workflow oriented


Outline

Enterprise applications

EJB components

EJB primary services

Examples



include:

• Online shopping

• Order/billing systems• pda/mobile/tablet

• Personel/payroll systems

• Case management and workflow -systems



exclude:

• Embedded systems

• Games (..)

• Operating systems

• Personal applications• Word processors

• Spread sheet


2-tier architecture



Large database

• > 100 GB

Many simultaneous users

• > 1000

Integrations

• web services, file/ftp


3-tier architecture


Problems

Security

• Clients with database-connection• No data validation

• Web clients • Injection

• «Client side security»• No such thing


Problems - contd.

Performance

• Connection pooling

• Network connectivity

Transactions

Scalability

Reliability

Integration


EJB Components

Entites• Persistence – save data

Session beans

• Stateful• Client sessions – process data

• Stateless• One-shot method invocation, webservice – process data,

receive data

Message driven beans• Asynchroneous – receive data


Entities

High-level abstraction of JDBC

Maps tables to objects

• Object to Relational Mapping (ORM)

Plain Old Java Objects (POJOs)

EntityManager

E.g. Person


Session beans

Remotely accessible methods

• Resides on the server Isolates business logic

• Client: view and edit data

• Server: process and save data Coarse grained methods

• High cohesion, low coupling Two kinds

• stateless and stateless


Stateful session beans

Models actions across time

• business processes, workflow, taskflow

• maintains conversational state

E.g. PersonRegister

• .initApplication(..)

• .registerDetails(..)

• .calculateRisk(..)


Stateless session beans

Models instant actions

• Disposable, pooled instances

• RMI invocation

• WebService invocation

E.g. SearchManager

• search(..)


Message Driven Beans

Models reception of messages

• Asynchroneous

• Envelope + letter

• Listen to Queue or Topic

• Can gurantee delivery

E.g. RegisterUpdatesMDB

• onMessage()


Message Driven Beans contd.

The Java Message Service (JMS) API is a messaging standard

allows application components based on the Java 2 Platform, Enterprise Edition (J2EE) to create, send, receive, and read messages. It enables distributed communication

is loosely coupled, reliable, and asynchronous.

may be integrated with the application server using the J2EE Connector Architecture.


The Container

Manages the beans

• «deploy»

• pool

• activate

• passivate

• destroy


The Container contd.

JBoss

IBM WebSphere

BEA WebLogic

Oracle Application Server (OC4J)

Sun Glassfish

.. and your beans are portable !


Primary Services

Concurrency Transactions Persistence Distributed Objects Asynchronous Messaging Timer Service Naming Security


Examples

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