Java EE Overview

Agenda

• What is Java EE?
• Evolution of Enterprise Application Development Frameworks 
• Why Java EE? 
• Java EE Platform Architecture
• How to get started

What is Java EE?

• Open and standard based platform for
• developing, deploying and managing
• n-tier, Web-enabled, server-centric, and component-based enterprise applications

The Java™ Platform

Evolution of Enterprise Application Development Frameworks

• Single tier 
• Two tier
• Three tier
  • RPC based
  • Remote object based 
• Three tier (HTML browser and Web server) 
• Proprietary application server 
• Standard application server

About Enterprise Applications

• Things that make up an enterprise application
  • Presentation logic
  • Business logic
  • Data access logic (and data model)
  • System services
• The evolution of enterprise application framework reflects
  • How flexibly you want to make changes
  • Where the system services are coming from

Single Tier (Mainframe-based)

• Dumb terminals are directly connected to mainframe 
• Centralized model (as opposed distributed model) 
• Presentation, business logic, and data access are intertwined in one monolithic mainframe application

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

Two-Tier

• Fat clients talking to back end database
  • SQL queries sent, raw data returned 
• Presentation,Business logic and Data Model processing logic in client application

•  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

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.

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 tightlycoupled (than the three-tier object based model)
  • Code is not really reusable (compared to object model based)

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

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

Three-Tier (Web Server)

• Browser handles presentation logic 
• Browser talks Web server via HTTP protocol 
• Business logic and data model are handled by “dynamic contents generation” technologies (CGI, Servlet/JSP, ASP)

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

Trends

• Moving from single-tier or two-tier to multitier architecture 
• Moving from monolithic model to objectbased application model 
• Moving from application-based client to HTML-based client

Single-tier vs. Multi-tier

Monolithic vs. Object-based

Outstanding Issues & Solution

• Complexity 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 based

Proprietary Solution

• Use "component and container" model
  • Components captures business logic
  • Container provides system services 
• The contract between components and container is defined in a well-defined but with proprietary manner 
• Problem of proprietary solution: Vendor lock-in 
• Example: Tuxedo, .NET

Open and Standard Solution

• Use "component and container" model in which container provides system services in a well-defined and as industry standard 
• Java EE is that standard that also provides portability of code because it is based on Java technology and standardbased Java programming APIs

Why Java EE?

Platform Value to Developers

• Can use any Java EE implementation for development and deployment
  • Use production-quality standard implementation which is free for development/deployment
  • Use high-end commercial Java EE products for scalability and fault-tolerance 
• Vast amount of Java EE community resources
  • Many Java EE related books, articles, tutorials, quality code you can use, best practice guidelines, design patterns etc. 
• Can use off-the-shelf 3rd-party business components

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

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

Java EE APIs & Technologies

• Java EE 1.4 APIs and Technologies
• J2SE 1.4 (improved) 
• JAX-RPC (new) 
• Web Service for Java EE 
• Java EE Management 
• Java EE 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

Java EE 5

• JAX-WS 2.0 & JSR 181 
• Java Persistence 
• EJB 3.0 
• JAXB 2.0 
• JavaSever Faces 1.2 new to Platform 
• JSP 2.1 Unification w/ JSF 1.2 
• StAX Pull Parser new to Platform

J2EE is an End-to-End Architecture

The Java EE Platform Architecture

Java EE is End-to-End Solution

N-tier Java EE Architecture

Java EE Component & Container Architecture

Java EE Containers & Components

Containers and Components

• Containers do their work invisibly
  • No complicated APIs
  • They control by interposition 
• Containers implement Java EE
  • Look the same to components
  • Vendors making the containers have great freedom to innovate

Java EE Application Development & Deployment Life Cycle

• Write and compile component code
  • Servlet, JSP, EJB 
• Write deployment descriptors for components
  • From Java EE 5, you can use annotations 
• Assemble components into ready-todeployable package
• Deploy the package on a server

 Life-cycle Illustration

Java EE Development Roles

• Component provider
  • Bean provider 
• Application assembler 
• Deployer 
• Platform provider
  • Container provider 
• Tools provider 
• System administrator

The Deployment Descriptor

• Gives the container instructions on how to manage and control behaviors of the Java EE components
  • Transaction
  • Security
  • Persistence 
• Allows declarative customization (as opposed to programming customization)
  • XML file 
• Enables portability of code

Java EE Application Anatomies

Possible Java EE Application Anatomies

Java EE Application Anatomies

• 4-tier Java EE applications
  • HTML client, JSP/Servlets, EJB, JDBC/Connector 
• 3-tier Java EE applications
  • HTML client, JSP/Servlets, JDBC 
• 3-tier Java EE applications
  • EJB standalone applications, EJB, JDBC/Connector 
• B2B Enterprise applications
  • Java EE platform to Java EE platform through the exchange of JMS or XML-based messages

Which One to Use?

• Depends on several factors
  • Requirements of applications
  • Availability of EJB tier
  • Availability of developer resource

How to Get Started

Step1: For Beginners and Intermediate Java EE Programmers

• Follow along with this course
• Start using Java EE IDE of your choice 
• Try open source IDE's
  • NetBeans IDE (netbeans.org)
  • Eclipse

Step2: Next Step (For Advanced Java EE Programmers)

• Learn practical open-source solutions
  • Spring framework (for light-weight framework)
  • Hibernate (for O/R mapping)
  • JDO (for transparent persistence)
  • Struts, WebWork, Tapestry (for Web-tier frameworks)
  • JUnit (for unit testing)
  • Log4j (for logging)
  • Many more

Summary & Resources

Summary

• Java EE is the platform of choice for development and deployment of n-tier, web-based, transactional, componentbased enterprise applications 
• Java EE is standard-based architecture 
• Java EE is all about community 
• Java EE evolves according to the needs of the industry

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