ILP J2EE Stream J2EE 07 Othertech v0.3

8/14/2019 ILP J2EE Stream J2EE 07 Othertech v0.3

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Overview of other J2EEtechnologiesVersion 1.0


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September 3, 2009TCS Internal

Introduction

The three primary components of J2EE

application are:Servlet

JSP

EJBIn addition to these, J2EE provides additionaltechnologies which helps in building J2EEapplications.

This session is an overview of all thesetechnologies.


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Technologies

Java Messaging Service

JavaMail

JNDI

JAAS


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Java Messaging Service (JMS)

JMS is a wrapper API that standardizes

messaging functionality of other serviceproviders such as IBM MQSeries, etc.

JMS does not provide any services directly.

It facilitates to access messaging facilitiesprovided by different messaging-serviceprovider.


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Messaging

Messaging is a means by which distributed

applications communicate with each other.A message is a self-contained package ofbusiness data and routing headers.

Message based applications communicateasynchronously through a message server.

Services that support message-basedapplications are known as message-oriented

middleware.


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JMS Features

JMS supports clustered, high-availability

message servers.JMS supports transaction to ensure thatrelated messages are either delivered

together or not at all.JMS messages can be accessed/processedby message driven beans.

JMS, unlike RMI helps create loosely coupled

applications.


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Message Structure

Headers

Fixed set of metadata fields

Properties

Set of key-value pairs used for application

specific purpose.Body

The actual content to be sent.


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Message TypesByteMessage

A stream of bytesMapMessage

A set of key-value paiars

ObjectMessageSerialized object instance

StreamMessage

A stream of primitives

TextMessage

A String instance


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Types of Messaging

Point-to-point messaging

Messages send through queues.

Only one consumer can consume amessage.

Publish-and-subscribe messagingMessages are sent through topics.

Many subscribers can consume messages.


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Message ComponentsDestinations

Place where the message is sent.Specific type of destinations are queues

(point-to-point systems) and topics(publish-subscribe) systems.

Destinations are configured by messagingserver.

Destinations are not created byapplication, but can be obtained by JNDIlookup.

Connections

This represents the connection between

the application and messaging server overwhich messa es can be sent.


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Message Components (Contd.)Connection Factories

Connections cannot be directlyinstantiated.

Connection factory creates connectionobjects.

Connection factory is found by JNDIlookup.

Sessions

Messages are not directly sent andreceived.

Session serves as a factory which is usedby message, producers and consumers.

Session provides transactional behavior


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Message Components (Contd.)

Producers

Producers represent objects whichproduce message.

Consumers

Consumers represent objects whichconsumer message.


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Java Mail

JavaMail API is an abstract suite of classes

for handling message-based systems.JavaMail makes it easy to incorporatecomplete e-mail connectivity within any Javaprogram, Servlet, bean, or applet.


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Mail Protocols

Protocols define the way mails are packages

and sent.The three popular mail transfer protocolsare:

SMTP (Simple Mail Transfer Protocol)Designed to deliver mails to server

POP3 (Post Office Protocol Version 3)

Popular mechanism to collect/read mails. Internet Message Access Protocol (IMAP)

Rich set of functionalities.


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JavaMail FunctionsThe major functions of JavaMail API are:

Session ManagementManages all aspects of communication

Means for mail to interact with network

Message ManipulationUsed to create and manipulate mails.

Mail Storage and Retrieval

Used to store mails in hierarchical

structure.Transportation

Takes care of delivery of mails.


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JAAS

JAAS stands for Java Authentication and

Authorization Services.JAAS is the security mechanism ofpreventing unauthorized users into J2EEapplication.


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JASS Mechanisms

Authentication services

These services ensure that every user isauthorized to use system and its resources

This essentially matches with the

underlying operating systems accessmechanism.

Authorization services

These services associate a set ofpermissions with each user.

This helps in granting differing levels ofaccess to different users.


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JAAS Security Realms

JAAS Security Realm is a logical grouping of

users and services that make sense.It may be:

Users using a particular machine

Users working for a company / division /workgroup.


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JNDI

Naming service essentially translates

human-friendly names to machine-friendlynames.

Normally these are called directory servicesassociating names as well as assign someadditional attributes.

Directory services are important in networkinfrastructure, because they enable users

and applications to look up networkresources.

JNDI provides a set of API that providedirectory and naming services to Javaapplications.


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JNDI Packages

Naming

Used to access simple naming services.

Directory

Used to access directory services.

EventHandles event notification

LDAP

Deals with LDAP controls and operationsSPI

Consists of Service Provider Interface (SPI)

classes and interfaces used by LDAP


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Java Transaction API (JTA)

All transactions with the database should be

atomic with ACID property.In normal applications local transactiontakes place which is easy to manage.

In distributed applications, variousapplications will be involved in transactionand somebody should take care.

JTA provides interface that can communicate

with JTS (Java Transaction Service).


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Reference

James Mc Govern, et. al., J2EE 1.4. Bible

S Allamaraju, et. al., Professional Java ServerProgramming, J2EE 1.3 Ed.

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ILP J2EE Stream J2EE 07 Othertech v0.3

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