Http:// Copyright © 2002 Qusay H. Mahmoud1 Developing Enterprise Applications Using Java School of Technology of Setubal Setubal, Portugal

http://www.javacourses.com Copyright © 2002 Qusay H. Mahmoud 1

Developing Enterprise Applications Using Java

School of Technology of Setubal

Setubal, PortugalApril 8, 2002

Qusay H. MahmoudSchool of Computing Science

Simon Fraser University, Vancouver, B.C., Canada

[email protected]


Objectives

Understand the architecture of the J2EEUnderstand the technologies involved

in J2EEKnow how to build web-based

enterprise applicationsKnow what effort is involved in

development


Agenda

The J2EE Platform and SDKThe J2EE APIsWeb Components (Servlets, JSPs)Enterprise JavaBeans Technology (EJBs)Duke’s Bank ApplicationSecurity issuesWeb ServicesOnline Resources


Enterprise Applications

Enterprise is a synonym for distributedDistributed computation done by programs

interacting over the networkEnterprise is a hot buzzwordReputation for complexityEnterprise computing takes place in a

heterogeneous networkInvolve the use of many different network

protocols


Buzzword: N-tier apps

Used to describe applications that reside on client and several servers


Why Java?

It helps alleviate intimidating aspects of enterprise computing Java is portable (Write Once, Run

Everywhere) Enterprise APIs form a single standard

layer on top of various proprietary or vendor-enhanced APIs

The elegance of Java and OO power make the APIs simpler, easier to understand, and easier to use


Java Platforms

[Source: Sun Microsystems Website]


J2EE Platform

Brings the benefits of component-based development to enterprise applications

Components are Simpler to develop Portable Reusable


J2EE Components

Server-side components Enterprise JavaBeans (EJBs) Java Servlets JavaServer Pages (JSPs)

Client-side components Application client

Configured via deployment descriptorsDeployed into containers


J2EE Components packed into Modules

Enterprise Beans (JAR file) Classes Deployment descriptor

Web Components (WAR file) Servlet classes, JSPs, HTML, images Web application deployment descriptor

Application Clients Classes Application client deployment descriptor


J2EE Applications

Packed into Enterprise ARchives (EAR file)Configured via application deployment

descriptors<application> <display-name>BankApp</display-name> <module> <ejb>account-ejb.jar</ejb> </module> … <module> <web> <web-uri>bank.war</web-uri> <context-root>bank</context-root> </web> </module></application>


J2EE Standard APIs

JDBCJava Naming and Directory Interface (JNDI)Java Message Service (JMS)Remote Method Invocation (RMI)Enterprise JavaBeans (EJBs)Technologies

Servlets JavaServer Pages (JSPs)


Other J2EE APIs

J2EE ConnectorsJava Transaction API (JTA)JavaIDLRMI-IIOPJava Transaction Service (JTS)JavaMail


Multi-tiered Architecture

Advantages: Decouples accessing of data from end-user

applications Encourages component-based code reusability


J2EE SDK

J2EE ServerCloudscape databaseApplication deployment tool

Create and edit deployment descriptors Package components and J2EE applications Verify and deploy J2EE applications

Download: http://java.sun.com/j2ee/download.html


J2EE SDK Tools

j2eeadmin: add/remove resourcescleanup: remove deployed apps from servercloudscape: start/stop/query database serverdeploytool: deploy/undeploy applications j2ee: start/stop J2EE serverkeytool: create keys and generate certificatespackager: package J2EE componentsrealmtool: add/remove J2EE users and import

certificatesverifier: validate J2EE archive files


J2EE Server

Standard containers (EJBs and Web) Life cycle management Concurrent execution

Standard platform services Security Transactions Resource connections


J2EE Containers

A container is the interface between a component and the low-level platform specific functionality

J2EE server provides services in the form of a container for every component type

You don’t have to develop these services yourself; you concentrate on solving the business problem


J2EE Containers

Before a component can be executed, it must be assembled into a J2EE application and deployed into its container


Web Components

Used to generate dynamic Web contentRun on the server-sidePortableReusableThey can be:

Based on the Java Servlet API Based on the JavaServer Pages (JSPs)


HTTP Overview

An application-level protocolSupports several request methods

( such as GET and POST) GET http://www.yahoo.com HTTP/1.0

Request

Reply


Servlets

A servlet is a Java classFunctions:

Process requests Create replies

Deployed into a Web container, which Manages servlet life cycle Maps URLs to servlets Converts HTTP requests and responses to objects


Servlet Example

A simple servletpublic class HelloServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{ response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println(“<html><head><title>hello</title></head>

"); out.println(<body><h1>Hello</h1></body></html>);}


Servlet as a Mediator

Devices that have no support for socket or datagram connections, access ‘net services through a mediator


JavaServer Pages (JSPs)

JSP is a document that contains two types of text Template data (HTML, XML, WML) that

generates static content JSP elements that generate dynamic content

Delegates dynamic processing to EJBs, JavaBeans components, custom tags

Translates into and executes as a servlet


JSP Elements

Directive controls translation into servlet class <%@ page import=“java.io.*” %>

Declaration creates object or method <%! int i %>

Scriptlet for dynamic processing <% ArrayList accts =

beanManager.getAcountController().getAccountsOfCustomer(request.getRemoteUser()); %>


JSP: JavaBeans Components

Create components and access their properties <jsp:useBean id=“accountHistBean” class=“AccountHistorybean”

scope=“request”/> scope: page, request, session, or application <jsp:setProperty name=“accountHistbean”

property=“beanManager” value=“<%= beanManager %>” />value can be a String or a JSP expression

<jsp:getProperty name=“accountHistBean” property=“credits” />


JSP: Custom Tags

Extensions to JSP that encapsulate dynamic processing

Tag libraries Standard Tag Library (JSR 052) Struts: http://jakarta.apache.org/struts Jakarta Taglibs: http://jakarta.apache.org/taglibs

Examples (we will see them in action) Effort involved in developing custom tags


Enterprise JavaBeans

What is an Enterprise Bean?

