J2EE

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J2EETM Platform Architecture

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Sang [email protected]

www.javapassion.com/j2ee

Technology EvangelistSun Microsystems, Inc.

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Courses I teach? XML (2001)? Distributed programming using JiniTM and

JavaSpacesT M technology (2002)? Web services programming using XML and JavaTM

technology (2002)? J2EETM programming with Passion! (It is free!)

www.javapassion.com/j2ee? Advanced J2EE programming with Passion! (It is

free!)

www.javapassion.com/j2eeadvanced4

Agenda ? What is J2EE? ? History of Distributed Computing ? Evolution of Enterprise Application

Development Frameworks ? J2EE APIs and Technologies

– Servlet, JSP, EJB, Connector, J2EE Security? RI, Compatibility Test Suite (CTS)? J2EE and Web Services? How to get started with J2EE programming? Web application framework

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What is J2EE?

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ChallengesPortabilityDiverse EnvironmentsTime-to-marketCore CompetenceAssemblyIntegration

Key Technologie

s

J2SE™

J2EE™

JMS

Servlet

JSPConnector

XML

Data BindingXSLT

Products

App Servers

Web Servers

Components Databases

Object to DB tools

LegacySystems

DatabasesTP Monitors

EIS Systems

Enterprise Computing

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What Is the J2EE?

l Open and standard based platform forl developing, deploying and managing l n-tier, Web-enabled, server-centric, and

component-based enterprise applications

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The Java™ 2 Platform

High-EndServer

Java TechnologyEnabled Desktop

WorkgroupServer

Java TechnologyEnabled Devices

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The JavaTM 2 Platform

OptionalPackages

Java 2Enterprise

Edition(J2EE)

Java 2StandardEdition(J2SE)

JVM

Java Card APIs

CardVM

OptionalPackages

Personal Basis Profile

PersonalProfile

Foundation Profile

CDC

MIDP

CLDC

KVM

Java 2 Platform Micro Edition(J2METM )

* Under development in JCP10

What Do You Get from J2EE?? API and Technology specifications? Development and Deployment Platform? Reference implementation ? Compatibility Test Suite (CTS)? J2EE brand? J2EE BluePrints

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History of Distributed Computing

Platform EvolutionCatchCatchPhrasePhrase

The NetworkThe NetworkIs the ComputerIs the Computer

ObjectsObjectsLegacy to Legacy to the Webthe Web

The Computer The Computer Is theIs the

NetworkNetwork

Network of Network of Embedded Embedded

ThingsThingsNetworkNetworkof Thingsof Things

ScaleScale

When/PeakWhen/Peak

LeafLeafProtocol(s)Protocol(s)

Directory(s)Directory(s)

SessionSession

100s100s 1,000s1,000s 1,000,000s1,000,000s 10,000,000s10,000,000s 100,000,000s100,000,000s 100,000,000s100,000,000s

1984/19871984/1987 1990/19931990/1993 1996/19991996/1999 2001/20032001/2003 1998/20041998/2004 2004/20072004/2007

XX XX +HTTP+HTTP(+JVM)(+JVM)

+XML+XMLPortalPortal +RM+RM UnknownUnknown

NS, NS+NS, NS+ +CDS+CDS +LDAP(*)+LDAP(*) +UDDI+UDDI +Jini+Jini +?+?

RPC, XDRRPC, XDR +CORBA+CORBA +CORBA,+CORBA,RMRM

+SOAP,+SOAP,XMLXML +RM/Jini+RM/Jini +?+?

SchematicSchematic

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Communication Patterns

Client-Server 3-Tier

Web Application

Web Services

HybridP2P Fractal

Communication Patterns: JavaTM 2

Business SystemsBusiness Systems

DB ServerDB Server

App ServerApp Server

Web ServerWeb Server

BrowserBrowserClientClient

Web Application

J2EEJ2EE

J2SE/J2SE/J2MEJ2ME

Communication Patterns: Sun ONE

Bus.Bus.Sys.Sys.

DBDB

AppApp

WebWeb

BrowserBrowser

Context and IdentityContext and Identity(LDAP, Policy, Liberty)(LDAP, Policy, Liberty)

J2EEJ2EE

J2SE/J2SE/J2MEJ2ME

XMLXML(UDDI, (UDDI, SOAP)SOAP)

Web Service

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Evolution ofEnterprise Application

Frameworks

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Evolution of Enterprise Application Framework

? Single tier ? Two tier? Three tier

– RPC based

– Remote object based

? Three tier (HTML browser and Web server)? Proprietary app server? Standard app server

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Single Tier (Mainframe-based)

? Centralized model (as opposed distributed model)

? Dumb terminals are directly connected to mainframe

? Presentation, business logic, and data access are intertwined in one monolithic mainframe application

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Single-Tier: Pros & Cons? Pros:

– No client side management is required

– Data consistency is easy to achieve

? Cons:– Functionality (presentation, data model, business logic)

intertwined, difficult for updates and maintenance and code reuse

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Two-Tier

? Fat clients talking to backend database– SQL queries sent, raw data returned

? Presentation,Business logic and Data Model processing logic in client application

Database

SQL request

SQL response

SQL request

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Two-Tier? Pro:

– DB product independence (compared to single-tier model)

? Cons:– Presentation, data model, business logic are intertwined

(at client side), difficult for updates and maintenance

– Data Model is “tightly coupled” to every client: If DB Schema changes, all clients break

– Updates have to be deployed to all clients making System maintenance nightmare

– DB connection for every client, thus difficult to scale

– Raw data transferred to client for processing causes high network traffic 22

Three-Tier (RPC based)

? Thinner client: business & data model separated from presentation

– Business logic and data access logic reside in middle tier server while client handles presentation

? Middle tier server is now required to handle system services

– Concurrency control, threading, transaction, security, persistence, multiplexing, performance, etc.

