1. Introduction to J2EE
Dr. N. A. Joshi

2. Agenda Section A: Introduction to Java
Evolution
Components
Section B: Enterprise architecture
Types
2-tier, 3-tier, n-tier
Goals of enterprise applications
Introduction to J2EE Platform
Features
J2EE5 APIs
Architecture
Java EE Containers; & Container architecture

3. Section A: Introduction to Java

4. Introduction to Java Platform-independent programming language
Used to create
robust and secure applications, which can run on
single computer or can be distributed among servers and clients
4 aspects of Java
Java Programming Language (JDK)
Java Runtime Environment (JRE)
Java Virtual Machine (JVM)
Java Platform

5. Java Programming Language
An object oriented language
Syntax is similar to C, C++
Fulfills following primary goals of object oriented language:
Uses the object-oriented methodology
Allows the same program to be executed on multiple operating systems
Contains built in support for using computer networks
Executes code securely from remote sources
It is widely used standard in enterprise programming

6. Java Runtime Environment (JRE)
Also known as Java Runtime
Part of Java Development Kit (JDK)
JDK is a set of programming tools required for developing Java apps
JRE consists of-
Java libraries
Java Virtual Machine
Other components essential for running java applications

7. JVM It is an application that actually executes the java program
When JVM is installed on a computer,
It can run Java programs.
Java programs therefore needn’t be self-sufficient, and
they don’t have to include all the machine-level code that actually runs on the computer.
Instead, Java programs are compiled into compact bytecodes, and
the JVM reads and interprets these bytecodes to run your program.
E.g. when you are downloading and applet from internet, you are actually downloading a bytecode
JVM ensures that Java programs include less code, because
all the machine-level code to run your program is already on the target computer and doesn’t need to be downloaded.

8. JVM
JIT Compiler
Initially java programs were interpreted- i.e. executed bytecode by bytecode
Interpretation can be a slow process
To solve this, Java2 comes with JIT compiler-
It actually reads your bytecodes in sections and compiles them interactively into machine language, so that the program can run faster
(the whole program is not compiled at once because java performs runtime checks on various sections of the code)

9. The Java Platform
Over the years, the Java platform evolved into three major editions, each addressing a distinct set of programming needs:
The Java Platform, Standard Edition (Java SE)
Most commonly used among the three editions
Used for developing desktop and console-based applications
It consists of:
A runtime environment
Set of APIs, to build a wide variety of applications comprising standalone applications that can run on various platforms- Windows, Linux, Solaris
The Java Platform, Enterprise Edition (Java EE)
Used for building server-side applications, by using its component-based approach
The Java Platform, Micro Edition (Java ME)
Used for computing micro devices- handheld devices- PDAs, mobile phones – with limited display and memory support

10. Section B: Enterprise Architecture

11. Enterprise Architecture
Helps in understanding the structure of an enterprise application
It can be broken down into three fundamental logical layers:
User interface layer
Displays data elements to the users and collecting data from the users
Often called the ‘presentation’ layer- it includes the part of the software that creates and controls the user interface and validates the user’s actions
Processing layer
Helps an application to work and handle processing of business logic
Also called the ‘business layer’
Data storage & access
Helps the processing layer to read and store data

12. Enterprise Architecture Types
An enterprise application can be designed in many ways,
but, here we discuss the following types of enterprise architectures:
Single-tier architecture
2-tier architecture
3-tier architecture
n-tier architecture

13. Single-tier Architecture
It consists of
the presentation, the business rules, and the data access layers
in a single computing layer.
Such applications are
relatively easy to manage,
and implement data consistency, since data is stored in a single location
Problem-
Such applications can’t be scaled up to handle
multiple users, and
they do not provide an easy means of sharing data across enterprise

14. 2-tier Architecture It separates the data and business logic.
the application resides entirely on the local machine, and
the database is deployed at a specific and secured location.
In 2-tier application (a. k. a. client-server application),
the processing load is entrusted with the client,
while the server simply controls the traffic between the application and data
Data Layer
Data Access Layer
1st Layer
Presentation Logic
Business Logic
Database

15. 2-tier Architecture

16. 3-tier Architecture
In 3-tier architecture, an application is virtually split into three separate logical layers

17. 3-tier Architecture Layers:
First tier: ‘presentation layer’- consists of a GUI to interact with the user
Middle tier: ‘business layer’- consists of the application (or business) logic;
Third tier: ‘data layer’ – contains data access logic needed for the application.
This separation of application logic from the user interface adds enormous flexibility, as compared to the 2-tier system, to the design of an application.
By using this architecture, multiple user interfaces can be built and deployed without changing the application logic; provided it defines a clear interface to the presentation layer.

