Enterprise Java Beans Part I

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Enterprise Java BeansPart I

• Kyungmin Cho
• 2001/04/10

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Agenda

• JavaBeans and Enterprise JavaBeans
• EJB component model
• EJB Architecture

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• JavaBeans and Enterprise JavaBeans

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Defining Enterprise JavaBeans(1)

• A server-side component architecture
• Model to enable efficient development and
  deployment of Java applications
• Transactional,Portable
• Distributed,Multi-tier
• Scalable
• Secure

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Defining Enterprise JavaBeans(2)

• EJB is not JavaBeans
• a Server Component specification for Java
• Separates business and system programming
• Portability of business objects
• Extensibility through vendor features

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Defining JavaBeans(1)

• A client-side component architecture
• Portable, platform-independent component model
  written in the java programming language
• Acts as a bridge between proprietary component
  models
• Provides a seamless and powerful means for
  developers to build components that run in
  ActiveX container applications

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Defining JavaBeans(2)
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JavaBeans Vs. Enterprise JavaBeans(1)

• JavaBeans
• Can be either visible or non-visible
• Client gt Server
• Java.bean.
• Intra-processor
• Easier to develop than EJB

• EJB
• Are decidedly non-visible, remote objects
• Server
• Javax.ejb.
• Inter-processor
• More difficult to develop than JavaBeans

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JavaBeans Vs. Enterprise JavaBeans(2)
Server
Enterprise information Services
Client
Java Beans
Container
Java Beans
Database
EJB1
Java Beans
Existing application
EJB2
Client
EJB3
Java Beans
Server manages resources such as threads,
connection pooling, caching, and state
management
Java Beans
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Agenda

• JavaBeans and Enterprise JavaBeans
• EJB component model
• EJB Architecture

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• EJB component model

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What is component?

• Components are made by assembling objects.

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Component System

• Component system is fundamental for assembling
  and managing components.

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Client component

• Component button, list, spread sheet, etc.
• Container window, form, etc.

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Server component(1)

• Component
• Interface is separated from implementation.
• Container
• Manages message-passing between client and
  component
• Automatically carry out standard infrastructure
  services such as transaction and security, etc.

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Server component(2)
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Agenda

• JavaBeans and Enterprise JavaBeans
• EJB component model
• EJB Architecture
• What can we do with EJB?

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• EJB Architecture

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EJB Design Goals

• Simplify development/deployment of distributed
  applications
• Achieve broad industry acceptance
• The right expert focuses on the right job
• Platform independent and protocol neutral
• Enable development of portable components - Truly
  enable reuse

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EJB Architecture
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What Is Special About EJBs?

• Learn once
• Write Once, Run Anywhere TM
• Portable and interoperable
• Flexible and extensible
• Scalable
• Easier to write distributed applications
• Transaction management
• CORBA compatible

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EJB Architecture Roles

• Bean provider
• Container provider
• Server provider
• Application assembler
• Deployer
• System administrator

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Application Life Cycle
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EJB component feature(1)

• Include business logic
• Produce and manage instance at run time
• Can be customized by editing environment entry.
• Service information is separated from EJB class.
  This makes Service information to be managed by
  tools when assembling and deploying application.
• Client can access EJB through container.

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EJB component feature(2)

• If EJB uses services which are defined in EJB
  specification, EJB can be deployed in all EJB
  containers.
• EJB dont need recompiling and editing source
  code.

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EJB Server(1)

• Provides System Services
• Transaction support
• Database access
• System resource
• Namespace
• Implementations
• Middleware servers
• Application servers
• Database servers

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EJB Server(2)

• Supplies containers for EJBs
• API between server and container is currently
  vendor specific
• Server could provide several container
• types to provide various extended
• services to different beans

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EJB container(1)

• Currently provided by EJB Server
• EJB access to server resource through standard
  API
• May Contain one or multiple classes
• Tools for EJB creation and deployment

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EJB container(2)

• Some standard services
• Persistence
• EJB instance creation location
• Namespace
• Transaction control
• Swapping
• Security
• Custom services
• Application-specific
• Bridge to existing systems