Database

SQL request

SQL responseRPC response

RPC request

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Three-tier (RPC based): Pros & Cons? Pro:

– Business logic can change more flexibly than 2-tier model

? Most business logic reside in the middle-tier server

? Cons:– Complexity is introduced in the middle-tier server

– Client and middle-tier server is more tightly-coupled (than the three-tier object based model)

– Code is not really reusable (compared to object model based)

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Three-Tier (Remote Object based)

? Business logic and data model captured in objects– Business logic and data model are now described in

“abstraction” (interface language)? Object models used: CORBA, RMI, DCOM

– Interface language in CORBA is IDL– Interface language in RMI is Java interface

Database

SQL request

SQL responseObject response

Object request

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Three-tier (Remote Object based): Pros & Cons

? Pro:– More loosely coupled than RPC model

– Code could be more reusable

? Cons:– Complexity in the middle-tier still need to be

addressed

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Three-tier (Web Server based): Pros & Cons? Pro:

– Ubiquitous client types

– Zero client management

– Support various client devices? J2ME-enabled cell-phones

? Cons:– Complexity in the middle-tier still need to be

addressed

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Trends

? Moving from single-tier or two-tier to multi-tier architecture

? Moving from monolithic model to object-based application model

? Moving from application-based client to HTML-based client

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Multi-tier

Single-tier vs. Multi-tier

l No separation among presentation, business logic, database

l Hard to maintain

l Separation among presentation, business logic, database

l More flexible to change, i.e. presentation can change without affecting other tiers

Single tier

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Object-based

Monolithic vs. Object-based

l 1 Binary filel Recompiled,

relinked, redeployed everytime there is a change

l Pluggable partsl Reusablel Enables better

designl Easier updatel Implementation

can be separated from interface

l Only interface is published

Monolithic

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Outstanding Issues & Solution? Comlexity at the middle tier server still remains? Duplicate system services still need to be

provided for the majority of enterprise applications

– Concurrency control, Transactions– Load-balancing, Security– Resource management, Connection pooling

? How to solve this problem? – Commonly shared container that handles the above

system services

– Proprietary versus Open-standard based32

Proprietary Solution? Use "component and container" model in

which container provides system services in a well-defined but with proprietary manner

? Problem of proprietary solution: Vendor lock-in

? Example: Tuxedo, .NET

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Open and Standard Solution? Use "component and container" model in

which container provides system services in a well-defined and as industry standard

? J2EE is that standard that also provides portability of code because it is based on Java technology and standard-based Java programming APIs

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Why J2EE?

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Platform Value to Developers? Can use any J2EE implementation for

development and deployment – Use J2EE RI or Sun ONE Platform Edition which are

free for development/deployment and then use high-end commercial J2EE products for actual deployment

? Vast amount of J2EE community resources– Many J2EE related books, articles, tutorials, quality

code you can use, best practice guidelines, design patterns etc.

? Can use off-the-shelf 3rd-party business components 36

Platform Value to Vendors? Vendors work together on specifications and

then compete in implementations– In the areas of Scalability, Performance, Reliability,

Availability, Management and development tools, and so on

? Freedom to innovate while maintaining the portability of applications

? Do not have create/maintain their own proprietary APIs

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Platform Value to Business Customers? Application portability ? Many implementation choices are possible

based on various requirements– Price (free to high-end), scalability (single CPU to

clustered model), reliability, performance, tools, and more

– Best of breed of applications and platforms

? Large developer pool

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J2EE API's &Technologies

(page 14, 1st slide)

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J2EE 1.3 APIs and Technologies

Java 2 SDK, Standard EditionRMI/ IIOP

JDBC™ Java Messaging Service

JNDIServlet

JavaServer Pages™JavaMail

JavaBeans™ Activation FrameworkEnterprise JavaBeansJava Transaction API

Java Transaction ServiceConnector Architecture

ECPerf™

Version1.31.03.0

1.0.2b 1.2.1

2.31.21.2

1.0.12.0

1.0.11.11.01.0

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J2EE 1.4 Contents? J2SE 1.4 (improved)? JAX-RPC (new)? Web Service for J2EE? J2EE Management? J2EE Deployment? JMX 1.1? JMS 1.1? JTA 1.0

? Servlet 2.4? JSP 2.0? EJB 2.1? JAXR? Connector 1.5? JACC? JAXP 1.2? JavaMail 1.3? JAF 1.0

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Servlet

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What is a Servlet?

? Java™ objects which extend the functionality of a HTTP server

? Dynamic contents generation? Better alternative to CGI, NSAPI, ISAPI, etc.

– Efficient– Platform and server independent

– Session management

– Java-based

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Servlet

CGI versus Servlet

l Written in C, C++, Visual Basic and Perl

l Difficult to maintain, non-scalable, non-manageable

l Prone to security problems of programming language

l Resource intensive and inefficient

l Platform and application-specific

l Written in Javal Powerful, reliable, and

efficientl Improves scalability,

reusability (component based)

l Leverages build-in security of Java programming language

l Platform independent and portable

CGI

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Servlet vs. CGI

CGIBased

Webserver

CGIBased

Webserver

Request CGI1Child for CGI1

CGIBased

Webserver

Servlet Based Webserver

JVM


Request Servlet1

CGIBased

Webserver


JVMServlet1


Request CGI2

Request Servlet1

CGIBased

WebserverChild for CGI2


JVMServlet1


Request CGI2

Request Servlet1

Request Servlet2

CGIBased



JVMServlet1

Servlet2


Request CGI2

Request CGI1

Request Servlet1

Request Servlet2

CGIBased


Child for CGI1


JVMServlet1

Servlet2


Request CGI2

Request CGI1

Request Servlet1

Request Servlet2

Request Servlet1

CGIBased


Child for CGI1


JVMServlet1

Servlet2


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Servlets Request and Response

Servlet

Response

Request

BrowserHTTP

WebWebServerServer

Servlet Container

Response

Request

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What does Servlet Do?? Receives client request (mostly in the form

of HTTP request)? Extract some information from the request? Do content generation or business logic

process (possibly by accessing database, invoking EJBs, etc)

? Create and send response to client (mostly in the form of HTTP response) or forward the request to another servlet

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Requests and Responses? What is a request?

