Introduction to Java EE (J2EE) MVC and Core Concepts

Introduction to Java EE (J2EE)


Atit Patumvan, Lecturer
Faculty of Management and Information Sciences
Naresuan University

Atit Patumvan, Faculty of Management and Information Sciences, Naresuan University.

2

Model View Controller Design Pattern
● MVC is an acronym for Model View Controller
● MVC pattern separates the modeling of the domain, the presentation,
and the actions based on user input into three separate classes
● Very popular, used extensively in Java and other languages.


3

Core Elements of MVC
● Model: Contains the data model and all information that identifes
the state of the application. It is generally self-consistent and
independent of the other elements.
● View: Stands on the other side in respect to the model and defnes
the representation of the data stored in the model. The view is
commonly identifed as your application's user interface (or GUI) or, in
case of Web applications, the browser Webpage.
● Controller: Represents the application logic. Here, it is defned how
the user can interact with the application and how user actions are
mapped to model changes


4

Standard MVC Structure

Controller

notifies user interaction Handles model updates

View Model

Update the views
on model changes


5

Demo


6

What is J2EE?


7

The Java Platform


8

The Java Platform
Optional
Packages
Optional
Packages

J2ME
CDC
J2EE
J2EE Foundation Profile MID Profile

CDC CLDC Java Card API

Java Virtual Machine CVM KVM CardVM


9

What is the J2EE
● Open and standard based platform for
● Developing, deploying and managing
● N-tier, Web enabled, server-centric, and component based enterprise
application


10

What Makes Up J2EE?
● API and Technology J2EE
J2EE J2EE
J2EE
Specification Reference
specifcations Specification Reference
Implementation
Implementation
● Development and Deployment
Platform J2EE

● Standard and production-
quality implementation J2EE
J2EE J2EE
J2EE
Compatibility
Compatibility Application
Application
● Compatibility Test Suite (CTS) Test
Test
Suite
Programming
Programming
Model
Suite Model
● J2EE brand
● J2EE blueprint
● Sample Code

11

Open and Standard Solution
● Use “component and container” model in which container provides
system services in a-well defned as an industrial standard
● J2EE is that standard that also provides portability of code because it
is based on Java technology and standard-based Java programming
APIs


12

Platform Value to Developer
● Can use any J2EE implementation for development and deployment
● Vast amount of J2EE community resources
● Can use off-the-shelf 3rd party business components


13

Platform Value to Vendors
● Vendors work together on specifcations and then complete in
implementation
● Scalability, Performance, Reliability, Availability, Management and
development tools, and so on
● Freedom to innovate while maintaining the portability of application
● Do not have to create and maintain their own proprietary API


14

Platform Value to Business Customers
● 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 application and platforms
● Large developer pool


15

J2EE API and Technologies


16

J2EE 1.4 APIs and Technologies
● J2SE 1.4 (Improved) ● Servlet 2.4
● JAX-RPC (new) ● JSP 2.0
● Web Services for J2EE ● EJB 2.1
● J2EE Management ● JAXR
● J2EE Deployment ● Connector 1.5
● JMX 1.1 ● JACC
● JMS 1.1 ● JAXP 1.2
● JTA 1.0 ● JavaMail 1.3
● JAF 1.0

17

Java EE 5
● JAX-WS 2.0 & JSR 181
● Java Persistence
● EJB 3.0
● JAXB 2.0
● JavaServer Face 1.2 – new to Platform
● JSP 2.1 – Unifcation with JFS 1.2
● StAX – Pull Parser – new to Platform


18

J2EE Components


19

Java Servlet


20

What is Java Servlets
● Servlets are the Java Platform technology of choice for extending and
enhancing web server.
● Servlets provide a component-based, platform-independent method
for building web-based, without the performance limitation of CGI
Programming.
Request CGI1
Child for CGI1
Request CGI2 CGI Child for CGI2
Based Webserver
Request CGI1 Child for CGI1

Request Servlet1 Servlet Based Server
Request Servlet2 Servlet1
JVM
Request Servlet1 Servlet2


21

Java Servlets
● Servlets have access to entire family of Java APIs, including the JDBC
to access enterprise databases.
● Servlet can also access a library of HTTP Specifc call and receive all
the benefts of mature Java language, including portability,
performance, reuseability and crash protection


22

Anatomy of a Servlet
● init() – the init() function is called when the servlet is initialized by the
server. This often happens on the frst doGet() or doPut() call of the
servlet.
● destroy() – this function is called when the servlet is being destroyed
by the server, typically when the server process is being stopped.