19. 2-tier vs. 3-tier

20. n-tier Architecture
There can be numerous layers in this kind of architectures.
In this model,
The user interface logic is retrieved from the application running on the desktop.
The application on the desktop is responsible for presenting the user interface to the end user and for communicating to the business logic tier.
It is no longer responsible for enforcing business rules or accessing databases.
There is no hard & fast way to define an application in this architecture.
In fact, n-tier architecture can support a number of different configurations.

21. n-tier Architecture
It can be virtually distributed in to the following segments:

22. n-tier Architecture Advantages Improved maintainability Consistency
Such applications are easier to maintain
Consistency
By means of component designing and their association with the layer in the architecture where they are providing functionality
Interoperability
Such applications are highly interoperable, as we can implement components in different layers to support different technologies and platforms
Flexibility
Developer is free to design and develop various types of components for different layers with all flexibility
Scalability
We can add new components without affecting the performance of the existing application

23. Goals of enterprise applications
Ensure robustness
Ensure scalability and performance
Implement OO design principles
Avoid complexity
Ensure maintainability and extensibility
Ensure ease of testing
Promote reuse of applications
Support for multiple client types
portability

24. Section C: Java EE Platform

25. Applications Development Requirement
Platform independence - Do not get caught in complexity of operating systems
Develop Once, run every
Strong framework, ensure repeatability – Ensure building blocks
Flexibility in individual implementation over common rules
Internationalization requirements
Access of business rules including data and methods
Reduced dependency on database
Organization component modelling
Standardization with Business entities
Technology Portability
Ability to change business rules easily
J2SE (Java 2 Standard Edition) : JVM, tools, Libraries and Doc
J2EE Java 2 Enterprise Edition
J2EE adds additional specifications, libraries, documentation and tools
Standard based: The J2EE Connector Architecture defines a standard, transactionally capable, scalable, and secure architecture for leveraging EIS investment -- thereby simplifying integration with such mainframe applications as Enterprise Resource Planning (ERP) and Customer Relationship Management (CRM) systems.
Some of the J2EE Application Servers available are
Apache (Servelet/ JSP container Only)
IBM WebSphere
JRun
JBoss
BEA WebLogic
TCS Internal

26. What is J2EE? J2EE is a standard based platform for
developing, deploying and managing multitier, web-enabled, server centric and component based enterprise applications
J2EE enhances J2SE with:
Enterprise JavaBeans components
Java Servlets API
Java Server Pages
XML
This suite is the Java 2 Enterprise Edition, commonly known as J2EE.
J2EE (Java2 Enterprise Edition) offers a suite of software specification to design, develop, assemble and deploy enterprise applications.
It provides a distributed, component-based, loosely coupled, reliable and secure, platform independent and responsive application environment.
J2EE environment provides a framework for bundling together the components into an application and provide the applications necessary common services such as persistence, security, mail, naming and directory service etc.
Java 2 Platform, Enterprise Edition (J2EE) defines the standard for developing component-based multi-tier distributed enterprise applications.
A J2EE component is a self-contained functional software unit that is assembled into a J2EE application along with related components.
Application logic is divided into components according to function
J2SE (Java 2 Standard Edition) : JVM, tools, Libraries and Doc
J2EE Java 2 Enterprise Edition
J2EE adds additional specifications, libraries, documentation and tools
Standard based: The J2EE Connector Architecture defines a standard, transactionally capable, scalable, and secure architecture for leveraging EIS investment -- thereby simplifying integration with such mainframe applications as Enterprise Resource Planning (ERP) and Customer Relationship Management (CRM) systems.
Some of the J2EE Application Servers available are
Apache (Servelet/ JSP container Only)
IBM WebSphere
JRun
JBoss
BEA WebLogic
TCS Internal

27. Exploring the Java EE5 platfom
It comprises of the following:
A runtime infrastructure for managing and hosting applications. All runtime applications are hosted in this server.
A set of Java APIs to build applications. These Java APIs describe the programming model for Java EE appliations.