– Information that is sent from client to a server? Who made the request? What user-entered data is sent? Which HTTP headers are sent

? What is a response? – Information that is sent to client from a server

? Text(html, plain) or binary(image) data? HTTP headers, cookies, etc

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HTTP GET and POST? The most common client requests

– HTTP GET & HTTP POST

? GET requests:– User entered information is appended to the URL in a

query string

– Can only send limited amount of data? .../servlet/ViewCourse?FirstName=Sang&LastName=Shin

? POST requests:– User entered information is sent as data (not appended

to URL)– Can send any amount of data

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First Servlet import javax.servlet.*;import javax.servlet.http.*;import java.io.*;

Public class HelloServlet extends HttpServlet { public void doGet(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<title>First Servlet</title>"); out.println("<big>Hello Code Camp!</big>"); }}

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Session Tracking

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Why Session Tracking?? Need a mechanism to maintain state

across a series of requests from the same user (or originating from the same browser) over some period of time

– Example: Online shopping cart

? Yet, HTTP is stateless protocol– Each time, a client talks to a web server, it opens

a new connection

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Session Tracking Use Cases

? When clients at an online store add an item to their shopping cart, how does the server know what’s already in the cart?

? When clients decide to proceed to checkout, how can the server determine which previously created shopping cart is theirs?

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Sessions

Session 1

Session 2

Client 1

Client 2

serverSession ID 1

Session ID 2

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Three Session Tracking Mechanisms? Cookies? URL rewriting? Hidden form fields? Note that these are just underlying

mechanisms and do not provide high-level programming APIs

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What is Cookie?? Cookie is a small amount of information sent

by a servlet to a Web browser? Saved by the browser, and later sent back to

the server in subsequent requests? A cookie's value can uniquely identify a client

– So cookies are commonly used for session management

? A cookie has a name, a single value, and optional attributes

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Cookies as Session Tracking

? Advantages:– Very easy to implement

– Highly customizable

– Persist across browser shut-downs

? Disadvantages:– Often: users turn off cookies for privacy or

security reason

– Not quite universal browser support

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URL Rewriting? URLs can be rewritten or encoded to include

session information.? URL rewriting usually includes a session id? Session id can be sent as an added

parameter:– http://.../servlet/Rewritten?sessionid=688

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URL Rewriting as Session Tracking Mechanism ? Advantages:

– Let user remain anonymous

– They are universally supported(most styles)

? Disadvantages:– Tedious to rewrite all URLs

– Only works for dynamically created documents

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Now Without “Session Tracking” Feature of Servlet

? You have to perform the following tasks yourself by using one of three session-tracking mechanisms

– Generating and maintaining a session id for each session

– Passing session id to client via either cookie or URL

– Extracting session id information either from cookie or URL

– Creating and maintaining a hashtable in which session id and session information are stored

– Coming up with a scheme in which session information can be added or removed

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“ Session Tracking” Feature of Servlet

? Provides higher-level API for session tracking

– Built on top of Cookie or URL rewriting

? Servlet container maintains

– internal hashtable of session id's

– session information in the form of HttpSession? Generates and maintains session id transparently? Provides a simple API for adding and removing

session information (attributes) to HttpSession? Could automatically switch to URL rewriting if

cookies are unsupported or explicitly disabled

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What are Java Servlet Filters?? New component framework for intercepting

and modifying requests and responses– Filters can be chained and plugged in to the system

during deployment time

? Allows range of custom activities:– Marking access, blocking access

– Caching, compression, logging

– Authentication, access control, encryption

– Content transformations

? Introduced in Servlet 2.3 (Tomcat 4.0)62

What Can a Filter Do?? Examine the request headers? Customize the request object if it wishes to

modify request headers or data? Customize the response object if it wishes to

modify response headers or data? Invoke the next entity in the filter chain? Examine response headers after it has invoked

the next filter in the chain? Throw an exception to indicate an error in

processing

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How Servlet Filter Work?

Filter 2

ServletContainer

Filter NFilter 1

ServletFilter Chain

Userimplementedfilters

Servletcontainerfilter

doFilter(ServletRequest,ServletResponse,FilterChain)

service(ServletRequest,ServletResponse) 64

JSP

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What is JSP Technology?? Enables separation of business logic from

presentation– Presentation is in the form of HTML or

XML/XSLT

– Business logic is implemented as Java Beans or custom tags

– Better maintainability, reusability

? Extensible via custom tags? Builds on Servlet technology

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What is JSP page?

? A text-based document capable of returning dynamic content to a client browser

? Contains both static and dynamic content

– Static content: HTML, XML

– Dynamic content: programming code, and JavaBeans, custom tags

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JSP Sample Code<html> Hello World!<br><jsp:useBean id="clock" class=“calendar.JspCalendar” /> Today is<ul><li>Day of month: <%= clock.getDayOfMonth() %><li>Year: <%= clock.getYear() %></ul>

</html>

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JSP

Servlets and JSP - Comparison

• HTML code in Java• Any form of Data• Not easy to author a

web page

• Java-like code in HTML• Structured Text• Very easy to author a

web page• Code is compiled into a

servlet

Servlets

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JSP Benefits? Content and display logic are separated? Simplify development with JSP, JavaBeans

and custom tags? Supports software reuse through the use of

components? Recompile automatically when changes are

made to the source file? Easier to author web pages? Platform-independent

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Web-Tier Security Issues

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General Security Issues ? Authentication for identity verification

– Making sure a user is who he claims he is

? Authorization (Access control)– Making sure a resource gets access only by user who

as access priviledge

– The user has to be authenticated first

? Confidentiality (Privacy)– Making sure nobody can read the sensitive data

while it is on the wire

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Security Issues at Web-Tier? Preventing unauthorized users from

accessing “access controlled” web resource– If unauthenticated user tries to access “access

controlled” web resource, web container will automatically ask the user to authenticate himself first

