Transcript Micro Edition

Java 2 Micro Edition
Mano Chen
Senior Technical Consultant
Sun Microsystems
[email protected]
Computing Is Becoming Ubiquitous
Mainframe era
One computer, many users
PC era
One computer, one user
Consumer era
One user, many computers, and
these computers are networked
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A Game
What am I?
I have the following:
CPU
some memory
screen
keyboard
networked
runs applications
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Meet Your New Computers
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Agenda
Overview of J2ME
Developing J2ME Application
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Agenda
Overview of J2ME
Developing J2ME Application
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Problems
No software market !!!
Everything is proprietary
Hardware, software and tools
Handsets are useless without a
network
No compelling content
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J2ME is the Solution
Designed for small devices
Online and offline activities
Rich user and network interaction
models
Fully programmable
Portable
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Where Does J2ME Fit In?
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J2ME Configurations and Profiles
Java™ 2 Platform, Micro
Edition (J2ME™) encompasses
VMs and core APIs specified via
Configurations as well as vertical—
or market-specific—APIs specified
in Profiles
Optional
Packages
Optional
Packages
Java 2
Enterprise
Edition
(J2EE)
Core APIs
Java 2
Standard
Edition
(J2SE)
Core APIs
Personal
Profile
RMI
Profile
Other
CDC
Profiles
...
Foundation
Profile
Mobile Information
Device Profile
Java 2 Micro Edition Core APIs
Java
Card
APIs
Java Programming Language
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Java HotSpot
™
Java Virtual Machine (JVM)
KVM
Card VM
What Is a Configuration?
Defines the minimum capabilities and libraries
for a JVM that will be available on all devices
belonging to the same “horizontal” family of
devices
Similar requirements in memory size and
processing capabilities
Subject to compatibility test
Two configuration defined
Connected, Limited Device Configuration
Connected Device Configuration
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Connected Limited Device Configuration
Targeted at devices with
160KB to 512KB total memory available for
Java™ technology
Slow processor
Limited power (often battery)
Limited, perhaps intermittent connectivity to a
network (often wireless)
Extremely constrained UIs, small screens
CLDC 1.0 specification available for free
download now
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Sun provides CLDC reference implementation
built using the KVM
What Is a Profile?
A collection of Java technology-based
APIs that supplement a Configuration to
provide capabilities for a specific
“vertical” market or device type
Adds features that are specific to a
certain device category such as cell
phones or PDAs
One profile defined
Mobile Information Device Profile
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Mobile Information Device Profile
Targets mobile two-way communication
devices implementing J2ME CLDC
Profile addresses
Display toolkit, User input methods
Persistent data storage using simple
record-oriented database model
HTTP-based networking using CLDC
Generic Connection framework
MIDP 1.0 spec and implementation
available for download now
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CLDC and MIDP Architecture
MIDP Profile
Applications
OEM
Applications
MID Profile
CLDC (KVM)
Operating System
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OEM
APIs
MIDP Application Lifecycle
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Destroyed
destroyApp
startApp
Active
destroyApp
Start – acquire resources
and start executing
Pause – release resources
and become quiescent
(wait)
Destroy – release all
resources, destroy threads,
and end all activity
Pause
pauseApp
MIDP applications are
known as “MIDlets”
MIDlets move from state
to state in the lifecycle,
as indicated.
Typical J2ME Technology Stack
Your
MIDlet
Mobile
Information
Device
Profile
Yellow Pages, train
schedules and
ticketing, games…
UI, HTTP
networking...