Component for EJB technology Runs on the server Encapsulates business logic Portable Reusable Transactional


How do Enterprise beans simplify development

Enterprise bean developer Focuses on solving business problems

EJB container Provides system-level services

Client developer Focuses on presentation and usability


Type of Enterprise Beans

Session beans

Entity beans

Message-driven beans


What is a Session Bean?

Represents a single client in the serverA logical extension of the clientTransient state – not persistent

Examples Sample session beans in action


What is an Entity Bean?

Represents a business object in a persistent storage (e.g. a database)

Often provides an object view of a database table

Examples Sample entity beans in action


What is a Message-Driven Bean?

Based on Java Message Service (JMS) technology)

Message listenerConsumes messages from a queueThe onMessage() method is invoked

upon message arrival


Structure of an EJB

Enterprise Bean Class Implementation

Home Interface Life cycle methods

Remote Interface Business methods

Deployment Descriptor XML file


Duke’s Bank Application

Online access to bank accountsCustomers – web clients

Withdraw and deposit funds Account history Transfer funds

Administrators (J2EE application client) Manage customers Manage accounts



High-level architecture

[source: Sun Microsystems Website]


Duke’s Bank Client’s View

Defining client’s view with interfaces



Enterprise Beans


Duke’s Client Application

Client: locate, create, deposit



TxControllerEJB: Deposit



TxEJB: Create



Web Component Integration

[source: Sun]



Security

Secure each container to secure entire application

Use authentication to prove identity Use authorization to restrict access


Application Client Security

Admin uses the application client to create customers and accounts

Must authenticate to access any management functions by the application client Login screen pops up when the application

client is accessed



Creating a customer account Admin creates the customer record

Customer ID is embedded in the customer record

Admin uses realmtool to add customer ID, password, group to default realmRealm –add 200 j2ee customer



Creating an account Admin accesses the application client and

creates an account for the customer Create methods in the enterprise bean can

only be accessed by users in the admin role

The customer ID, found in the customer record, binds the account to the customer



Securing the Web Components Web components are protected when the

application is deployed Customer must authenticate to access web

componentsA form-based login pops up when the customer tries to

access web component

Web component retrieves the customer ID by calling getUserPrincipal()

<% ArrayList accts = beanManager.getAccountController().getAccountsOfCustomer(request.getUserPrincipal().getName()); %>



Securing the Enterprise Beans Enterprise beans provide methods for creating

customer and accounts Method permissions on the home interface restrict

account and customer creation to admin role Roles and mapping between users and roles is

specified at application deployment time Enterprise beans provide methods for crediting,

debiting, transferring funds Methods permission on the remote interface

restricts these operations to customer role


Transaction Management

Indivisible unit of workAtomic (all or nothing)

Committed or rolled backBean-managed

Your code sets transaction boundariesContainer-managed

EJB container sets boundaries


Resources Connections

Types: Database connections Java Message Service API-based objects Mail sessions URLs Resource adapters


Resource Connections

Exampleprivate String dbName =

“java:comp/env/jdbc/BankDB”;

InitialContext ic = new InitialContext();

DataSource ds = (DataSource) ic.lookup(dbName);

Connection con = ds.getConnection();


Connector Architecture

Enables J2EE components such as EJB to interact with enterprise information systems

A resource adapter is a J2EE component that implements the J2EE connector architecture for a specific enterprise information system

A resource adapter is analogous to a JDBC driver For JDBC: the outside resource is DBMS For resource adapter: the outside resource is

enterprise information system


Web Services

Services offered through the web and can be accessed from any web-services enabled machine with Internet access


Online Resources

J2EE: http://java.sun.com/j2ee

J2EE Tutorial: http://java.sun.com/j2ee/tutorial

J2EE white papers:http://java.sun.com/j2ee/white

J2EE BluePrints:http://java.sun.com/blueprints


Online Resources

JSP Taglibs: http://java.sun.com/products/jsp/taglibraries.html

Tomcathttp://jakarta.apache.org/tomcat

Web Serviceshttp://java.sun.com/webservices

Deploying Web Services on J2EE:http://developer.java.sun.com/developer/technicalArticles/WebServices/wsj2ee


Thank you

Q & A


Copyright Info

Java™ and J2EE ™ are registered trademarks of Sun Microsystems, Inc.

Part of the slides have been adapted from J2EE Tutorial and JavaOne Sessions 2001.

All trademarked product and company names are the property of their respective trademark holders.


Speaker Bio

Qusay H. Mahmoud is a faculty member in the School of Computing Science at Simon Fraser University, Canada. He is widely published on the Java programming language, including the MIDP and Palm programming articles for Sun Microsystems Java Developer Connection. Qusay is the author of Distributed Programming with Java (Manning Publications, 1999) and Learning Wireless Java (O’Reilly & Associates, 2002)

http://www.cs.sfu.ca/~qmahmoud

Documents

Http:// Copyright © 2002 Qusay H. Mahmoud1 Developing Enterprise Applications Using Java School of Technology of Setubal Setubal, Portugal