– Once authenticated, web container (and/or web components) enforces access control

? Preventing attackers from changing or reading sensitive data while it is on the wire

– Data can be protected via SSL

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HTTP BasicAuthentication-

basedWeb tier Security

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HTTP Basic Authentication ? Web server collects user identification (user

name and password) through a browser provided dialog box

? Not secure since user name and password are in “easily decode'able” form over the wire

– Encoding scheme is Base64– Someone can easily decode it – Not encrypted

? Would need SSL for encrypting password

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Steps for Basic Authentication-based Web-tier Security 1.Set up username, passwords, and roles

(realms)

2.Tell web container that you are using Basic authentication

3.Specify which URLs (web resources) should be access-controlled (password-protected)

4.Specify which URLs should be available only with SSL (data integrity and confidentiality protected)

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Step 1: Set up username, passwords, and roles (Realms)

? Schemes, APIs, and tools for setting up usernames, passwords, and roles (realms) are web container and operational environment specific

– Flat-file based, Database, LDAP server– Passwords could in encrypted or unencrypted form

? Tomcat 4.0 can work with the following realms– default: file, unencrypted form

– Relational database (via JDBCRealm)– LDAP server (via LDAPRealm)

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Example: Tomcat's default? <install-dir>/config/tomcat-users.xml? Unencrypted: not secure but easy to set up

and maintain

<?xml version='1.0'?><tomcat-users> <role rolename="manager"/> <role rolename="employee"/> <role rolename="admin"/> <user username="sang" password="sangPassword"

roles="manager,employee"/></tomcat-users>

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Step 2: Tell web container that you are using Basic authentication? In web.xml file of your web application

<web-app> ... <security-constraint>...</security-constraint> <login-config> <auth-method>BASIC</auth-method> <realm-name>realm name</realm-name> </login-config> ... </web-app>

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Step 3: Specify which URLs should be access-controlled <web-app> ... <security-constraint> <web-resource-collection> <web-resource-name>WRCollection</web-resource-name> <url-pattern>/loadpricelist</url-pattern> <http-method>GET</http-method> </web-resource-collection> <auth-constraint> <role-name>admin</role-name> </auth-constraint> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint> <login-config> <auth-method>BASIC</auth-method> <realm-name></realm-name> </login-config> ...</web-app> 80

Step 4: Specify which URLs should be available only with SSL <web-app> ... <security-constraint> <web-resource-collection> <web-resource-name>WRCollection</web-resource-name> <url-pattern>/loadpricelist</url-pattern> <http-method>GET</http-method> </web-resource-collection> <auth-constraint> <role-name>admin</role-name> </auth-constraint> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint> <login-config> <auth-method>BASIC</auth-method> <realm-name></realm-name> </login-config> ...</web-app>

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Form-based Authentication

basedWeb-tier Security

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Form-based Authentication ? Web application collects user identification

(user name, password, and other information) through a custom login page

? Not secure since user name and password are in “easily decode'able” form over the wire

– Encoding scheme is Base64– Someone can easily decode it – Not encrypted

? Would need SSL for encrypting password

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Steps for Form-based Authentication based Web-tier Security

1.Set up username, passwords, and roles (realms)

2.Tell web container that you are using Form-based authentication

3.Create Login page

4.Create Login failure error page

5.Specify which URLs (web resources) should be access-controlled (password-protected)

6.Specify which URLs should be available only with SSL (data integrity and confidentiality protected)

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Step 1: Set up username, passwords, and roles (Realms) ? Same as in Basic-authentication

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Step 2: Tell web container that you are using Form-based authentication

? In web.xml file of your web application<web-app> ... <security-constraint>...</security-constraint> <login-config> <auth-method>FORM</auth-method> <realm-name>realm name</realm-name> </login-config> ... </web-app>

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Step 3: Create Login Page

? Can be HTML or JSP page? Contains HTML form like following

<FORM ACTION="j_security_check" METHOD="POST"> … <INPUT TYPE="TEXT" NAME="j_username"> … <INPUT TYPE="PASSWORD" NAME="j_password"> …</FORM>

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Step 4: Create Login Failure page

? Can be HTML or JSP page? No specific content is mandated

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Step 5: Specify which URLs should be access-controlled (Same as Basic Auth)<web-app> ... <security-constraint> <web-resource-collection> <web-resource-name>WRCollection</web-resource-name> <url-pattern>/loadpricelist</url-pattern> <http-method>GET</http-method> </web-resource-collection> <auth-constraint> <role-name>admin</role-name> <role-name>executive</role-name> </auth-constraint> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint> <login-config> <auth-method>FORM</auth-method> <realm-name></realm-name> </login-config> ...</web-app> 90

Step 6: Specify which URLs should be available only with SSL (Same as Basic Auth)<web-app> ... <security-constraint> <web-resource-collection> <web-resource-name>WRCollection</web-resource-name> <url-pattern>/loadpricelist</url-pattern> <http-method>GET</http-method> </web-resource-collection> <auth-constraint> <role-name>admin</role-name> </auth-constraint> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint> <login-config> <auth-method>FORM</auth-method> <realm-name></realm-name> </login-config> ...</web-app>

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Form-based

Basic vs. Form-based Authentication

• Uses “browser provided dialog box” to get username and password

• Only username and password can be collected

• Might result in different look and feel

• HTTP Authentication header is used to convey username and password

• No good way to enter a new user name

• Uses “web application provided login page” to get username and password

• Custom data can be collected

• Can enforce consistent look and feel

• Form data is used to convey username and password

• Can enter a new user name via login page

Basic

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EJB(Enterprise Java Beans)

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What is EJB Technology?? Cornerstone of J2EE? A server-side component technology ? Easy development and deployment of

Java technology-based application that are:

