Transcript Finance End User Skeleton

Developing and Deploying
Java Applications for
BlackBerry
Making Sense of it All
Eric Giguère
Senior Software Architect
[email protected]
Overview
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Understanding J2ME in general
The BlackBerry perspective on J2ME
Gathering the necessary pieces
Programming tips
Moving beyond the BlackBerry
About iAnywhere
iAnywhere is the acknowledged leader in mobile
databases, mobile middleware, and mobile
management
About Eric
• Practicing software developer, extensive
experience with mobile platforms and with all kinds
of Java-based technology
• Author of three books, including the first book on
Java 2 Micro Edition -- over 5 years of J2ME!
Don’t buy these, they’re
way out of date!
A Question
Q: Why did the chicken cross the road?
A: She was too busy browsing her AvantGo channels
on her BlackBerry.
Point your BlackBerry Browser to:
rim.avantgo.com
At the Sybase Booth
• Visit the Sybase booth in the Solutions Showcase
for a demonstration of the new MobiLink Client API
– Sync relational data down to the device and back
• SQL Server, Oracle, DB/2, ASE, SQL Anywhere
– Ask for Liam
– Or talk to me after the session (my code)
Understanding J2ME
Understanding J2ME
• Java 2 Micro Edition (J2ME) is an umbrella term for
a set of Java technologies created to run Java on
less capable devices
• Key concepts of configurations, profiles and
optional packages:
– configuration = VM + runtime classes (horizontal)
– profile = domain-specific classes for building standalone
applications (vertical)
– optional package = domain-specific classes that expose
specific functionality but not applications (horizontal or
vertical)
Configurations
• Only two configurations defined:
– Connected Limited Device Configuration (CLDC)
– Connected Device Configuration (CDC)
• CLDC is a stripped-down VM and runtime
environment
– no finalization, no reflection, only a few classes
– CLDC 1.0 didn’t even support floating-point
• CDC is a superset of CLDC
– full language and VM support
– a much broader set of standard Java 1.3 classes
Profiles
• Profiles built on the CLDC:
– Mobile Information Device Profile (MIDP)
– Information Module Profile (IMP)
• “Headless” MIDP (no UI)
• Profiles built on the CDC:
– Foundation Profile
– Personal Basis Profile
• Built on top of Foundation Profile
– Personal Profile
• Build on top of Personal Basis Profile
• The transition profile for the old PersonalJava
Optional Packages
• Many released or in development, some examples:
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PIM Optional Package
File Connection Optional Package
Wireless Messaging API
Mobile Media API
• Problem: not every device supports every optional
package
Who Does All Of This?
• All J2ME standards are developed using the Java
Community Process (JCP) using formal Java
Specification Requests (JSRs)
• JSRs developed by an expert group (EG)
representing the J2ME community at large
• RIM is on the EGs for several of the important
standards
• For more info, see http://www.jcp.org
The BlackBerry Perspective
BlackBerry and J2ME
• BlackBerry devices (Java-based) run MIDP and
CLDC
– MIDP 1.0/CLDC 1.0 for 3.6/3.7 devices
– MIDP 2.0/CLDC 1.1 for 3.8/4.0 devices
– Custom Java VM
• Additional APIs available
– Some optional packages
– Many BlackBerry-specific APIs (vendor extensions)
• Built-in apps written in Java
– RIM eats it’s own food
Application Models
• MIDlets
– Applications built using MIDP application lifecycle and
user interface classes
– Portable to other platforms unless BB APIs used
• BlackBerry applications
– Standard “public static void main( String[] args )” entry
point
– Tied to BlackBerry, but more control over the application
– BlackBerry-specific UI classes
– Can run in background (no UI), on startup, etc.
