Developing and Deploying Java Applications for BlackBerry

1
Developing and Deploying Java Applications for
BlackBerry

• Making Sense of it All

Eric GiguèreSenior Software Architectgiguere_at_ian
ywhere.com
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Overview

• Understanding J2ME in general
• The BlackBerry perspective on J2ME
• Gathering the necessary pieces
• Programming tips
• Moving beyond the BlackBerry

3
About iAnywhere

• iAnywhere is the acknowledged leader in mobile
  databases, mobile middleware, and mobile
  management
  

4
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!

Dont buy these, theyre way out of date!
5
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
  torim.avantgo.com

6
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)

7
Understanding J2ME
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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)

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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 didnt 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

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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

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Optional Packages

• Many released or in development, some examples
• PIM Optional Package
• File Connection Optional Package
• Wireless Messaging API
• Mobile Media API
• Problem not every device supports every optional
  package

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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

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The BlackBerry Perspective
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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 its own food

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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.

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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

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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 AntAntenna
• Getting the classpaths right can be tricky
• See http//eclipseme.org for the EclipseME project

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BlackBerry APIs

• Rich set of BlackBerry-specific classes
• 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

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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!

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Gathering the Necessary Pieces
21
Getting Started

• Download the JDE from http//www.blackberry.com
• Versions for 3.7 or 4.0
• If youre going to target 3.6 or 3.7, use JDE
  3.7
  
• Youll 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 wont get seduced by all the new classes,
  especially new 1.5 features like generics and
  enums
  
• But important concepts like inner classes are
  covered

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Do You Need a BES?

• RIM ISV partners can purchase a BES for
  development purposes
  
• 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
• dont forget a mail server is required
• Exchange needs its own NT domain

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Code Signing

• Most interesting APIs protected, app wont 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

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Programming Tips
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Reduce, Reuse, Recycle

• Dont 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!

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Use Threads

• Always do I/O operations on an application-defined
  thread
  
• Dont 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

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Keep Applications Small

• Dont 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?

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HTTP or Sockets?

• If youre 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
• 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)

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Start the MDS Simulator!

• If youre doing network I/O, remember to start
  the MDS simulator before you run your app in the
  device simulator

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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

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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

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Other Option Split the Source

• Alternatively, build two different apps, one for
  BlackBerry, one for MIDP
  
• Split code into three parts
• 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
  

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Q A