– Transactional, distributed, multi-tier, portable, scalable, secure, …

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Why EJB Technology?? Leverages the benefits of component-

model on the server side? Separates business logic from system code? Provides framework for portable

components– Over different J2EE-compliant servers

– Over different operational environments

? Enables deployment-time configuration– Deployment descriptor

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Do You Need an EJB Tier?? Yes, if you want to leverage middleware features

provided by container– Resource management, instance life-cycle

management, concurrency control and threading– Persistence, transaction and security management– Messaging, scalability, availability

? Yes, if you want to build portable and reusable business components

? Maybe not, for a simple application whose main function is reading database tables

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EJB Architecture

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EJB Architecture Contracts

? Contracts are specified in EJB specification? Client view contract

– Contract between client and container

? Component contract– Contract between an Enterprise Bean and its

Container

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Client View Contract

? Client of an EJB can be– Web tier components: Servlet and JSP

– Standalone Java application

– Applet

– Another EJB in same or different container

– Web services client (in EJB 2.1)

? Provides development model for clients using EJB services

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Client View Contract (Contd.)

? Client view contract is comprised of– Home interface

? For local or remote clients? Contains methods for creating and locating beans

– Remote interface? For local or remote clients? Contains business methods

– Object identity

– Metadata interface

– Handle100

Component Contract: What Container does (for Beans)? Enables EJB method invocations from clients? Manage the life cycle of EJB bean instances? Implements home and remote interfaces? Provide persistence for CMP entity beans? Provide runtime context information to beans? Manage transactions, security, exceptions, etc...? Implements callbacks

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EJB Contracts

ClientEnterprise

bean instances

EJBContainer

Component contract

EJB server

Client view contract

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Types of Beans

? Session Beans– Stateful session beans

– Stateless session beans

? Entity Beans– Bean Managed Persistence (BMP)

– Container Managed Persistence (CMP)

? Message Driven Beans– JMS

– JAXM

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Session Beans? Does work on behalf of a single client? Is not persistent and hence relatively short

lived– Is removed when the EJB™ server crashes

? Does not represent data in data store, although can access/update such data

? Bean class implements javax.ejb.SessionBean interface

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When to Use Session Beans?? Use Session beans to model process or control

objects specific to a particular client.

? To model workflow, processes or tasks, manage activities (make reservation, purchase...).

? To Coordinate processes between entity beans, control interactions of beans.

? To Move business application logic from Client to the Server Side.

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2 Types of Session Beans? Stateless: execute a request and return a

result without saving any client specific state information

– transient

– temporary piece of business logic needed by a specific client for a limited time span

? Stateful: maintains client specific state

State instance data

Stateful Session beanStateless Session bean

106

Examples of Session Beans

? Stateless session beans– Catalog

? No client specific state needs to be preserved

– Interest calculator? No client specific state needs to be preserved? Business logic with no need for database access

? Staeful session beans– Shopping cart

? Client specific state needs to be preserved

107

Entity Beans? Provides object view of data in data store

– Its lifetime not related to the duration of interaction with clients

– Lives as long as data exists in database i.e. Long lived

– In most cases, synchronized with relational databases

? Shared access among clients? Bean class implements

javax.ejb.EntityBean interface

108

Entity Beans? Clients normally look up (find) an existing

entity EJB– Creation means adding a row to a database table

– Finding means finding a row in a existing database table

? Entity bean instance has unique identifier called primary key

– Primary key can be any class

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Examples of Entity Beans? Customer

– Customer data has to persist, thus is maintained in the database

– Customer data has to survive server crash

– Customer data is shared by many clients

– Each customer has unique identification such as customer number

110

2 Types of Entity Beans? CMP (Container Managed Persistence)

– Persistence is managed by Container

– Persistence requirements are specified in deployment descriptor

– Bean developer does not have to worry about providing persistence logic in his code

? BMP (Bean Managed Persistence)– Persistence logic code is provided by Bean

developer

111

When to Use CMP vs. BMP?? CMP entity beans

– With CMP 2.0, there is no reason not to use CMP

– Database independence

– Higher performance

– Easy to develop and deploy

? BMP entity beans– More programmatic control is desired

112

Session Beans and Entity Beans

? Represent a business process

? One instance per client? Short-lived: Life of

client is life of bean? Transient? Doesn’t survive server

crashes? May be transactional

? Represent business data? Shared instance for

multiple clients? Long-lived: as long as

data in database? Persistent? Survive server crashes? Always transactional

Session Beans Entity Beans

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113

Entity and Session Beans—Typical Architecture

114

Entity and Session Beans

115

Message-Driven Beans (MDB)? Acts as a consumer of asynchronous

messages? Cannot be called directly by clients

– Activated upon message arrival

– No home or remote interface

? Clients interact with MDB by sending messages to the queues or topics to which they are listening

? Stateless

116

JMS(Java Message Service)

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Java Message Service (JMS) ? Messaging systems (MOM) provide

– Decoupled communication

– Asynchronous communication– Plays a role of centralized post office

? Benefits of Messaging systems– Flexible, Reliable, Scalable communication

systems

? Point-to-Point, Publish and Subscribe? JMS defines standard Java APIs to

messaging systems118

Connector Architecture

119

Connector Architecture ? Defines standard SPI for integrating J2EE

technology with EIS systems– CICS, SAP, PeopleSoft, etc.

