Serverside Component Technology based on Java Enterprise JavaBean

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Server-side Component Technology based on Java --
Enterprise JavaBean

• Software Engineering College of Sichuan
  University
• Yin Hao (??)
• yinhaoscu_at_263.sina.com

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Chapter 1 Overview

• Now a typical business application is a
  distributed system,we should break up a
  monolithic application into a distributed system
  with multiple clients connecting to multiple
  servers and database over network.
• Figure 1.1 on page 4
• What should we think about according to the above
  scheme?
• Answers are on page 6

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The motivation for EJB

• In the past, most companies built their own
  middleware.
• These days, rather than build them yourself, you
  could buy these middleware services because of
  the appearance of application server (standard).
• Application servers provide you with common
  middleware services, such as resource pooling
  (database, socket) , network, transaction,
  security, and more.
• We build our application out of components.
• Components are not entire applications, they can
  not run alone.
• A company can purchase a well-defined module that
  solve a problem and combine it with other
  components to solve larger problem.

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The motivation for EJB

• An example on page 5 a pricing component
• Different customers can reuse a generic
  component provided by the same vendor.
• The advantages of reusing components
• on page 10 3 points
• Therefore we need a standard between application
  servers and components. This will allow
  components to be switched in and out of various
  application servers without having to change code
  or potentially even recompile the components.

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Thin-Client Multi-tier Application
Tier 1 Client Tier
Web Browser HTML Page
Network
Tier 2 Web Tier
Web Server (Thin-Client Servlet)
Network
Enterprise Beans Application Server
Tier 3 Business Tier
Network
Tier 4 EIS Tier (Enterprise Information System)
Database Server
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Introducing EJB

• Enterprise JavaBean(EJB) is a server-side
  component architecture.(different from Java
  Beans)
• Scalable?reliable ?secure application (thin
  client)
• Rapid application development for server-side
• EJB Standard is a component architecture for
  deployable server-side components in Java
• Specification?interface

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Top three values of EJB

• It is agreed upon by industry. (Train once, code
  anywhere)
• Portability is easier. EJB specification is
  published and available freely to all.
  (java.sun.com)
• Rapid application development.

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Why Java

• EJB components must be written in Java only.
  (restriction)
• Interface/Implementation separation (JDBC)
• Safe and secure (no pointers/automatic garbage
  collection)
• Cross platform (windows/Unix)

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What EJB can do P14

• Performing business logic (back end)
• Access a database (JDBC)
• Access another system (JCA Java Connector
  Architecture)

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Connecting to EJB

• Thick Clients
• Applets?Java Applications
• Dynamically generated web pages
• Java Servlets and JavaServer Pages
• XML-based Web Service wrapper

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Application domain

• Client-side (GUI components)
• rendering GUI
• performing other presentation-related logic
• lightweight business logic
• end-users or business partner
• Server-side (EJB)
• executing complex algorithms
• performing high-volume business transactions
• run in a highly available(247),fault
  tolerant,multi-user secure environment

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EJB Ecosystem(6 roles/Figure 1.7)

• The Bean Provider (Application Component
  Provider)
• The Application Assembler (Application Assembler)
• create a .ear file
• The EJB Deployer (Deployer)
• deploy transaction and security, etc.
• The System Administrator (System Administrator)
• monitoring the runtime environment (Log
  Analyzer?Resource Analyzer)
• The Container and Server Provider (J2EE Product
  Provider)
• IBMs WebSphere?BEAs WebLogic?Macromedias JRun
• The Tool Vendors (Tool Provider)
• IBMs Visual Age for Java (WSAD)?Borlands
  JBuilder?Oracles JDeveloper (IDE)

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J2EE Application
J2EE Application
Web Component
EJB Component
Application Client Component
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J2EE Application Files

• J2EE Application .ear
• J2EE Application Deployment Descriptor .xml
• EJB Component .jar
• EJB Deployment Descriptor .xml
• EJB Class .class
• Remote Interface .class
• Home Interface .class
• Web Component .war
• Web Component Deployment Descriptor .xml
• JSP Files .jsp
• Servlet Class .class
• HTML Files .html
• J2EE Application Client .jar
• J2EE Application Client Deployment
  Descriptor .xml
• Java Application .class

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J2EE Architecture
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Glossary J2EEJava 2 Platform, Enterprise
Edition SSLSecure Sockets Layer RMIRemote
Method Invocation JMSJava Message
Service JNDIJava Naming and Directory
Interface JTAJava Transaction API
JAFJavaBeans Activation Framework RMI/IIOPRMI
over IIOP JDBCJava Database Connection
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J2EE

• The Java 2 Platform, Enterprise Edition
  (J2EE)Providing a platform-independent,
  portable, multi-user, secure and standard
  enterprise-class platform for server-side
  deployment written in the Java language.
• Three different Java platforms
• The Java 2 Platform, Micro Edition (J2ME)
• A development platform for Java-enabled device
  (small devices)
• The Java 2 Platform, Standard Edition (J2SE)
• JDK
• The Java 2 Platform, Enterprise Edition (J2EE)
• A complete development platform for
  enterprise-class server-side deployment in Java.
  J2EE builds on J2SE.

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Java Platform
Microsoft SQL Server JDBC Grid project Globus
Toolkit 3.0
Platforms
J2SDK
J2EE
J2ME
Core/Desktop Application,Applet, Swing, Awt
Enterprise/Server JSP/Servlet, EJB
Mobile/Wireless Midlet (Cell Phone/PDA)
Nokia, Motorola, Siemens SDK JBuilder,Sun One
Studio
IBM WebSphere, WSAD BEA WebLogic, Workshop Sun
One Studio Oracle JDeveloper
Borland JBuilder, JCreator, or Text Editor
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The J2EE Technologies (API)

• Enterprise JavaBeans (EJB)
• Java Remote Method Invocation (RMI) and RMI-IIOP
• RMI-IIOP is an extension of RMI that can be used
  for CORBA integration. RMI-IIOP is the official
  API used in J2EE (not RMI).
• Java Naming and Directory Interface (JNDI)
• EJB components, Data Source and other resources
  across network
• Java Database Connectivity (JDBC)
• accessing relational database

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The J2EE Technologies (API)

• Java Transaction API (JTA) and Java Transaction
  Services (JTS)
• Commit/Rollback, container management
• Java Messaging Service (JMS)
• Message-Driven Bean, asynchronous invocation
• Java Servlets
• Taking requests from some client host (such as a
  web browser) and issue a response back to that
  host.
• Java Pages (JSPs)
• The largest difference between JSP scripts and
  Servlets is that JSP scripts are not pure Java
  code.

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The J2EE Technologies (API)

• Java IDL
• Java-based implementation of CORBA.
• JavaMail
• Allowing you to send email message in a
  platform-independent, protocol-independent manner
  from your Java programs.
• J2EE Connector Architecture (JCA)
• Handling transaction and security concerns.
• The Java API for XML Parsing (JAXP)
• SAX/DOM
• The Java Authentication and Authorization
  Services (JAAS)
• WebShpere vs. .Net