How Applications Are Built
• Classes are compiled as usual
• CLDC requires a separate preverification step
• Output then transformed using RIM tools into a
.COD file that can be installed on the device
• Applications can be loaded directly through
BlackBerry Desktop Manager, the javaloader tool,
or wirelessly via over-the-air (OTA) provisioning
How Applications Are Built
• Standard tool is the Java Development
Environment (JDE)
– integrated editor, debugger
• Can also use Ant with Antenna tasks
– See http://antenna.sourceforge.net
• Eclipse also possible using Ant+Antenna
– Getting the classpaths right can be tricky
– See http://eclipseme.org for the EclipseME project
BlackBerry APIs
• Rich set of BlackBerry-specific classes
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Utility classes to deal with missing J2SE classes
Different UI model than MIDP
Encryption classes
A persistent object model loosely patterned on Java
serialization
– More communication protocols, not just HTTP
– Many APIs require your app to be signed
Gotchas
• Occasionally classes are documented but not
implemented until someone pesters RIM
• Only documentation is from RIM
– Javadocs needs some work, lacking many details
– The only BlackBerry books available so far are about
using the device or making blackberry wine.
• But at least one BlackBerry programming book is coming
• Pester RIM for better docs and tool enhancements!
Gathering the Necessary Pieces
Getting Started
• Download the JDE from http://www.blackberry.com
– Versions for 3.7 or 4.0
– If you’re going to target 3.6 or 3.7, use JDE 3.7
– You’ll also need Java SDK 1.4.2
• http://java.sun.com/j2se/1.4.2/download.html
• New to Java? Find some old books
– Ideally covering Java 1.1, not 1.2 or higher
• You won’t get seduced by all the new classes, especially new
1.5 features like generics and enums
• But important concepts like inner classes are covered
Do You Need a BES?
• RIM ISV partners can purchase a BES for
development purposes
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useful for testing apps
can enable things that corporate BES disallows
and for understanding how things are done
IT may raise concerns
not that easy to setup
• don’t forget a mail server is required
• Exchange needs its own NT domain
Code Signing
• Most “interesting” APIs protected, app won’t run on
device without being signed
– But you can run them in the simulator
• Signing requires certificates obtained from RIM
– Small fee ($100) involved
– Certificates needed for each build machine
• Signing is an online-only process
– Communicates back to RIM
– Certificate owners gets email every time
Programming Tips
Reduce, Reuse, Recycle
• Don’t create lots of objects
– Garbage collection eats up CPU time
– Can run out of object handles
• Look for opportunities to reuse objects
– Invariant classes good in theory, but more realistic to
allow changes
– Remember arrays are objects!
Use Threads
• Always do I/O operations on an application-defined
thread
– Don’t block the system event thread
• Not only slows things down, but may also cause the app to
freeze as system tries to prompt user for permission
– Java threading mechanisms are quite good
• Take the effort to learn them
• Good book is Concurrent Programming in Java by Doug Lea
Keep Applications Small
• Don’t go overboard with inner and nested classes
• Think carefully about class interactions and
dependencies
• Can you get away with using a built-in class instead
of your own?
HTTP or Sockets?
• If you’re using MDS, sockets are a great option
– Can also open a server socket and listen for data to be
pushed to your app
– Extra complexity of defining your own protocol
• For non-MDS, HTTP is the best
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Easier to get through the firewall
Support varies greatly by carrier, though
HTTPS may also be available
Easy to write servlet that shares the same data classes
(Java on both ends)
Start the MDS Simulator!
• If you’re doing network I/O, remember to start the
MDS simulator before you run your app in the
device simulator
Moving Beyond the BlackBerry
• Non-BlackBerry J2ME devices becoming more
powerful
– Still mostly consumer-oriented
– In the future, more will be running the BlackBerry
environment (BlackBerry Built-In) as well
• Your BlackBerry apps will work on BlackBerry Built-In without
any changes
• Things you take for granted in an MDS environment
are not there
– Have to get through the firewall
– Not as secure
MIDP-Only Is One Option
• You can write an application that only uses APIs
from MIDP and perhaps an optional package or two
• Application gets packaged as JAR file and an
accompanying JAD file
• Will run on most J2ME-enabled cellphones
– Except that there are many buggy implementations
Other Option: Split the Source
• Alternatively, build two different apps, one for
BlackBerry, one for MIDP
• Split code into three parts
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One common (no BlackBerry APIs, no user interface)
One for BlackBerry
One for MIDP
More complex code due to use of factories and more
interfaces and abstract classes
Q&A