1. 第十四章 J2EE 入门 Introduction What is J2EE ?
The Platform for Enterprise Solutions
J2EE Application Programming Model
J2EE Benefits
 J2EE Platform Technologies
J2EE Application Scenarios
J2EE Application Construction

2. ‘Enterprise’ in J2EE
‘Programming in the large’ and ‘enterprise computing’ :
Lots of users and the application has an ‘extended life’
Deployed on heterogeneous computing environments
Maintainability, Flexibility, Reusability are major issues
Needs to support transactions, resource-pooling, security, threading, persistence, life-cycle management etc…
Need for special solutions to manage complexity
Proprietary frameworks and middleware
Need for standard APIs for enterprise computing
Multi-tiered architecture in enterprise applications

3. What is J2EE?
J2EE means :
J2EE Platform - A standard platform for hosting J2EE applications, specified as a set of required APIs, specifications and policies.
J2EE Application Programming Model - A standard programming model for developing multi-tier, thin-client applications.
J2EE Compatibility Test Suite - A suite of compatibility tests for verifying that a J2EE platform product is compatible with the J2EE platform standard.
J2EE Reference Implementation - A reference implementation for demonstrating the capabilities of J2EE and for providing an operational definition of the J2EE platform.

4. J2EE Platform

5. J2EE Platform

6. Multitiered Distributed
Application Model
• J2EE platform is a multitiered distributed application model
• Application logic divided into components according to function
• Various components installed on different machines depending on which tier in the multitiered J2EE environment the application component belongs

7. Multitier Applications

8. Client tier

9. Web tier

10. Business and EIS Tiers

11. J2EE Platform Benefits  Simplified architecture and development
 Integration with existing information systems
 Scalability to meet demand variations
 Choices of servers, tools, components
 Flexible security model

12. J2EE Platform Technologies
Component Technologies
J2EE Containers
 Platform Service
Communication Technologies
Platform Roles

13. J2EE Application Components

14. J2EE Application Components
Self-contained functional software unit assembled into a J2EE application
• Client components - application clients or applets
• Web components - Servlets or JSP
• run on the server
• may respond to HTTP requests from client
• typically contains presentation logic
• dynamically generates HTML pages, XML or other data format
• Business components - EJB

15. J2EE Containers

16. Container Services
Containers are the interface between a component and the low-level platform-specific functionality.
Before a component can be executed, it must be assembled into a J2EE application and deployed into its container.
The assembly process involves specifying container settings for each component and for the J2EE application itself.
Container services:
security
transaction management
Java Naming and Directory Interface (JNDI) lookups
remote connectivity
also manages nonconfigurable services such as enterprise bean and servlet life cycles, database connection resource pooling, data persistence, and access to the J2EE platform APIs

17. Container Types

18. J2EE Standard Services

19. J2EE Standard Services
JTA/JTS - demarcation interface used by container and components to demarcate transaction boundaries
RMI-IIOP - use of RMI-style programming
independent of underlying protocol supports both JRMP and CORBA IIOP
JavaIDL - allows components to invoke
external CORBA objects using IIOP
JDBC - standard API for accessing RDBMS
JMS - messaging that supports reliable P2P and publish-subscribe uses JAF

20. J2EE Standard Services
• JNDI - standard for accessing naming and directory services
• JavaMail - ability to send notifications
• JAXP - support for SAX and DOM parsing of XML documents and XSLT
• J2EE Connector Architecture – resource adapters that support access to EIS to be plugged in.
• JAAS - services to authenticate and enforce access controls upon users extends userbased authorization

21. Communication Technologies
 Internet protocols
 Remote method invocation protocols
 Object Management Group protocols
 Messaging technologies
 Data formats

22. Internet Protocols --Transport Control Protocol over Internet Protocol
 TCP/IP
--Transport Control Protocol over
Internet Protocol
 HTTP 1.0
--Hypertext Transfer Protocol
 SSL 3.0
--Secure Socket Layer

23. Remote Method Invocation Protocols
 A set of APIs that allow developers to build
distributed applications
 Uses Java language interfaces to define
remote objects
 Turn local method invocations into remote
method invocations

24. Object Management Group Protocols
 Java IDL
 RM I-IIOP

25. Messaging Technologies
 Java Message Service
point-to-point messaging
publish-subscribe messaging
 JavaMail

26. Data Formats GIF (Graphics Interchange Format)
 HTML 3.2
 Image files:
GIF (Graphics Interchange Format)
JPEG (Joint Photographic Experts Group)
 JAR file
 Class file
 XML

27. J2EE Platform Roles J2EE Product Provider Tool Provider
Application Component Provider
Application Assembler
Application
Deployer /System Administrator

28. J2EE Application Scenarios

29. Multitier Application Scenario

30. EJB-Centric Application Scenario

31. Web-Centric Application Scenario

32. J2EE Application Construction
Component Provider
Assembler
Deployer
IDE
Packaging
Tool
Portable
Deploy
Tool
Deployable
J2EE Server
Class
JSP
Java
HTML
Static
Create
Java
Code
EJB.JAR
Client.JAR
Web.WAR
Appl.EAR
EJB.JAR
Client.JAR
Web.WAR
Appl.EAR
Component
Provider
creates
compo-
nents 
Deployer
creates
deployable
units
and
deploys
them
into
servers
Authoring
J2EE Server
Assembler
creates
portable
packages
Create
Web
Contents

33. Packaging
Portability Limit
3 March 2001
SCM of J2EE

34. J2EE JAR files
Java ARchive file containing a J2EE module or application
EJB.JAR contains an EJB module
Web.WAR contains a Web module
Client.JAR contains a Client module
Application.EAR contains a J2EE application of one or more modules

35. Deployment and Deploy Tools
Changing/Add properties in the Deployment Descriptor
Access control
Bean references
External Resource references
Transactional attributes
Mapping Beans in to the Data Base
Deploy it into the server
Deploy Tools
J2EE compatible servers provides their own Deploy Tool

36. Deployment Deployable Deployable Web.WAR Application.EAR J2EE Server
WEB Server
J2EE Server
Deployable
Web.WAR
Deployable
Application.EAR
Deployment Tool
Vendor
Deployment
Descriptor
EJB Server
Client
Deployable
CLient.JAR
Deployable
EJB.JAR
Portable
Packages
Application.EAR
EJB.JAR
Web.WAR
Clientt.JAR