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Developing Enterprise Applications
Using Java
School of Technology of Setubal
Setubal, Portugal
April 8, 2002
Qusay H. Mahmoud
School of Computing Science
Simon Fraser University, Vancouver, B.C., Canada
[email protected]
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
1
Objectives
Understand the architecture of the J2EE
Understand the technologies involved in
J2EE
Know how to build web-based enterprise
applications
Know what effort is involved in development
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
2
Agenda
The J2EE Platform and SDK
The J2EE APIs
Web Components (Servlets, JSPs)
Enterprise JavaBeans Technology (EJBs)
Duke’s Bank Application
Security issues
Web Services
Online Resources
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
3
Enterprise Applications
Enterprise is a synonym for distributed
Distributed computation done by programs
interacting over the network
Enterprise is a hot buzzword
Reputation for complexity
Enterprise computing takes place in a
heterogeneous network
Involve the use of many different network protocols
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4
Buzzword: N-tier apps
Used to describe applications that reside on
client and several servers
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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
http://www.javacourses.com
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6
Java Platforms
[Source: Sun Microsystems Website]
http://www.javacourses.com
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J2EE Platform
Brings the benefits of component-based
development to enterprise applications
Components are
Simpler to develop
Portable
Reusable
http://www.javacourses.com
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8
J2EE Components
Server-side components
Enterprise JavaBeans (EJBs)
Java Servlets
JavaServer Pages (JSPs)
Client-side components
Application client
Configured via deployment descriptors
Deployed into containers
http://www.javacourses.com
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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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
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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>
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11
J2EE Standard APIs
JDBC
Java Naming and Directory Interface (JNDI)
Java Message Service (JMS)
Remote Method Invocation (RMI)
Enterprise JavaBeans (EJBs)
Technologies
Servlets
JavaServer Pages (JSPs)
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
12
Other J2EE APIs
J2EE Connectors
Java Transaction API (JTA)
JavaIDL
RMI-IIOP
Java Transaction Service (JTS)
JavaMail
http://www.javacourses.com
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Multi-tiered Architecture
Advantages:
Decouples accessing of data from end-user applications
Encourages component-based code reusability
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J2EE SDK
J2EE Server
Cloudscape database
Application 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
http://www.javacourses.com
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J2EE SDK Tools
j2eeadmin: add/remove resources
cleanup: remove deployed apps from server
cloudscape: start/stop/query database server
deploytool: deploy/undeploy applications
j2ee: start/stop J2EE server
keytool: create keys and generate certificates
packager: package J2EE components
realmtool: add/remove J2EE users and import
certificates
verifier: validate J2EE archive files
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
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J2EE Server
Standard containers (EJBs and Web)
Life cycle management
Concurrent execution
Standard platform services
Security
Transactions
Resource connections
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
17
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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
18
J2EE Containers
Before a component can be executed, it
must be assembled into a J2EE application
and deployed into its container
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19
Web Components
Used to generate dynamic Web content
Run on the server-side
Portable
Reusable
They can be:
Based on the Java Servlet API
Based on the JavaServer Pages (JSPs)
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
20
HTTP Overview
An application-level protocol
Supports several request methods ( such as
GET and POST)
GET http://www.yahoo.com HTTP/1.0
Request
Reply
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Copyright © 2002 Qusay H. Mahmoud
21
Servlets
A servlet is a Java class
Functions:
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
http://www.javacourses.com
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22
Servlet Example
A simple servlet
public 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>);
}
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23
Servlet as a Mediator
Devices that have no support for socket or
datagram connections, access ‘net services
through a mediator
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24
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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
25
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().getAccountsOfCusto
mer(request.getRemoteUser()); %>
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Copyright © 2002 Qusay H. Mahmoud
26
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” />
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Copyright © 2002 Qusay H. Mahmoud
27
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
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28
Enterprise JavaBeans
What is an Enterprise Bean?
Component for EJB technology
Runs on the server
Encapsulates business logic
Portable
Reusable
Transactional
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
29
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
http://www.javacourses.com
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Type of Enterprise Beans
Session beans
Entity beans
Message-driven beans
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What is a Session Bean?
Represents a single client in the server
A logical extension of the client
Transient state – not persistent
Examples
Sample session beans in action
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
32
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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
33
What is a Message-Driven
Bean?
Based on Java Message Service (JMS)
technology)
Message listener
Consumes messages from a queue
The onMessage() method is invoked upon
message arrival
http://www.javacourses.com
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34
Structure of an EJB
Enterprise Bean Class
Implementation
Home Interface
Life cycle methods
Remote Interface
Business methods
Deployment Descriptor
XML file
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
35
Duke’s Bank Application
Online access to bank accounts
Customers – web clients
Withdraw and deposit funds
Account history
Transfer funds
Administrators (J2EE application client)
Manage customers
Manage accounts
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
36
Duke’s Bank Application
High-level architecture
[source: Sun Microsystems Website]
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
37
Duke’s Bank Client’s View
Defining client’s view with interfaces
http://www.javacourses.com
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Duke’s Bank Application
Enterprise Beans
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
39
Duke’s Client Application
Client: locate, create, deposit
http://www.javacourses.com
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Duke’s Bank Application
TxControllerEJB: Deposit
http://www.javacourses.com
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Duke’s Bank Application
TxEJB: Create
http://www.javacourses.com
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42
Duke’s Bank Application
Web Component Integration
[source: Sun]
http://www.javacourses.com
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43
Duke’s Bank Application
Security
Secure each container to secure entire
application
Use authentication to prove identity
Use authorization to restrict access
http://www.javacourses.com
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44
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
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Copyright © 2002 Qusay H. Mahmoud
45
Duke’s Bank Application
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 realm
Realm –add 200 j2ee customer
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
46
Duke’s Bank Application
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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
47
Duke’s Bank Application
Securing the Web Components
Web components are protected when the application is
deployed
Customer must authenticate to access web components
A 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().getAccountsOfCusto
mer(request.getUserPrincipal().getName()); %>
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
48
Duke’s Bank Application
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
http://www.javacourses.com
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49
Transaction Management
Indivisible unit of work
Atomic (all or nothing)
Committed or rolled back
Bean-managed
Your code sets transaction boundaries
Container-managed
EJB container sets boundaries
http://www.javacourses.com
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50
Resources Connections
Types:
Database connections
Java Message Service API-based objects
Mail sessions
URLs
Resource adapters
http://www.javacourses.com
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51
Resource Connections
Example
private String dbName =
“java:comp/env/jdbc/BankDB”;
InitialContext ic = new InitialContext();
DataSource ds = (DataSource) ic.lookup(dbName);
Connection con = ds.getConnection();
http://www.javacourses.com
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52
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
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
53
Web Services
Services offered through the web and can be
accessed from any web-services enabled
machine with Internet access
http://www.javacourses.com
Copyright © 2002 Qusay H. Mahmoud
54
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
http://www.javacourses.com
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55
Online Resources
JSP Taglibs:
http://java.sun.com/products/jsp/taglibraries.html
Tomcat
http://jakarta.apache.org/tomcat
Web Services
http://java.sun.com/webservices
Deploying Web Services on J2EE:
http://developer.java.sun.com/developer/tec
hnicalArticles/WebServices/wsj2ee
http://www.javacourses.com
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56
Thank you
Q&A
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57
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.
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58
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
http://www.javacourses.com
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59