J2ME core APIs
CLDC = KVM
+ J2ME Core
APIs
in this
example
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KVM
DSP chip
(e.g., ARM)
Threads, no Floats…
32-bit RISC, 256K
ROM, 256K Flash, 64K
RAM
MIDlet Suite
MIDlets are package as a JAR
MIDlets that are in the same suite can
access each others database
A descriptor file contains information
pertaining to the suite
Vendor name, version, size
Name of each MIDlet
Icons
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Application Loading Process
Advertise
App on
Web Page
User
Selects
App
JAM
Downloads
App
Web Page
(Name,
Version,
Size,
…)
Descriptor
File
Jar File
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Network Transfer
Java Application
Manager
J2ME Application Screenshots
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Agenda
Overview of J2ME
Developing J2ME Application
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J2EE Architecture
Client Tier
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Web Tier
Business Tier
Integration
Tier
EIS Tier
Key J2EE Components
Enterprise Java Bean
Business logic packaging, distribution and
access
Servlet
Java classes that extends the function of a
web server
Java Server Pages
Templates used to generate content
dynamically
J2EE Connectors
Generic access to back end EIS
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Example of A J2EE Application
EJB is used to encapsulate business logic
and apply them to EIS back office systems
Servlets are used to co-ordinate the
interactions between users and EJBs
JSPs are used to present forms, information
and results back to the user
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J2ME To J2EE Communication
J2EE Application Server
Web
Container
EJB
Container
J2ME
Servlet
forward
HTTP
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HTML
Servlet
Book
EJB
Handling J2ME Client
A request is made to the servlet
Process the request
Servlet determines if the type of client
Redirect to J2ME servlet for all J2ME
client communications
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Design Issues
Networking
Application messages
Working offline
Security
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Networking
J2ME side
Use HTTP 1.1 – requirement for all
MIDP devices
Use GET and POST communicating with
web tier
Client is responsible for HTTP headers
and data
J2EE side
Use servlet to handle client request
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MIDP Networking – Request
01 String url = “http://www.books.com/web/list?isdn=12345”;
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03 HttpConnection con = (HttpConnection)Connection.open(url);
04 con.setRequestMethod(HttpConnection.POST);
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06 con.setRequestProperty(“user-agent”, “CLDC-MIDP”);
07 con.setRequestProperty(“content-language”, “en”);
08 con.setRequestProperty(“content-type”
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, “application/x-www-form-encoded”);
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11 switch (con.getResponseCode( )) {
12
…
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MIDP Networking – Response
01 InputStream is = con.openInputStream();
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03 if (is.getType( ) != “application/mybook-encoding”)
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// Reject data stream
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06 byte buffer = new byte[256];
07 int size;
08 while ((size = is.read(buffer)) != -1) {
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// Do something with data
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11 is.close( );
12 // Display the data
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Servlet – Existing
01 public void doPost(HttpServletRequest req,
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HttpServletResponse res) … {
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// Looks up book
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String isdn = req.getParameter(“isdn”);
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if (req.getHeader(“user-agent”).equals(“CLDC-MIDP”) {
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RequestDispatcher rd = req.getRequestDispatcher(
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“MIDPcommunications”);
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rd.forward(req, res);
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return;
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}
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// Normal processing
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Servlet – MIDP Servlet
01 public void doPost(HttpServletRequest req,
02
HttpServletResponse res) … {
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res.setContentType(“application/mybook-encoding”);
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06
ServletOutputStream os = res.getOutputStream( );
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// Write data out
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os.flush( );
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Application Messages
Since 3G is NOT with us yet…
Conserve bandwidth
Send only the necessary data
Accommodate high latency
Send all required data in a single message
Use Gauge to provide progress indication
Message encodings
Use binary messages
Don’t use XML!!!
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Working Offline
MIDP supports record oriented database
Data can be stored locally on the CLDC
device
Information stored in local databases can
be manipulated
Need to implement data synchronization
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Security – Authentication
Build HTTP basic authentication into
MIDP application
GET /get_list.html HTTP/1.1
WWW-Authenticate: Basic realm=“fred”
Servlet Container
Authorization: Basic QWxhZGpbjpvcG…
01 if (con.getHeaderField(“www-authenticate”) != null) {
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String authString = Base64.encode(login + “:” + password);
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con.setRequestProperty(“authorization”, “basic “ + authString);
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if (con.getResponseCode() != HttpConnection.HTTP_OK) {
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// Do something …
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else
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Security – Authentication
Use JSP/Servlet form login
Use j_security_check method for
authentication
Required parameters are j_username
and j_password
01 String url = “http://www.books.com/web/j_security_check”;
02 url += “?j_username=“ + username;
03 url += “&j_password=“ + password;
04 HttpConnection con = (HttpConnection)Connection.open(url);
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06 con.setRequestMethod(HttpConnection.POST);
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Security – Secure Transport
HTTPS is not a requirement for MIDP
1.0
However…
Vendors are implementing them
J2ME for Palm supports HTTPS
HTTPS support targeted for MIDP-NG
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Summary
Designed for small handheld
devices
Easy to program
Works with J2EE
It’s real and its available now!!!!
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Getting Started on J2ME
Java2 Standard Edition
http://java.sun.com/j2se
Java2 Micro Edition Wireless Toolkit
http://java.sun.com/products/j2mewtoolki
t/
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Thank You
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