J2ee web services(overview)

J2EE WEB-SERVICES
BY PRAFULL JAIN
2016BCEX1056
SEC-B , VIITH SEM

LIST OF CONTENTS:-
1. Application servers
2. What is J2EE?
3. Main Technologies
4. Application Scenarios
5. J2EE APIs and Services
6. EJB – a closer look

APPLICATION SERVERS
• In the beginning
Centralized, non-distributed
terminals
mainframe
terminals
3
In the 90’s, systems should be
client- server

APPLICATION SERVERS
4
Today, enterprise applications use the multi-tier model
“Multi-tier applications” have several independent components.
An application server provides the infrastructure and services to run such applications
Application server products can be separated into 3 categories:
 J2EE-based solutions
 Non-J2EE solutions (PHP, ColdFusion, Perl, etc.)
 And the Microsoft solution (ASP/COM and now .NET with ASP.NET, VB.NET,
C#,
etc.)

WHAT IS J2EE?
 It is a public specification that embodies several
technologies
 Current version is 1.5
 J2EE defines a model for developing multi-tier, web based,
enterprise applications with distributed components
J2EE BENEFITS
 High availability
 Scalability
 Integration with existing systems
 Freedom to choose vendors of application servers, tools, components
 Multi-platform

J2EE BENEFITS
 Flexibility of scenarios and support to several types of clients
 Programming productivity:
Services allow developer to focus on business.
Component development facilitates maintenance and reuse
Enables deploy-time behaviors Supports division of labor

MAIN TECHNOLOGIES
 JavaServer Pages (JSP)
 Servlet
 Enterprise JavaBeans (EJB)
JSPs, servlets and EJBs are application components.
JSP
 Used for web pages with dynamic content
 Processes HTTP requests (non-blocking call-and-return)
 Accepts HTML tags, special JSP tags, and scriptlets of Java code
 Separates static content from presentation logic
 Can be created by web designer using HTML tools

SERVLET
 Used for web pages with dynamic content
 Processes HTTP requests (non-blocking call- and-return)
 Written in Java; uses print statements to render HTML
 Loaded into memory once and then called many times
 Provides APIs for session management
EJB
 EJBs are distributed components used to implement business logic
(no UI)
 Developer concentrates on business logic
 Availability, scalability, security, interoperability and integrability
handled by the J2EE server
 Client of EJBs can be JSPs, servlets, other EJBs and external
aplications

Copyright 2002 © Paulo Merson
J2EE MULTI-TIER MODEL

J2EE Application Scenarios
 Multi-tier typicalapplication

 Stand-aloneclient

 Web-centricapplication

J2EE SERVICES AND APIS
 Java Message Service (JMS)
 Implicit invocation
 Communication is loosely coupled, reliable and asynchronous
 Supports 2 models:
 point-to-point
 publish/subscribe

JMS
 Point-to-point
 Destination is “queue”

JMS
 Publish-subscribe
 Destination is “topic”

 JNDI - Naming and directory services
 Applications use JNDI to locate objects, such as environment
entries, EJBs, datasources, message queues
 JNDI is implementation independent
 Underlying implementation varies: LDAP, DNS, DBMS, etc.
 Transaction service:
 Controls transactions automatically
 You can limit the transactions explicitly
 Or you can specify relationships between methods that make up a
single transaction

 Security




Java Authentication and Authorization Service (JAAS) is the new (J2EE 1.3)
standard for J2EE security
Authentication via userid/password or digital certificates
Role-based authorization limits access of users to resources (URLs, EJB methods)
Embedded security realm
 J2EE Connector Architecture
 Integration to non-J2EE systems, such as mainframes and ERPs.
 Standard API to access different EIS (GlassFish Server)
 Vendors implement EIS-specific resource adapters

 JDBC
 JavaMail
 Java API for XML Parsing (JAXP)
 Web services APIs

HOME INTERFACE
 Methods to create, remove or locate EJB objects
 The home interface implementation is the home object
(generated)
 The home object is a factory
REMOTE INTERFACE
 Business methods available to clients
 The remote interface implementation is the EJB object
(generated)
 The EJB object acts as a proxy to the EJB instance

TYPES OF EJB
StateFul
Statless
SessionBean Entity Bean Message Driven
Bean
BMP
CMP
Enterprise Bean

SESSION BEAN
 Stateful session bean:
 Retains conversational state (data) on behalf of an individual
client
 If state changed during this invocation, the same state will be
available upon the following invocation
 Example: shopping cart
 Stateless session bean:
 Contains no user-specific data
 Business process that provides a generic service
 Container can pool stateless beans
 Example: shopping catalog

ENTITY BEAN
 Represents business data stored in a database  persistent
object
 Underlying data is normally one row of a table
 A primary key uniquely identifies each bean instance
 Allows shared access from multiple clients
 Can live past the duration of client’s session
 Example: shopping order
 Bean-managed persistence (BMP): bean developer writes JDBC code
to access the database; allows better control for the developer
 Container-managed persistence (CMP): container generates all JDBC
code to access the database; developer has less code to write, but also
less control

MESSAGE-DRIVEN BEAN
 Message consumer for a JMS queue or topic
 Benefits from EJB container services that are not available
to standard JMS consumers
 Has no home or remote interface
 Example: order processing – stock info

SOURCES & RESOURCES
 The J2EE Tutorial. Sun Microsystems
 www.java.sun.com/j2ee
 www.theserverside.com
 www.Wikipedia.com/j2ee
 www.javatpoint.com

J2ee web services(overview)

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