Source: http://java.sun.com/docs/books/tutorial/servlets/lifecycle/index.html


23

● doGet() – the doGet() function is called when the servlet is called via
an HTTP GET.
● doPost() – the doPost() function is called when the servlet is called
via an HTTP POST.
● POSTs are a good way to get input from HTML forms



24

● HTTPServletRequest object ● HTTPServletResponse object
● Information about an HTTP ● Used for formatting an HTTP
request response
– Headers – Headers
– Query String – Status codes
– Session – Cookies
– Cookies



25

Demo


26

Sample Servlet: HelloWorld.java
01: package com.patumvan.atit.servlets;
02:
03: import java.io.*;
04: import javax.servlet.*;
05: import javax.servlet.http.*;
06:
07: public class HelloWorld extends HttpServlet {
08:
09: protected void processRequest(HttpServletRequest request,
HttpServletResponse response)
10: throws ServletException, IOException {
11: response.setContentType("text/html;charset=UTF-8");
12: PrintWriter out = response.getWriter();
13: try {
14: out.println("<html>");
15: out.println("<head>");
16: out.println("<title>Servlet HelloWorld</title>");
17: out.println("</head>");
18: out.println("<body>");
19: out.println("<h1>Servlet HelloWorld </h1>");
20: out.println("</body>");
21: out.println("</html>");
22: } finally {
23: out.close();
24: }
25: }
:

27

Sample Servlet: HelloWorld.java
:
30: @Override
31: protected void doGet(HttpServletRequest request, HttpServletResponse response)
33: processRequest(request, response);
34: }
35:
36: @Override
37: protected void doPost(HttpServletRequest request, HttpServletResponse response)
39: processRequest(request, response);
40: }
41:
42: @Override
43: public String getServletInfo() {
44: return "Short description";
45: }
46: }


28

Sample Servlet: /WEB-INF/web.xml
01: <?xml version="1.0" encoding="UTF-8"?>
02: <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
03: <servlet>
04: <servlet-name>HelloWorld</servlet-name>
05: <servlet-class>com.patumvan.atit.servlets.HelloWorld</servlet-class>
06: </servlet>
07: <servlet-mapping>
08: <servlet-name>HelloWorld</servlet-name>
09: <url-pattern>/HelloWorld</url-pattern>
10: </servlet-mapping>
11: <session-config>
12: <session-timeout>
13: 30
14: </session-timeout>
15: </session-config>
16: <welcome-file-list>
17: <welcome-file>index.jsp</welcome-file>
18: </welcome-file-list>
19: </web-app>


29

What is Java Server Pages (JSP)?


30

JSP – Java Server Pages
● JavaServer Pages technology uses XML-like tags and scriptlets written
in the Java programming language to encapsulate the logic that
generates the content for the page.
● Any and all formatting (HTML or XML) tags are passed directly back to
the response page.
● By separating the page logic from its design and display and
supporting a reusable component-based design, JSP technology
makes it faster and easier than ever to build web-based applications


31

Sample JSP: /index.jsp
01: <%@page contentType="text/html" pageEncoding="UTF-8"%>
02: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
03: "http://www.w3.org/TR/html4/loose.dtd">
04:
05: <html>
06: <head>
07: <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
08: <title>JSP Page</title>
09: </head>
10: <body>
11: <h1>Hello World!</h1>
12: </body>
13: </html>


32

EJB
(Enterprise Java Beans)


33

What is EJB technology?
● A server-side component technology
● Easy development and deployment of Java technology-based
application that are:
● Transactional, distributed, multi-tier, portable, scalable, secure, …


34

Why EJB Technology?
● Leverages the benefts of component-model on the server side
● Separates business logic from system code
● Container provides system services
● Provides framework for portable components
● Over different J2EE-compliant servers
● Over different operational environments
● Enables deployment-time confguration
● Deployment descriptor


35

EJB – Enterprise Java Beans
● Enterprise Java Beans are components that are deployed into
containers
● The container provides services
● Loading / Initialization
● Transactions
● Persistence
● Communication with EJB clients
● Enterprise Naming Context (JNDI name space)


