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Java 2 Enterprise Edition(J2EE)

Presented By: Mohamed Mansour

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Notes

• WebSphere lab– Thursday (3/17) 3:00-5:00 PM– Room 153 CCB– www.cc.gatech.edu/~mansour/6210.html

• Extra credit project– Due Friday, April 1, at midnight– Contact mansour@cc for details

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Outline

• Introduction & Motivation

• Enterprise Applications

• J2EE Architecture

• Server Side Components

• Q&A

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Enterprise Applications

• Inter-company integration

• Intra-company integration

• Legacy applications

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Enterprise ApplicationsEnd-User View

eBay.com

hotmail.com

my.SAP.com

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Enterprise ApplicationsIntra-Enterprise

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Enterprise ApplicationsInter-Enterprise

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Challenges

• Interoperability

• Interface Complexity

• System Evolution

• Scalability

• Reliability

• Cost

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Current Solutions

• Hide complexity in standard application server architectures– .NET, J2EE, other…

• Technology independent interfaces– XML and Web Services

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J2EE Architecture

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Request Dispatcher

Large Scale Deployment

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Multi-Application Hosting

J2EE Server

App B

App C

App D

App A

App A

• Multiple applications on same server

• Statistical multiplexing over different request types

• Can we provide performance isolation guarantees between different applications?

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J2EE ServerJ2EE Server

App B

App C

App D

App A

App AApp C

App B

Request Dispatcher

Multi-Application Hosting

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EJB Container Services

• Persistence

• Transactions

• Caching

• Clustering

• Security

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EJB Types

• Entity Beans– Persistent objects with primary keys– Container Managed Persistence (CMP)– Bean Managed Persistence (BMP)

• Session Beans– Stateless– Stateful

• Message Driven Beans (MDB)

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EJBObject

Interface

RMI-IIOP

JVM 1 JVM 2

Calling Methods on EJBs

ClientServer

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EJB

JVM 1 JVM 2

Calling Methods on EJBs

ClientServer

JNDI

Home“ejbs/ejb/MyEjbHome”

1. Lookup the home interface

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EJB

JVM 1 JVM 2

Calling Methods on EJBs contd

ClientServer

JNDI

2. Use Home interface to obtain object interfacefrom server

Home

Home“ejbs/ejb/MyEjbHome”

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EJB

JVM 1 JVM 2

Calling Methods on EJBs contd

ClientServer

JNDI

3. Use object interface to invoke server methods

Home

Home“ejbs/ejb/MyEjbHome”

Object Interface

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Code SampleInitialContext ic = new InitialContext();

MyBeanHome home = (MyBeanHome) ic.lookup("java:comp/env/ejb/MyBeanHome")

MyBean b = (MyBean) home.create();

b.foobar();

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EJB

Home

Object Interface

Local View

HomeObject

Interface

Remote View

Direct calls

RMI-IIOP

JVM 1

JVM 2Local Interfaces in J2EE 2.0

Server

Client

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EJB ref name: “myEjbRef”JNDI name: “ejbs/ejb/MyEjbHome”EJB

JVM 1 JVM 2

EJB References

ClientServer

JNDI

Home“ejbs/ejb/MyEjbHome”

ic.lookup(“myEjbRef”)

XML configuration file

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Using Remote Interfaces

Entity Bean

Entity Bean

Entity Bean

Entity BeanClient

RMI-IIOP

EJB Container

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Using Remote Interfaces

• Network overhead for each call

• Separate transaction for each call– Entity beans have inconsistent state– Recovery must be performed at client side– Extra database statements (even for simple

set methods)

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Using Local Interfaces

SessionBean

Entity Bean

Entity Bean

Entity Bean

Entity BeanClientRMI-IIOP

EJB Container

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Q&A

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References

• http://java.sun.com/products/ejb/

• http://java.sun.com/products/jdk/rmi/

• http://wwws.sun.com/software/jini/

• http://java.sun.com/j2ee/1.4/docs/tutorial/doc/index.html

• http://www.w3.org/2002/ws/

• http://www.onjava.com/pub/a/onjava/2004/11/03/localremote.html