Topic4 Application Servers

Application Servers How Application Servers help application integration? Sanjoy Sanyal (Tech for NonGeek)

The Basic Issue

Connecting remote clients with applications over Internet

… and integrating applications over the Net

… .pose a few challenges in application integration

Sanjoy Sanyal (Tech for NonGeek)

Application Servers

Application servers was one response to the challenge

Vendors try to provide middleware logic

For e.g. for transactions, security, persistence

Functionality is similar to CORBA, TP monitors and message brokers

The goal is to provide an environment for hosting all kinds of application logic:

Can be used for EAI as well as Web-based integration

Two dominant platforms : J2EE and .NET

(we will use J2EE as an example in next slides)

J2EE: Main Components Sanjoy Sanyal (Tech for NonGeek) Servlets JavaMail Java API for XML Processing (JAXP) JavaServer Pages (JSP) Java transaction API (JTA) Enterprise Java Beans (EJB) Java Authentication and Authorization Service (JAAS) Java Message Service (JMS) Java Naming and Directory Interface (JNDI) Java DataBase Connectivity (JDBC) Java 2 Connector Architecture (J2CA) Support for communication and presentation Support for application integration Support for access to resource managers

Support for the Application Layer: EJB

Support for application logic thru: EJB, JNDI and JMS

EJB (Enterprise Java Beans) is at the core of J2EE

Server-side component: provides application specific functionality

Specifies three different types of beans:

Session beans handle a session with a client. Can be stateful or stateless. E.g.: shopping cart (stateful)

Entity beans live beyond the boundary of a client session. They have a state and are in persistent storage

Message-driven beans cater to asynchronous interaction with clients

EJB container provides the environment in which the beans run

All interactions between the EJB and other objects go thru the container

Provides services like transactions, persistence, security (developers need not implement this functionality)

Support for the Application Layer: JNDI

Java Naming and Directory Interface defines an interface for directory services:

Does not mandate an implementation

In general, allows clients to bind to a server based on the object name

Allows binding to EJBs, in the J2EE context

Connecting to Resource Layer: JDBC & J2CA

JDBC:

API that allows developers to connect to a tabular data source by executing SQL commands from a Java program

JBDC methods can be called from an EJB or directly from a servlet (bypassing access to an application logic layer)

J2CA:

Generalization of JDBC approach

Defines how to build resource adapters

java components that can help EJB and other Java applications interface with resource managers

Characterized by contracts which define the API that Java applications can use to access the resource manager

Support to the application logic layer Sanjoy Sanyal (Tech for NonGeek) EJB JNDI JDBC EJB EJB EJB Container JMS J2CA resource adapter J2CA resource adapter Other adapters Application logic layer Presentation layer

Support to Presentation Layer

This support differentiates application servers from conventional middleware

Application servers provide presentation and personalization features for a variety of clients:

Web browsers, applications, devices, E-mail programs, Web services clients

Support to the presentation layer Sanjoy Sanyal (Tech for NonGeek) Multi-device content delivery Servlets Personalization logic JSPs XML support Web services support Presentation layer Application logic layer Connection to resource management layer Resouerce management layer Web Server Email Server WAP Servers

Summary