36

EJB Architecture


37

Enterprise Java Beans
Enterprise JavaBeans

Synchronous communication Asynchronous communication
Session Bean Entity Bean Message-Driven Bean

Stateless Stateful

Bean managed Container managed
Persistence Persistence
(BMP) (CMP)


38

JMS
(Java Message Services)


39

Java Messing Service (JMS)
● Messaging systems (MOM) provide
● De-coupled communication
● Asynchronous communication
● Plays a role of centralized post offce
● Benefts of Messaging systems
● Flexible, Reliable, Scalable communication systems
● Point-to-Point, Publish and Subscribe
● JMS defnes standard Java APIs to messaging systems


40

Connector Architecture


41

m x n Problem
m n

App SAP
Server1

App
EIS2
Server2

App EIS3
Server3

App EIS4
Server


42

Connector Architecture
● Defnes standard API 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's) Adaptors
● With Connector architecture, same adaptor works with all J2EE
compliant containers
● 1 (common to all App servers) x n (# of EIS's) Adaptors


43

JAAS
(Java Authentication & Authorization Services)


44

JAAS: Authentication
● Pluggable authentication framework
● Userid/password
● Smartcard
● Kerberos
● Biometric
● Application portability regardless of authentication schemes
underneath
● JAAS provides authentication scheme independent API
● Authentication schemes are specifed Login confguration fle, which will be
read by JAAS

45

JAAS Pluggable Authentication


46

Other J2EE APIs and Technologies


47

Java Naming and Directory Interface (JNDI)
● Utilized by J2EE applications to locate resources and objects in
portable fashion
● Applications use symbolic names to fnd object references to resources via
JNDI
● The symbolic names and object references have to be confgured by
system administrator when the application is deployed.


48

Java Database Connector (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.


49

J2EE is End to End Architecture


50

The J2EE Platform Architecture
B2B
Applications
Existing
Applications

B2C
Applications

Web
Services
Enterprise
Information
Wireless Application Server Systems
Applications


51

N-tear J2EE Architecture

Web Tier EJB Tier


52

J2EE Deployment
● JAR – Java ARchive
● Java class fle
● EJBs
● WAR - Web ARchive
● Servlets
● JSPs
● EAR - Enterprise ARchive
● Contains other JARs and WARs to form an entire application
● Deployment descriptors
● XML

53

J2EE Server
● Application Server
● As of Sept ’01 - MetaGroup Survey by sales $$
– BEA Weblogic - 37%
– IBM Websphere – 22%
– Oracle – 11%
– Iplanet – 5%
– Other- 12%
● Open-source
– Jboss – www.jboss.org
● Sun’s listing of J2EE compatible servers
– http://java.sun.com/j2ee/compatibility.html

54

J2EE Servers
● Servlet / JSP Servers
● Most of the commercial application servers also include servlet / JSP
support
● Open-Source
– Apache Tomcat
– Jetty
● Sun’s listing of servlet / JSP servers
● http://java.sun.com/products/servlet/industry.html


55

J2EE Development Tools
● Major IDEs support J2EE in some form
● Wizards for EJB / Servlets
● Custom editors for JSP
● Deployment descriptor support
● Deployment support for application servers
● Embedded servers for testing within IDE


56

Learning More...
● Enterprise JavaBeans – 3rd Edition
● Richard Monson-Haefel, O’Reilly © 2001
● JBoss documentation
● http://www.jboss.org/online-manual/HTML/index.html
● Designing Enterprise Applications with the Java 2 Platform, Enterprise
Edition
● Nicholas Kassem and the Enterprise Team, Addison Wesley © 2000
● Core Servlets and JavaServer Pages (JSP)
● Marty Hall, Prentice Hall © 2000


57

Learning More ...
● J2EE Tutorial - http://java.sun.com/j2ee/tutorial/1_3-fcs
● J2EE Developers Guide -
http://java.sun.com/j2ee/sdk_1.2.1/techdocs/guides/ejb/html/DevGui
deTOC.html
● JNDI - http://java.sun.com/products/jndi/tutorial/
● JMS - http://java.sun.com/products/jms/tutorial/
● JDBC - http://java.sun.com/docs/books/tutorial/jdbc
● Servlets - http://java.sun.com/docs/books/tutorial/servlets
● JSP - http://java.sun.com/products/jsp/docs.html
● JAXP - http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial

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