Overview of J2EE

1
Overview of J2EE

• Distributed Multitiered Applications

2
What Well Cover

• Distributed Multitiered Applications
• J2EE Components
• J2EE Clients
• Web Components
• Business Components
• Enterprise Information System Tier

3
Distributed Multitiered Applications

• Application logic divided into components
  according to function
• Components installed on machines according to
  tier
• J2EE considered three tier three locations
• Place multithreaded application server between
  client and back-end

4
Two examples
5
J2EE Components

• a self-contained functional software unit that is
  assembled into a J2EE application with its
  related classes and files and that communicates
  with other components
• 3 types app clients/applets, servlets/jsps,
  EJBs
• Standard Java classes assembled into J2ee
  applications and deployed to J2EE server

6
J2EE Clients

• Web Clients web pages generated by web
  components in the web tier and browser thin
  client
• Applets Java programs executed in JVM in
  browser
• J2EE Application Clients
• JavaBeans manage data flow not J2EE components

7
Example J2EE Server Communication

• Client communicates directly or through
  JSP/Servlet
• Trade-offs
• Thin client easier to distribute, deploy and
  manage
• Thick client better user experience

8
Web Components

• Servlets Java classes that process requests
  (usually HTTP) and generate responses
• JSPs text based documents that execute as
  servlets
• Static HTML/Applets assembled with Web components
  but not part of J2EE Web components

9
Business Components

• Meets the needs of a particular business domain
• Not presentation logic rules of what data is
  available, not how it is displayed
• What data may be changed according to what rules,
  not what the screen looks like

10
Example Business Tier
11
Enterprise Information Tier

• Enterprise Infrastructure System/software
• Enterprise Resource Planning (ERP) (like
  PeopleSoft, JD Edwards, etc)
• Mainframe transactions
• Database Systems

12
What We Covered

• Distributed Multitiered Applications
• J2EE Components
• J2EE Clients
• Web Components
• Business Components
• Enterprise Information System Tier

13
Overview of J2EE

• J2EE Containers

14
What Well Cover

• Why Containers?
• Container Services
• Container Types
• Packaging

15
Why Containers

• Thin client multi-tiered applications can be very
  complex
• Transactions
• State Management
• Multithreading
• Resource Pooling
• Other low level details (interaction with server
  resources)
• J2EE Containers provide these services

16
Container Services

• Container interface between Components and
  low-level services
• Assembly process specifies container settings for
  the J2EE application
• Highlights security model, transaction model,
  JNDI, Remote connectivity
• Same application behaves differently on different
  servers
• Non-configurable services, life-cycle, connection
  pooling, etc.

17
Container Types

• J2EE Server EJB and Web containers
• EJB container
• Web container
• Application Client container
• Applet Container

18
J2EE Containers
19
Packaging

• EAR files assemble components
• J2EE Module 1 or more J2EE components
  descriptor
• Deployment descriptor xml that describes
  deployment settings
• EJB modules jar file with EJB classes DD
• Web modules war file with JSPs, servlets,
  images, etc DD
• Resource Adaptor modules rar file with DD
• Application client modules

20
What We Covered

• Why Containers?
• Container Services
• Container Types
• Packaging

21
Web Services Support

• Web based enterprise applications

22
What Well Cover

• Extensible Markup Language
• HTTP-SOAP Transport Protocol
• WSDL Standard Format
• UDDI and ebXML Standard Formats

23
Extensible Markup Language

• cross-platform, extensible, and text-based
  standard for representing data
• Create own tags/stylesheets
• Example company price lists
• Translate to html for web
• Create a marketing presentation
• Read into an app for processing

24
HTTP-SOAP Transport Protocol

• Simple Object Access Protocol running over HTTP
  connections
• Completely interoperable exchange clients,
  webservices, platforms, locations
• XML based protocal that follows HTTP
  request/response model
• The SOAP portion provides XML-based
• Envelope to describe message and how to process
• Encoding rules for app-defined data types
• Convention for representing request/response

25
WSDL Standard Format

• XML format for describing network services
• Provides
• Name of Service
• Location of Service
• How to communicate with the service
• Published on Web or in UDDI registry
• J2EE has tool for generating WSDL

26
UDDI and ebXML Standard Formats

• Universal Description, Discovery, and Integration
  (UDDI)
• www.uddi.org
• a "meta service" for locating web services by
  enabling robust queries against rich metadata
• Electronic Business using eXtensible Markup
  Language
• www.ebxml.org
• Modular suite of specs for message
  exchange/business processes

27
What We Covered

• Extensible Markup Language
• HTTP-SOAP Transport Protocol
• WSDL Standard Format
• UDDI and ebXML Standard Formats

28
Development Roles

• Different people can perform different parts of
  the process

29
What Well Cover

• J2EE Product Provider/Tool Provider
• Application Component Provider
• Application Assembler
• Application Deployer and Administrator

30
J2EE Product Provider/Tool Provider

• Reusable modules make it possible to divide
  dev/deployment into roles
• Product provider - platform, APIs, and other
  features defined in the J2EE specification
  usually OS, RDBMS, App server providers
• Tool Provider - development, assembly, and
  packaging tools used by component providers,
  assemblers, and deployers.