? Before Connector architecture, each App server has to provide an proprietary adaptor for each EIS system

– m (# of App servers) x n (# of EIS'es) Adaptors

? With Connector architecture, same adaptor works with all J2EE compliant containers

– 1 (common to all App servers) x n (# of EIS'es) Adaptors 120

m x n Problem Before Connector Architecture

AppServer1

AppServer

AppServer3

AppServer2

SAP

EIS4

EIS3

m n

EIS2

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121

Connector Architecture ? Defines

– Connection pooling

– Security

– Transaction

122

Other J2EE APIs &Technologies

123

JNDI

? Java Naming and Directory Interface? Utilized by J2EE applications to locate

resources and objects in portable fashion– Applications use symbolic names to find object

references to resources via JNDI

– The symbolic names and object references have to be configured by system administrator

124

JDBC

? Provides standard Java programming API to relational database

– Uses SQL

? Vendors provide JDBC compliant driver which can be invoked via standard Java programming API

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125

J2EE Management (JSR-77)

? Management applications should be able to discover and interpret the managed data of any J2EE platform

? Single management platform can manage multiple J2EE servers from different vendors

? Management protocol specifications ensure a uniform view by SNMP and WBEM management stations

? Leverages JMX126

J2EE Management (JSR-77) - J2EE 1.4

? Management information model• example: J2EE app server, EJB beans

? Mapping the information model to• CIM (Common Information Model)

• SNMP MIB (Management Information Base)

• Java APIs for J2EE Management EJB component (MEJB)

• Exposes managed objects as JMX Managed Beans (Mbeans)

127

J2EE Deployment (JSR-88) - J2EE 1.4 Tools J2EE Platforms

StandardDeployment API

(Universal Remote)IDEs

Vendor Deploy Tools

Management Tools

128

J2EE App ServerApp

JMX

JMX

JMX de-facto

Dynamic DeploymentJMX API into the J2EE 1.4 platform

A single technology for the J2EE platform

JMX

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129

JACC (Java Authorization Contract for Containers) - J2EE 1.4

? Defines contract between J2EE containers and authorization policy modules

– Provider configuration subcontract

– Policy configuration subcontract

– Policy enforcement subcontract

? Enable application servers to integrate with enterprise user registries and authorization policy infrastructure

130

J2EE as End-to-EndArchitecture

131

The J2EE Platform Architecture

B2BApplications

B2CApplications

WebServices

WirelessApplications

Application ServerEnterprise

InformationSystems

ExistingApplications

132

Client

Client

Client

Client

Client

ClientTier

Enterprise Information

TierMiddle

Tier

Enterprise Information

Systems (EIS):RelationalDatabase,Legacy

Applications,

ERP Systems

Enterprise JavaBeans™

Enterprise JavaBeans

Other Services:JNDI, JMS,JavaMail™

J2EEApplication

Server

Web ServerJSP,

Servlets

Firewall

J2EE is End-to-End Solution

HTML/XML

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133

N-tier J2EE Architecture

Web Tier EJB Tier

134

J2EE Component & Container

Architecture

135

JND

I

J2SE

JM

S

RM

I/IIO

P

JDB

C

Database

AppClient

App Client Container

HTTP/HTTPS

J2SE

RMI

J2SE

JND

I

JMS

RM

I/IIO

P

JDB

C

JT

A JavaMail

JAF JND

I

JM

S

RM

I/IIO

P

JDB

C

JT

A JavaMail

JAF

HTTP/HTTPS

Applet Container

Applet JSP Servlet EJB

Web Container EJB Container

RMI

J2SE

J2EE Containers & Components

136

ComponentsHandle

Containers and Components

l Concurrencyl Securityl Availabilityl Scalabilityl Persistencel Transactionl Lifecycle

managementl Management

l Presentationl Business Logic

ContainersHandle

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137

Containers & Components

? Containers do their work invisibly

– No complicated APIs

– They control by interposition

? Containers implement J2EE– Look the same to components

– Have great freedom to innovate

138

J2EE ApplicationDevelopment & Deployment

Life Cycle

139

J2EE Application Development Lifecycle? Write and compile component code

– Servlet, JSP, EJB

? Write deployment descriptors for components

? Assemble components into ready-to-deploy'able package

? Deploy the package on a server

140

Creation Assembly Deployment

Created by Component Developer

Assembledand Augmentedby Application

Assembler

Processed by Deployer

Deploy

EnterpriseComponents

J2EE Container

J2EE APPJ2EE Modules

Lifecycle Illustration

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J2EE Roles? Component provider

– Bean provider

? Application assembler? Deployer? Platform provider

– Container provider

? Tools provider? System administrator

142

The Deployment Descriptor? Gives the container instructions on how to

manage and control behaviors of the J2EE components– Transaction

– Security

– Persistence? Allows declarative customization (as

opposed to programming customization)– XML file

? Enables portability of code

143

J2EE ApplicationAnatomies

144

DB & EISResources

Browser

Stand-alone

Web Server EJB Server

Web Server EJB Server

Possible J2EE Application Anatomies

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145

J2EE Application Anatomies

? 4-tier J2EE applications

– HTML client, JSP/Servlets, EJB, JDBC/Connector

? 3-tier J2EE applications– HTML client, JSP/Servlets, JDBC

? 3-tier J2EE applications

– EJB standalone applications, EJB, JDBC/Connector

? B2B Enterprise applications

– J2EE platform to J2EE platform through the exchange of JMS or XML-based messages

146

Which One to Use?? Depends on several factors

– Requirements of applications

– Availability of EJB tier

– Availability of developer resource

147

J2EE Reference Implementation,Compatibility Suite, Brand

148

What and Why a Reference Implementation?? Validates specification? Fully-compliant? Fully-functional? Not commercial quality

– Scalability– Performance

? Use it for prototyping? Java Web Services Developer Pack is

production quality, however

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149

Compatibility Test Suite (CTS)? Ultimate Java™ technology mission:

– Write Once, Run Anywhere™

– My Java-based application runs on any compatible Java virtual machines

– My J2EE based technology-based application will run on any J2EE based Compatible platforms

150

J2EE Application Verification Kit (J2EE AVK)? How can I test my J2EE application portability?

• Obtain the J2EE RI 1.3.1 and the J2EE Application Verification Kit (J2EE AVK)

? Self verification of application– Static verification

– Dynamic verification

? Obtain the tests results, verify that all criteria are met

151

Compatible Products for the J2EE Platform (Brand)

ATG

Bea Systems

BorlandComputer

Associates

FujitsuHitachi

HP

IBMIONA

iPlanet

Macromedia

NECOracle

Pramati

SilverStreamSybase

Talarian

Trifork

152

J2EE™ Technology LicenseesAOL

ATG

BEA Systems

HP Bluestone

BroadVision

Borland

Compaq

CA

Fujitsu

Gemstone

Hitachi

IBM

Interworld

In-Q-My

IONA

iPlanet

Lutris

Macromedia

NEC

Nokia

Merant

Oracle Corp.

