Server side architecture

1

• The 21th century Repairman
• Agenda
• Introduction
• J2EE
• J2ME
• Demonstration

2
Goal of the project

• The purpose of this project is
• To get some experience with J2EE
• Investigate some of the possibilities with J2ME
• Build a semi-large distributed system

3
Pervasive Repairer
We ended up with a system intended to support
situated and distributed work of a repairer, who
is working with large technological systems.
4
System overview
Customers place
The repair company
Subcontractor companies
Administrative clerk
The situated repairer
Vendor
Vendor
Vendor
XML
SOAP
XML
Http
CompanyServer (J2EE)
Http
XML
Subcontractor Manager
DB
Interactive web services
5
Model
6
Server side architecture
Presentation Layer (Servlet/JSP)
Web
J2ME
FLAF / HTTP
Business Layer (Session Beans)
HTML / HTTP
Value Objects
Model Layer (Entity Beans)
Container Managed Persistence
DB
7
Session beans
8
J2ME

• CLDC, MIDP 1.0, KVM
• MIDlets. Life cycle.
• MIDP/CLDC API. No interface, high-level GUI.
• Core packages java.io, java.lang, java.util,
• Packages javax.microedition.io, .midlet, .rms,
  lcdui
• Application development.
• J2ME Wireless Toolkit Network monitor, Output
  window, Debugger, Memory monitor, Profiler.
• IBM J9 CLDC- and MIDP-compliant Java Virtual
  Machine

9
J2ME platform

• Profiles software application issues
• Configurations hardware issues

10
J2ME Client Application
11
Client(J2ME)-server interaction

• Client a wireless, handheld device (cell phone,
  PDA)
• Limited resources (memory, CPU), limited
  connection bandwidth, reduced facilities for user
  interaction, etc. etc
• Challenges
• Minimize number of request-responses
• Minimal amount of data sent per response
• On the server side minimize number of requests
  to session beans
• Do as much data processing as possible
  server-side

12
Client-server interaction II

• A collection of Java Servlets translate value
  objects, supplied by session beans, to flat
  strings of data
• Data transmitted to J2ME client in HTTP headers
  eases parsing on the client side
• This defines a protocol for sending data to J2ME
  client

13
Client-server interaction III

• Lists of objects (e.g. product types, orders) -
  the client requests a specific part of the list
  detailed data only sent upon request
• Session tracking implemented (unable to use
  javax.servlet.http.HttpSession with J2ME client)
• Thread-safety

14
Deployment whats in it?

• IBM WebSphere, Device Developer
• Create MIDlet suite
• Install and run application Run on handheld
  target device
• iPAQ
• Install VM copy files from workstation to iPAQ
• Install Wireless communication card driver from
  workstation.

15
Evaluation J2EE

• Advantages
• A lot is granted Transaction, Scalability
• Disadvantages
• Hard to understand errors (combination of
  deployment description and Code)
• Immature tools. Bugs, User Interfaces not always
  intuitive.