31
Application Component Provider

• Enterprise Bean Developer
• Writes and compiles the source code
• Specifies the deployment descriptor
• Bundles the .class files and deployment
  descriptor into an EJB JAR file
• Web Component Developer
• Writes and compiles servlet source code
• Writes JSP and HTML files
• Specifies the deployment descriptor for the Web
  component
• Bundles the .class, .jsp, .html, and deployment
  descriptor files in the WAR file
• J2EE Application Client Developer
• Writes and compiles the source code
• Specifies the deployment descriptor for the
  client
• Bundles the .class files and deployment
  descriptor into the JAR file

32
Application Assembler

• receives application component JAR files from
  component providers and assembles them into a
  J2EE application EAR file.
• Specifies the deployment descriptor for the J2EE
  application
• Verifies that the contents of the EAR file are
  well formed and comply with the J2EE specification

33
Application Deployer and administrator

• Administers network/oversees runtime
• sets transaction controls, security attributes,
  DB connections
• Installs/configures applications
• Puts EAR file on server
• Modifies DD as necessary
• Verifies well-formed EAR
• Installs Applications

34
What We Covered

• J2EE Product Provider
• Tool Provider
• Application Component Provider
• Application Assembler
• Application Deployer and Administrator

35
J2EE APIs

• The pieces that make it work

36
What Well Cover

• JDBC API
• Java Servlet Technology
• JavaServer Pages Technology
• Java Message Service
• Java Naming and Directory Interface
• Java Transaction API
• JavaMail API
• JavaBeans Activation Framework

37
What Well Cover (continued)

• Java API for XML Processing
• Java API for XML Registries
• Java API for XML-Based RPC
• SOAP with Attachments API for Java
• J2EE Connector Architecture
• Java Authentication and Authorization Service
• Simplified Systems Integration

38
JDBC

• JDBC invoke SQL commands from Java
• Use for bean-managed persistence, Session bean
  access to DB or from servelet/JSP
• Not necessary for CMP
• Two parts application level interface (standard
  api) and Service Provider Interface (to attach
  drivers)

39
Servlets/JSPs

• Extend server capabilities through
  request/response
• Most often used to extend Web applications
• JSPs allow servlet code to be placed in text
  based files (html, xml, wap, etc).

40
JMS

• JMS is the Java MOM
• Topics and Queues
• Queues are point to point
• Topics are publish/subscribe
• Durable subscribers
• Specification of Queues or Topics

41
JNDI

• Java Naming and Directory interface
• methods for performing standard directory
  operations, such as
• associating attributes with objects
• searching for objects using their attributes
• store and retrieve any type of named Java object.
  
• InitialContext looks up in servers naming
  context - javacomp/env
• Store DataSource, EJB, etc references
• JNDI can access multiple naming/directory
  services
• Can access LDAP, DNS, etc.

42
JTA/Java Main/Activation

• Java Transaction API standard interface for
  demarcating transactions
• J2EE provides default autocommit, but can use JTA
  to keep transaction open across DB calls
• Java Mail to send emails
• JavaBeans Activation Framework - used by Java
  Mail
• Determine type of data
• Encapsulate it
• Discover operations on it
• Provide correct Java beans for using it

43
JAXP

• Java API for XML Processing (JAXP)
• Supports Document Object Model (DOM), Simple API
  for XML parsing (SAX) and XML Stylesheet Language
  Transformation (XSLT)
• Independent of XML processing implementation
• Provides namespace support work with schemas
  that might have conflicts.

44
Java API for XML Registries (JAXR)

• access business and general-purpose registries
  over the Web.
• supports the ebXML Registry/Repository standards
  and UDDI specifications
• Single API to access both
• Can use to access schemas stored in registries

45
Java API for XML-based RPC (JAX-RPC)

• Uses SOAP and HTTP so clients can make RPC calls
  over the internet
• Also supports WSDL
• Can use Secure Socket Layer (SSL) and Transport
  Layer Security (TLS) protocols to establish basic
  or mutual authentication.

46
SAAJ

• SOAP with Attachments API for Java (SAAJ)
• low-level API upon which JAX-RPC depends
• enables the production and consumption of
  messages that conform to the SOAP 1.1
  specification and SOAP with Attachments
• Developers will probably use JAX-RPC

47
J2EE Connector Architecture

• A resource adapter is a software component that
  allows J2EE application components to access and
  interact with the underlying resource manager.
• Resource adapters are specific to resource
  managers
• typically different resource adapter for each
  type of enterprise information system.

48
JAAS

• Java Authentication and Authorization Service
  (JAAS)
• J2EE applications can authenticate and authorize
  user or user groups.
• Based on Pluggable Authentication Module (PAM)
  framework

49
Simplified Systems Integration

• J2EE APIs enable integration through
• Unified application model across tiers
• Simplified response and request with JSP 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

50
What We Covered

• JDBC API
• Java Servlet Technology
• JavaServer Pages Technology
• Java Message Service
• Java Naming and Directory Interface
• Java Transaction API
• JavaMail API
• JavaBeans Activation Framework

51
What We Covered (continued)

• Java API for XML Processing
• Java API for XML Registries
• Java API for XML-Based RPC
• SOAP with Attachments API for Java
• J2EE Connector Architecture
• Java Authentication and Authorization Service
• Simplified Systems Integration