28. The Runtime Infrastructure
It includes numerous services to manage enterprise applications.
The Java EE architecture provides the uniform means of accessing platform-level services via its runtime environment.
These services include:
messaging, security and distributed transactions

29. The Java EE APIs
In the enterprise services, the distributed applications require server access for running.
These enterprise services include transaction processing, managing, multithreading, and database access.
J2EE5 unifies access to such services in its enterprise service APIs.
The j2ee5 application program can access these APIs through the containers such as Web and EJB,

30. Java EE APIs

31. EJB 3.0
An enterprise bean is a server-side piece of code with fields and methods to implement the modules of the business logic.
It is a building block that can be used alone or with other enterprise beans to execute the business logic on the Java EE server
It is a component based architecture for developing, deploying, and managing reliable enterprise applications

32. Java Servlet Technology
It allows you to define HTTP-specific servlet-classes.
A servlet class extends the capabilities of servers that host the applications accessed by the way of request-response programming model.

33. Java Server Pages & JSP Tag Library(JSTL)
It allows you to integrate the combined snippets of Java code with static markup in a text-based document.
It is a text-based document that contains two types of text:
Static template data, which can be expressed in any text-based format such as HTML or XML
JSP elements, which determine how the page constructs the dynamic content
JSTL provides a set of standard tags that can be used in a JSP page
It provides tags to use java code embedded in a JSP page
It includes various tags to control the flow of execution, to support internationalization and to access database using SQL

34. Java Server Faces
Provides component based API for building rich user interfaces for web applications.
Used in conjunction with JSP and servlets
They handle all the complexities of managing the UI, enabling the developer to concentrate on the business logic.

35. Java Message Service (JMS)
The JMS API is a messaging standard that allows Java EE application components to create, send, receive, and read messages.
It enables distributed communication that is loosely coupled, reliable, and asynchronous.

36. Java Transaction API(JTA)
JTA is used to manage distributed transactions.
This API specifies a standard java interface for a transaction manager to interact with the resource manager, application server, and transactional appliacations.

37. JavaMail API
Many enterprise applications need to send notifications.
Java EE platform includes the JavaMail API with a JavaMail Service provider that application components can use to send s.
It has two parts:
An application-level interface used by the application components to send s
A service provider interface

38. JavaBeans Activation Framework (JAF)
it provides the standard services –
to determine the type of an arbitrary
to encapsulate access to it
to identify the operations available on it, and
to instantiate appropriate JavaBean components to perform these operations

39. Java API for XML Processing (JAXP)
it enables applications to parse, transform, validate, and query XML documents
This API is independent of XML processor implementation

40. Java API for XML Web Services(JAX-WS)
The JAX-WS specification helps
create web service endpoints and client components to access the web services.
It also describes the deployment information of web services and clients.
It also supports JAXB
JAXB API is used to bind XML data to java objects.

41. Java Architecture for XML Binding(JAXB)
It helps on binding an XML schema with a java object in a simple and easy way.
It helps in marshalling java content tree into XML instance documents, and vice versa.

42. JDBC API
The Java DataBase Connectivity API helps execute SQL commands from Java programs.
JDBC API can be used with
Enterprise java beans,
JSP,
Servlets, and
Java classes

43. Java Persistence API (JPA)
In Java EE, a solution for persistence has been provided in the form of JPA.
An object relational mapping, which is used by persistence, is used for bringing an OO model and relational database model together.
JPA consist of
the Persistence API,
query language, and
object/relational mapping metadata.

44. Java Naming and Directory Interface (JNDI)
It provides the naming and directory functionality.
It provides Java EE applications with the methods to perform standard directory operations, such as
associating attributes with the objects and searching for the objects by using their attributes.
Using JNDI, a Java EE application can store and retrieve any type of named Java objects.

45. Java Authentication and Authorization Service (JAAS)
JAAS provides a way for a Java EE application to authenticate and authorize a specific user or group of users.
JAAS is a Java based standard Pluggable Authentication Module (PAM) framework,
which extends the Java platform security architecture to support user-based authorization.