Cape Clear

Persistence

Pramati

SAS Institute

Silverstream

Sonic

Sybase

Secant

SpiritSoft

Talarian

TIBCO

TMAX Soft

TogetherSoft

Trifork

WebGain

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153

The J2EE Platform “Ecosystem,”Application Servers and…? Tools

– IDE’s: Borland JBuilder Enterprise, WebGain Visual Cafe’, IBM Visual Age for Java™, Forte™ for Java™, Oracle JDeveloper, Macromedia Kawa

– Modeling, Performance, Testing, etc.

? Enterprise Integration: Connectors, Java Message Service (JMS) API, XML

? Components? Frameworks? Applications

154

Major Investment in Compatibility by the Industry? Sun has spent scores of engineer years

developing tests? Licensees have spent scores of engineer

years passing the tests? Testing investment on top of specification

investment, implementation investment, business investments

? In total, tens of millions of dollars invested in J2EE platform compatibility by the industry

155

J2EE Blueprint &Pet Store Application

156

J2EE BluePrint? Best practice guidelines, design patterns

and design principles– MVC pattern

? Covers all tiers– Client tier

– Web tier

– Business logic (EJB) tier

– Database access tier

? Sample code– Java Pet Store

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157

Web ServicesSupport in J2EE 1.4

158

J2EE 1.4 Theme ? Major theme is Web Services? Allow J2EE applications to be exposed as

SOAP/HTTP based Web services? Integrate with existing Web services? Ensure interoperability

• SOAPBuilder effort

• Will support WS-I Basic profile

159

Design Goals J2EE Web Services Framework

? Portability of Web services component

– Over different vendor platform

– Over different operational environment

? Leveraging existing J2EE programming models for service implementation

? Easy to program and deploy

– High-level Java APIs

– Use existing deployment model160

What Is a J2EE Web Service?? A set of endpoints (ports) operating on

messages? Ports are operating within a container

– Container provides runtime environment

– Contract for runtime environment are specified in JAX-RPC, EJB 2.1, JSR 109

? Service is described abstractly in WSDL document and published to a registry

– WSDL specifies a contract between service provider and client

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161

Web Service Component and Container

? Container vs. Component model

– Web services components get executed within a container

– Components are portable (under J2EE 1.4)

? Web service components

– Web-tier (Servlet-based endpoint)

– EJB-tier (Stateless session bean-based endpoint)

162

Web Service Components

Source: Web Services for J2EE (JSR 109), V1.0

Web services components

163

Java APIs forWeb Services over J2EE

164

Web Services for J2EE (JSR 109)? Addresses overall Web services architecture

over J2EE

– Deployment requirements for Web service clients and endpoints

– Standard deployment descriptors

– JAX-RPC programming model

– JNDI lookup of service objects

– Container-managed security

– Declaration of handlers and serializers

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165

JAX-RPC

? Servlet-based Web service endpoint model

? XML data types to/from Java types mapping

? WSDL to/from Java mapping

? JAX-RPC Client Programming Models

? SOAP Message Handler framework

? Extensible type mapping

166

JAX-RPC Architecture Diagram

Server-side JAX-RPCRuntime System

Container

JAX-RPCService Endpoint

WSDLóJava

WSDL Document

HTTP

Client-side JAX-RPCRuntime System

SOAP

Container

JavaïWSDLGenerated Code

JAX-RPC Client

167

Relationship to WSDL

JAX-RPC describes a Web Service as a collection of remote interfaces and methods

Tools are used to convert between WSDL documents and sets of Java remote interfaces (“Generate Web Services Files” menu in Sun ONE Studio 5, “wscompile” in Java WSDP)

WSDL describes a Web Service as a collection of ports and operations

168

SOAP Message Handlers? Handlers let you access/modify SOAP

request and response messages– Typically used to process service contexts in SOAP

header blocks

– Can be used to extend functionality of Web services runtime system

? J2EE containers (which provide Web services runtime) are likely to use them internally to provide session/transaction propagation

? Example handlers: – encryption, decryption, authentication,

authorization, logging, auditing, caching

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SOAP Message Handlers? Pluggable and chainable

– Through standardized programming API

– Portable across implementations

? Has its own lifecycle– JAX-RPC runtime system calls init(), destroy() of a

handler

? Handler instances can be pooled? MessageContext is used to share properties

among handlers in a handler chain

170

SOAP Message Handlers

Service Endpoint (Port)Handler Handler

SOAP Message<Request>

SOAP Message<Response>

Handler Chain

171

JAX-RPC Client Programming Models? Stub-based (least dynamic)

– Both interface (WSDL) and implementaion (stub) created at compile time

? Dynamic proxy– Interface (WSDL) created at compile time

– Implementation (dynamic proxy) created at runtime

? Dynamic invocation interface (DII)– Both interface (WSDL) and implementaion

created at runtime 172

Service Implementation

public class AttachmentServiceImpl extends AttachmentService {

public String storeImageService(DataHandler dh,

String imageFileName){

...

BufferedInputStream in =

new BufferedInputStream (dh.getInputStream());

...

}

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Client sending Attachmentpublic class AttachmentServiceClient {

public static void main(String[] args) { ...

DataHandler dh =

new DataHandler(new FileDataSource(filename));

AttachmentService myProxy = ...

String response = myProxy.storeImageService(dh, filename);

...

