J2EE

John D. McGregor

Clemson University

johnmc@cs.clemson.edu

Functionality

Support for secure commerce over the Internet

Support for secure services over the Internet

Serve clients

Qualities

Flexibility

Modifiability

Reliability

Buildability

Maintainability

Performance

4-tier systems

JavaTechnologies

JDBC

JNDI

EJB

RMI

JSP

Servlets

XML

JDBC

Java Data Base Connectivity

Establishes connections among applications and databases

This may be direct or indirect

Need to be able to administer database without involving the client

JNDI

Java Naming and Directory Interface

Provides a consistent interface to enterprise wide directories

EJBs

Java Servlet

Serverside application that extends a web server

Communicates using POST and GET

Remote Method Invocation - RMI

Interface Definition Language

A language for specifying object interfaces

Uses a simplified type system

The CORBA version interfaces multiple languages

Java Transaction Architecture

A basic CORBA OTS transaction monitor

JavaMail

API for accessing mail servers

Java Messaging Service - JMS

Communicating with message-oriented middleware

Point-to-point domain

Publish/subscribe domain

Extensible Markup Language

XML

Platform independent

A number of standard tags have been developed to facilitate the transfer of information between companies

Our focus

JSP – Model 1

JSP – Model 2

JSP

JSP

<%@ page language="java" %>

<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>

<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>

<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>

<html>

<head>

<title>Submit example</title>

</head>

JSP

<body>

<h3>Example Submit Page</h3>

<html:errors/>

<html:form action="submit.do"> Last Name: <html:text property="lastName"/>

<br> Address: <html:textarea property="address"/>

<br> Sex: <html:radio property="sex" value="M"/>Male <html:radio property="sex" value="F"/>Female

<br> Married: <html:checkbox property="married"/>

<br> Age: <html:select property="age"> <html:option value="a">0-19</html:option> <html:option value="b">20-49</html:option> <html:option value="c">50-</html:option> </html:select>

<br> <html:submit/> </html:form> </body> </html>

Use of JSP

Person

                 FirstName String

                 SecondName String

                 Salary     int

               ;

EJB

EJB

This is the so-called “middleware”

Comparable to the Microsoft Transaction Server and components

The “application server” provides/ or is a bean container

EJB

The J2EE security model lets you configure a Web component or

          enterprise bean so that system resources are accessed only by

          authorized users.

The J2EE transaction model lets you specify relationships among

          methods that make up a single transaction so that all methods in one

          transaction are treated as a single unit.

JNDI lookup services provide a unified interface to multiple naming

          and directory services in the enterprise so that application

          components can access naming and directory services.

The J2EE remote connectivity model manages low-level

          communications between clients and enterprise beans. After an

          enterprise bean is created, a client invokes methods on it as if it were

          in the same virtual machine.

EJB- Transactions

Any good database software supports a transaction model that provides

Read/write

Commit

Rollback

EJB uses Java SQL to talk to database

Database handles the actions

Trade-off: how often is data committed?

EJB - Concurrency

One bean asks whether a certain item is available. While that user makes up his mind, another bean asks the same question and quickly buys the bean. The first bean assumes that the item is still available and marks it as sold.

EJB has locking capability. Can block access by others until commit or rollback ends the transaction

EJB - Concurrency

Beans

can not create threads

Can not access threads with java.io

Can not operate directly on sockets

Can not use AWT to interact with user

Only use parameter types allowed by RMI

Must supply a no argument constructor

EJB - persistence

CMP – container managed persistence

Beans are portable

Caching happens at an aggregated level

BMP – bean managed persistence

Beans are not as portable

Caching is local

EJB Deployment

An EJB is a set of Java classes and an XML file

XML manifest locates resources that the bean will need

Specifies services that the bean offers

Web services

Web Services Models

Service view of Web services


	Support for secure commerce over the Internet
	Support for secure services over the Internet
	Serve clients


	Flexibility
	Modifiability
	Reliability
	Buildability
	Maintainability
	Performance


	Java Data Base Connectivity
	Establishes connections among applications and databases
	This may be direct or indirect
	Need to be able to administer database without involving the client


	Java Naming and Directory Interface
	Provides a consistent interface to enterprise wide directories


	Serverside application that extends a web server
	Communicates using POST and GET


	A language for specifying object interfaces
	Uses a simplified type system
	The CORBA version interfaces multiple languages


	Communicating with message-oriented middleware
	Point-to-point domain
	Publish/subscribe domain


	XML
	Platform independent
	A number of standard tags have been developed to facilitate the transfer of information between companies


	<%@ page language="java" %>
	<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
	<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
	<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
	<html>
	<head>
	<title>Submit example</title>
	</head>


	<body>
	<h3>Example Submit Page</h3>
	<html:errors/>
	<html:form action="submit.do"> Last Name: <html:text property="lastName"/>
	<br> Address: <html:textarea property="address"/>
	<br> Sex: <html:radio property="sex" value="M"/>Male <html:radio property="sex" value="F"/>Female
	<br> Married: <html:checkbox property="married"/>
	<br> Age: <html:select property="age"> <html:option value="a">0-19</html:option> <html:option value="b">20-49</html:option> <html:option value="c">50-</html:option> </html:select>
	<br> <html:submit/> </html:form> </body> </html>


	This is the so-called “middleware”
	Comparable to the Microsoft Transaction Server and components
	The “application server” provides/ or is a bean container


	The J2EE security model lets you configure a Web component or
	enterprise bean so that system resources are accessed only by
	authorized users.
	The J2EE transaction model lets you specify relationships among
	methods that make up a single transaction so that all methods in one
	transaction are treated as a single unit.
	JNDI lookup services provide a unified interface to multiple naming
	and directory services in the enterprise so that application
	components can access naming and directory services.
	The J2EE remote connectivity model manages low-level
	communications between clients and enterprise beans. After an
	enterprise bean is created, a client invokes methods on it as if it were
	in the same virtual machine.


	Any good database software supports a transaction model that provides
		Read/write
		Commit
		Rollback
	EJB uses Java SQL to talk to database
	Database handles the actions
	Trade-off: how often is data committed?


	One bean asks whether a certain item is available. While that user makes up his mind, another bean asks the same question and quickly buys the bean. The first bean assumes that the item is still available and marks it as sold.
	EJB has locking capability. Can block access by others until commit or rollback ends the transaction


	Beans
		can not create threads
		Can not access threads with java.io
		Can not operate directly on sockets
		Can not use AWT to interact with user
		Only use parameter types allowed by RMI
		Must supply a no argument constructor


	CMP – container managed persistence
		Beans are portable
		Caching happens at an aggregated level
	BMP – bean managed persistence
		Beans are not as portable
		Caching is local


	An EJB is a set of Java classes and an XML file
	XML manifest locates resources that the bean will need
	Specifies services that the bean offers