46. J2EE Suite (summary)
Core technology: Container infrastructure, language and environment support
XML technology
The Java API for XML Processing (JAXP)
The Java API for XML-based RPC (JAX-RPC)
SOAP with Attachments API for Java (SAAJ)
The Java API for XML Registries (JAXR)
Web Technology
Java Servlets
JavaServer Pages
JavaServer Pages Standard Tag Library
Enterprise Java Bean (EJB) technology
Session beans
Entity beans
Enterprise JavaBeans Query Language
Message-driven beans
Platform services
Security
Transactions
Resources
Connectors
Java Message Service

47. Architecture of Java EE 5

48. Distributed Multi-tiered Applications
Services, clients (people and application) and data are distributed geographically across many platforms and many machines.
Multiple tiers:
Client-tier (browser or client-application)
Web-tier (web-server: Java Server Pages)
Business-tier (logic; Examples: Enterprise Java Beans)
Enterprise-Information-System (EIS) tier (database)

49. Enterprise Application Model

50. J2EE Multi-tier Framework
EJB Container
JSP/Servlet
Container
WEB CLIENT
Database/Legacy Systems
ANY CLIENT
Client
Tier
EIS Tier
Web
Business
Machine
J2EE
Server
Database
Server /
Legacy
Business logic is in EJB (Enterprise Java Bean) container and can be accessed either by a web client (browser) or any other client. These clients include swing based GUI applications, other applications developed in other platform and programming languages, applications running on PDAs (Personal Digital Assistant) and mobile phones etc.
EIS – Enterprise Information Systems (legacy systems).
Container is a logical concept which holds components.
Client is a software sitting on the desktop interacting with server through network using some protocol.

51. J2EE Architecture CLIENTS TIER BACK END
External Clients from INTERNET
(Browsers , WAP etc.) Applets
Internal Clients from INTRANET
(Browsers , Desk top
Applications etc.)
Applets, Javabeans
BACK END
J2EE WEB APPLICATION SERVER TIER
PRESENTATION LOGIC
(Web Components)
BUSINESS LOGIC
(EJB Container )
ENTERPRISE SERVICES
HTML
JDBC
XML
SERVLETS
JSP
WML
EJB
JNDI
JMS
JTS
RMI - IIOP
Enterprise
Information
Systems
(Databases,
ERP,
Legacy Systems)
Applets : An applet is a small client application written in the Java programming language that executes in the Java virtual machine installed in the Web browser. client systems will likely need the Java Plug-in and possibly a security policy file in order for the applet to successfully execute in the Web browser.
Application clients: Swing bases rich GUI. Either can access data tier directly or through HTTP socket connection.
Web clients:
A web client consists of two parts:
Dynamic Web pages containing various types of markup language (HTML, XML, and so on), which are generated by Web components running in the Web tier, and
A Web browser, which renders the pages received from the server.
A Web client is sometimes called a thin client. Thin clients usually do not query databases, execute complex business rules, or connect to legacy applications. When you use a thin client, such heavyweight operations are off-loaded to enterprise beans executing on the J2EE server, where they can leverage the security, speed, services, and reliability of J2EE server-side technologies.
Web tier consists of servlets and JSP pages. It is also called presentation layer/logic/tier.
Enterprise Java Beans capture the business logic. They are kept in EJB containers.
Apart from these, J2EE provides some common services like, messaging, mail, lookup etc.
Various devices can interact with application in XML (Extensible Markup Language), HTML and WML (Wireless Markup Language) format

52. J2EE-based Application
The J2EE APIs enable distributed systems and applications through the following:
Unified application model across tiers with enterprise beans
Simplified response and request mechanism with JSP pages and servlets
Reliable security model with JAAS
XML-based data interchange integration with JAXP
Simplified interoperability with the J2EE Connector Architecture
Easy database connectivity with the JDBC API
Enterprise application integration with message-driven beans and JMS, JTA, and JNDI

53. J2EE Technology Architecture
html
Web clients
Application clients
IIOP,
others
Java Server
pages
Servlets
Enterprise Java Beans Components
Server
platform
JTS
JMAPI
JNDI
JMS
JAXP
JDBC
JAAS …

54. J2EE offerings for Developer
Java Server Pages
JavaMail API
Enterprise Java
Beans
Java Authentication &
Authorization Service
Java Naming &
Directory Interface
JAXP – JAXB –
JAXR – JAXRPC
Java Servlet
Technology
JDBC
Java Message Service
J2EE
Java Transaction API
& Service
JTA + JTS
SAAJ (Web Services)
Enterprise Java Beans is used to capture business logic.
Servlets and JSP provides a mechanism to communicate between clients (browsers) and servers.
JDBC is the middle tier used to talk to underlying database.
Naming service is used to lookup various components dynamically during runtime.
Authentication and authorization service is used to provide role based access to various users.
Messaging service is used form inter-component communication.
Transaction is used to ensure that atomicity is maintained for each transaction.

