Komponentbasert utvikling
Den sanne objektorientering
Trygve Reenskaug
Numerica Taskon
UML
Unified Modeling Language
og
komponentbasert utvikling
Geilo 19 april 1999
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:05 AM.
Personal Information Environments
Content and Communication
Digital
Map
Census
Data
Police
Records
House
Drawings
Police
Dispatcher
Komponentbasert utvikling
© Trygve Reenskaug 1999
Aerial
Photos
5/29/2016 3:32:06 AM.
Presentation Plan
• The Communication-Centered Paradigm
• Building Systems with Components
• But the Real Challenge is …
Summary and conclusion
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:07 AM.
CPU-Centered
paradigm
Output
Input
Central
Processing
Unit
FORTRAN
Algol 60
Tape
Software
Hardware
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:07 AM.
Storage-Centered
paradigm
Input
App.1
Output
Shared
database
Central
Processing
Unit
Memory
App.3
Tape
Disk
App.4
DB Schema language
e.g. Entity-Relation
e.g. NIAM
Software
Hardware
Komponentbasert utvikling
App.2
© Trygve Reenskaug 1999
5/29/2016 3:32:08 AM.
Communication-Centered
Output
Tape
Central
Processing
Unit
Object 1
Disk
Object 3
Information Bus
Input
Communication Bus
paradigm
Object 2
Object 4
Memory
Composition language
e.g. Object Constraint Language
Hardware
Komponentbasert utvikling
Software
© Trygve Reenskaug 1999
5/29/2016 3:32:08 AM.
No Main Program!
The SYSTEM
Centralized solutions
The designer
• sees everything
• knows everything
• understands everything
• controls everything
Distributed solutions
The object
- has responsibility
- knows its collaborators
- is robust
Nobody knows everything!
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:08 AM.
Advantages
Communication-Centered paradigm
• Unlimited Scaling
• Distributed Ownership
• Support people’s Tasks
• Flexible Consistency Requirements
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:08 AM.
Presentation Plan
• The Communication-Centered Paradigm
• Building Systems with Components
• But the Real Challenge is …
Summary and conclusion
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:09 AM.
App. for booking meeting rooms
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:09 AM.
We use objects
to master the age of distribution
Object-B
IN
IN
OUT-B
OUT-C
OUT-C
Methods Variables
Object-C
Methods Variables
IN
Object-A
Methods Variables
Message
triggers method
causes response
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:09 AM.
What is a Component?
• A Component is a reusable object
• A Component is an object playing
standardized roles in a specified
container
• A component is reused by cloning
• Tools are used to compose systems
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:09 AM.
Component Value Chain
Application Assembler
(User expert)
Component Deployer
(Operational environment expert)
Component Provider
(Domain expert)
Component Container Provider
(System programmer)
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:09 AM.
The competing technologies
CORBA™ Object Management Group (OMG)
Public standards
Java™
SUN Microsystems
Build once, run anywhere
COM™
Microsoft
Dominating on desktops
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:10 AM.
Java Bean
• User Interface
• Properties
• Events
• Composition
• Run time context
Information Bus
Component standardization
examples
Enterprise Java Bean
• Naming
• Persistence
• Transactions
• Security
• Load sharing
• Run time context
Client
Komponentbasert utvikling
Server
© Trygve Reenskaug 1999
5/29/2016 3:32:10 AM.
Compose User Interface
with Java Beans
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:10 AM.
The Enterprise Java Bean objects
and their message paths
WEB
Browser
Information Bus
Booking
Client
Name
Server
Booking
Home
Room
Chooser
Booking
Bean
Booking
Object
4: getRooms();
Multithreading
Reuse EJBs
Reuse DB conn.
Persistence
Could be Entity Bean
java.sql.
Connection
5: getRooms();
Session Bean
Transactions
Security
Java Bean
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:10 AM.
EJB Implementation
We wrote:
• BookingHome.java
Intf. Client create its own server object
• Booking.java
Intf: Client access booking service
• BookingBean.java
Class: The booking business logic program itself
• BookingClient.java
Class: The main user interface class
The IONA EJBHome tool created these files for us:
• RoomBroker.ejbml
• datasource.properties
• ejbhome.properties
• Iona*.java/class
Komponentbasert utvikling
Property file describing the booking EJB
File: Maps datasource names
to JDBC databases URLs.
File: EJB Server configuration
Class: A number of supporting java classes
© Trygve Reenskaug 1999
5/29/2016 3:32:15 AM.
Presentation Plan
• The Communication-Centered Paradigm
• Building Systems with Components
• But the Real Challenge is …
Summary and conclusion
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:15 AM.
Distributed Systems
What you get:
• Unlimited scaling
• Distributed ownership
• Specific task support
• Information partitioning
How you do it:
• Think in terms of objects, their
responsibilities and collaboration.
• Think in terms of open systems, no
main program.
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:15 AM.
Component-based development
What you get:
• Build by composing library objects,
avoid coding.
• Leverage infrastructure mechanisms
(transactions, security, persistence,…)
How you do it:
• Think in terms of objects.
(Responsibilities, environment, collaboration.)
• Penetrate vendor fog - find essentials
• Insist on high product quality
• Adapt to new layers in value chain
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:15 AM.
The main problems
We spend too much time and effort
on low-level mechanics.
Current offerings are NOT:
• Easy and intuitive to use
• Smooth development platforms
• Reliable
• Secure
• Extensible
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:16 AM.
The Real Challenges
The
Connected
Organization
Business
processes
Komponentbasert utvikling
Effective,
Enjoyable
and
Instructive
Tools
Task / Use Case / Tool
© Trygve Reenskaug 1999
Effective
Partitioning
of
Information
Services
Information services
5/29/2016 3:32:16 AM.
Distributed systems
Do it!
http://www.ifi.uio.no/~trygve
Komponentbasert utvikling
© Trygve Reenskaug 1999
5/29/2016 3:32:17 AM.