}

}

174

SAAJ

? Handles low-level SOAP message handling

• Contains the API for creating and populating a SOAP messages conforming to SOAP 1.1 and SOAP with Attachment specifications

• Used by high-level APIs (such as JAX-RPC runtime)

? Contains API necessary for sending request-response (non-provider-model) messages

? Separated out from JAXM 1.0 into JAXM 1.1 and SAAJ 1.1

175

Web Services Support in EJB 2.1

? Defines Stateless Session Bean-based Web services endpoint model

– Stateless session bean can be web services implementation

– Web services endpoint interface (service definition interface) for Stateless session bean

– Can implement SOAP Message Handlers for Stateless session bean based endpoint

176

JAXR? Standard Java API for performing registry

operations over diverse set of registries

– Web service publication & discovery

? A unified information model for describing business registry content

? Provides multi-layered API abstractions

– Level 0: for UDDI

– Level 1: for ebXML registry/repository

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JAXR Architecture

178

How to Get Started

179

Step1: How to Get Started (for Beginners) for Web-tier? Download and run Java Web Services Developer

Pack (Java WSDP) and its tutorial for web-tier programming (Servlet and JSP)

? Java Web Services Developer Pack Download– java.sun.com/webservices/downloads/webservicespack.html

? Java Web Services Developer Pack Tutorial– java.sun.com/webservices/downloads/webservicestutorial.ht

ml

180

Step2: How to Get Started (for Beginners) for EJB tier and Others

? Download and run J2EE 1.3.1 Reference Implementation (RI)

– In the future course, we will use Sun ONE App Server 7 Platform Edition, which is production quality and is also freely downloadable

? Study J2EE Tutorial from java.sun.com– developer.java.sun.com/developer/onlineTraining/J2EE

/Intro2/j2ee.html

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Step3: Next Step (For Intermediate J2EE Programmers)

? Leverage J2EE Blueprint ? Download and read J2EE Blueprint to learn

the best practice guidelines and design patterns

? Download and run Java Pet Store as an example of J2EE application based on best practice guidelines

– java.sun.com/blueprints/guidelines/designing_enterprise_applications_2e/index.html 182

Step4: Next Step (For Advanced J2EE Programmers) ? Try J2EE IDE of your choice. Sun ONE Studio 4 EE

has 60 day free license with bunch of sample programs you can try

? Sun ONE Studio 4 EE– wwws.sun.com/software/sundev/jde/buy/index.html

? Sun ONE Studio 4 EE tutorial– wwws.sun.com/software/sundev/jde/examples/index.html

? Other vendors also have good quality J2EE IDE's– BEA, IBM, Borland

183

Step5: Next Step (For Advanced J2EE Programmers) ? There is no shortage of quality J2EE online

resources– java.sun.com/j2ee

– www.theserverside.com

184

Step6: Next Step (For J2EE 1.4 Features) ? We will use J2EE 1.4 Beta Reference

Implementation for building J2EE applications that use 1.4 features (or we might use individually released packages)

– JAXP, JAX-RPC, JAXR, SAAJ

– JMX

– Management and Deployment

– JACC

– ...

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185

Next Step (For J2EE 1.4 Features) ? J2EE Application Verification Kit? EcPerf (SPECJAppServer)

186

Evolution of Web Application Frameworks

187

Evolution of MVC Architecture

1.No MVC

2.MVC Model 1

3.MVC Model 2

4.Web application framework (based on MVC Model 2)

? Struts, Sun ONE Application framework

5.Web application framework? JavaServer Faces (JSR-127)

188

Evolution of Web Application Design before MVC Model 2

Model 1 architectureNo MVC

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189

MVC Model 1 Architecture

Browser

JSP(Controller+View)

JavaBeans(Model)

Client Tier Middle TierEnterprise servers/Data sources

190

Why MVC Model 2 Architecture?

? What if you want to present different JSP pages depending on the data you receive?

– JSP technology alone even with JavaBeans and custom tags (Model 1) cannot handle it well

? Solution– Use Servlet and JSP together (Model 2)

– Servlet handles initial request, partially process the data, set up beans, then forward the results to one of a number of different JSP pages

191

MVC Model 2 Architecture

Browser

JSP(View)

Access to Model

Client Tier Middle Tier Enterprise servers/Data sources

Servlet(Controller)

Selection of view

192

Web Application Frameworks? Based on MVC Model 2 architecture? Web-tier applications share common set of

functionality– Dispatching HTTP requests

– Invoking model methods

– Selecting and assembling views

? Provide classes and interfaces that can be used/extended by developers

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193

Why Web Application Framework?

? De-coupling of presentation tier and business logic into separate components

? Provides a central point of control? Provides rich set of features? Facilitates unit-testing and maintenance? Availability of compatible tools ? Provides stability? Enjoys community-supports? Simplifies internationalization? Simplifies input validation

194

Web Application Frameworks

? Apache Struts? Sun ONE Application Framework? JavaServer Faces (JSR-127)

– Standard-based Web application framework

195

Summary &Resources

196

Summary? J2EE is the platform of choice for

development and deployment of n-tier, web-based, transactional, component-based enterprise applications

? J2EE is standard-based architecture? J2EE is all about community? J2EE evolves according to the needs of

the industry

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197

Resources? J2EE Home page

– java.sun.com/j2ee

? J2EE Reference Implementation– http://java.sun.com/downloads/

? J2EE Tutorial– developer.java.sun.com/developer/onlineTraining/J2

EE/Intro2/j2ee.html

? J2EE Blueprint– java.sun.com/blueprints/guidelines/designing_enter

prise_applications_2e/index.html 198

Resources? Java Web Services Developer Pack Download

– java.sun.com/webservices/downloads/webservicespack.html

? Java Web Services Developer Pack Tutorial– java.sun.com/webservices/downloads/webservicestutorial.html

? Sun ONE Studio 4 EE– wwws.sun.com/software/sundev/jde/buy/index.html

? Sun ONE Studio 4 EE tutorial– wwws.sun.com/software/sundev/jde/examples/index.html

? Sang Shin's free J2EE Programming course– www.javapassion.com/j2ee

199

Evaluation Course #ISUN2SN

12/12/2003

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