55. J2EE Application Components
J2EE applications comprises various components.
Client Components
Built using applets which runs on client machine
Web Compoents
Built using Java Servlet technology and JSP technology which runs on server.
Business Compnents
Built using EJB technolgy which runs on server.
Web clients
Dynamic web pages with HTML, rendered by web browsers.
Can include applets.
Communicates with server typically using HTTP.
Application clients
User interface using GUI components such as Swing and AWT.
Directly accesses the business logic tier.
Components are self contained software modules which can be used for plug-and-play kind of software development. If want to change one functionality, the current component can be replaced by another component without affecting the whole application.

56. Web Components J2EE Web components can be either servlets or JSP pages
Servlets are Java programming language classes that dynamically process requests and construct responses.
JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content
Static HTML pages and applets are bundled with Web components during application assembly, but are not considered Web components by the J2EE specification.
Server-side utility classes can also be bundled with Web components and, like HTML pages, are not considered Web components.

57. Web Tier
As shown in the next slide Figure the Web tier, like the client tier, might include a JavaBeans component to manage the user input and send that input to enterprise beans running in the business tier for processing

58. Business Tier
Business code, which is logic that solves or meets the needs of a particular business domain such as banking, retail, or finance, is handled by enterprise beans running in the business tier.

59. Java 2 Enterprise Edition (J2EE) Example
Java 2 Enterprise Edition (J2EE) (continued)
An EJB Container is a run-time environment that controls the enterprise beans and provide system-level services such as:
Transaction management, security (through deployment descriptors)
Remote client connectivity (through Java RMI over IIOP protocol)
Life cycle management such as creating and removing the beans, and maintaining the beans in their active and passive states
Database connection pooling to maintain a pool of database connections, thus reducing the cost and time involved in obtaining database connections.
A database is a persistent storage for the data.
Instructor Note
The details of servlets and JSPs are covered in other courses. Do not discuss them here in detail. Various terms introduced here such as deployment descriptors and life cycle management are discussed in detail in the following lessons.
J2EE server
Web Container
HTTP Request
Servlet
HTTP Response
Client
(Browser)
Bean1
Bean2
EJB Container
Database

60. Containers Containers are a central theme in J2EE architecture.
Containers are like the rooms in the house-
People and things exist in the rooms, and interface with the infrastructure through well-defined interfaces.
In an application server,
Web and business components exist inside the containers and interface with the Java EE infrastructure through well-defined interfaces.

61. J2EE Containers What is a Container
Containers are the interface between a component and the low-level platform specific functionality that supports the component.
How does it work
Container settings are specified for each component during assembly process before deployment.
What do I get
Support for security, transaction management, JNDI lookup, Remote connectivity.
Here are some of the highlights:
The J2EE security model lets you configure a Web component or enterprise bean so that system resources are accessed only by authorized users.
The J2EE transaction model lets you specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit.
JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access naming and directory services.
The J2EE remote connectivity model manages low-level communications between clients and enterprise beans. After an enterprise bean is created, a client invokes methods on it as if it were in the same virtual machine.

62. J2EE Containers (cont..) Manage life cycle of objects
Manage transactions
Provide security
Resource optimization
DB pooling
Compiled JSP Caching
Persistence support
CMP (EJB-QL)
Here are some of the highlights:
The J2EE security model lets you configure a Web component or enterprise bean so that system resources are accessed only by authorized users.
The J2EE transaction model lets you specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit.
JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access naming and directory services.
The J2EE remote connectivity model manages low-level communications between clients and enterprise beans. After an enterprise bean is created, a client invokes methods on it as if it were in the same virtual machine.
CMP – Container Managed Persistence
EJB–QL – Enterprise Java Bean Query Language (similar to SQL).

63. Types of Containers EJB Container Web Container
Application Client Container
Applet Container

65. Compilation and Deployment
Compilation (building the executables) uses build tool such as Apache Ant.
The components of the various tiers are packaged: .jar, .war, .ear
Declarative resources are added.
A deploy tool or management tool is used to deploy the packaged units into a J2EE server (container).

66. Thank You