1. Programming Handheld and Mobile devices 1 Programming of Handheld and Mobile Devices Lecture 10 Java for MIDs Rob Pooley rjp@macs.hw.ac.uk

2. Programming Handheld and Mobile devices 2 Java 2 Platform, Micro Edition (J2ME) The Java 2 Platform, Micro Edition (J2ME) provides a flexible environment for applications running on consumer devices, such as mobile phones, PDAs, and TV set-top boxes, as well as a broad range of embedded devices. J2ME includes Java virtual machines and a set of standard Java APIs It includes flexible user interfaces, a robust security model, a broad range of built-in network protocols, and extensive support for networked and offline applications

3. Programming Handheld and Mobile devices 3 The J2ME Architecture The J2ME architecture comprises a variety of configurations, profiles, and optional packages that implementers and developers can choose from

4. Programming Handheld and Mobile devices 4 J2ME Configurations and Profiles Even within J2ME one size does not fit all Configurations: Minimum libraries and JVM Profiles: libraries for specific devices or markets J2ME configurations –CLDC –CDC J2ME profiles MIDP –Foundation, Bluetooth, Personal,... Configurations and profiles defined by the Java Community ProcessSM

5. Programming Handheld and Mobile devices 5 Configurations Configurations comprise –a virtual machine –a minimal set of class libraries. They provide the base functionality for a particular range of devices that share similar characteristics, such as network connectivity and memory footprint. Currently, there are two J2ME configurations: –the Connected Limited Device Configuration (CLDC) Established and widely used –the Connected Device Configuration (CDC) Next generation configuration

6. Programming Handheld and Mobile devices 6 Profiles To provide a complete runtime environment for a specific device category a configuration must be combined with a profile This is a set of higher-level APIs that further define the application life-cycle model, the user interface, and access to device-specific properties. A profile supports a narrower category of devices within the framework of a chosen configuration. A widely adopted example is to combine CLDC with the Mobile Information Device Profile (MIDP) to provide a complete Java application environment for cell phones and other devices with similar capabilities

7. Programming Handheld and Mobile devices 7 Optional Packages The J2ME platform can be extended by adding various optional packages to a technology stack that includes either CLDC or CDC and an associated profile. Optional packages offer standard APIs for using both existing and emerging technologies such as database connectivity, wireless messaging, multimedia, Bluetooth, and web services. Because optional packages are modular, developers can avoid carrying the overhead of unnecessary functionality by including only the packages an application actually needs.

8. Programming Handheld and Mobile devices 8

9. 9 Mobile Information Device Profile The first J2ME profile Targets devices implementing CLDC Profile addresses: –Display toolkit, user input methods –Persistent data storage –Messaging( SMS, email, etc), security and networking over wireless network connection

10. Programming Handheld and Mobile devices 10 Related Technologies: Java Card™ Technology Specifies minimized subset of Java technology for GSM SIM cards, smart cards, Java rings, and other extremely constrained devices Key benefits versus non-Java smart cards –Multiple applications per card –Post-issuance updates to apps on card

11. Programming Handheld and Mobile devices 11 Related Technologies: EmbeddedJava™ Technology EmbeddedJava. technology is a program from Sun supporting development of dedicated-function embedded devices for a wide range of end uses EmbeddedJava technology gives device manufacturers the ability to: –Configure the Java platform to leave out unneeded classes and VM features –Minimize resource requirements and cost for a deeply-embedded device –Optimize for devices with no GUI and intermittent (at best) networking –Keep APIs for their devices private

12. Programming Handheld and Mobile devices 12 J2ME™: Connected Device Configuration Connected Device Configuration (CDC) –Targeted for devices that have 2 MB or more total available memory –Memory dedicated to J2ME environment –More than 2MB ROM/Flash –More than 512 KB RAM –Network connectivity –Full Java 2 Virtual Machine specification

13. Programming Handheld and Mobile devices 13 Example J2ME™ CDC Uses Wireless communicators High-end PDAs TV set-top boxes Gateways Automotive entertainment and navigation systems Telecomm/Networking Equipment Industrial Controllers

14. Programming Handheld and Mobile devices 14 What Is CVM? Basis for J2ME CDC and profiles –Large VMs for desktops/servers don.t scale well to devices –Static and dynamic memory footprint too big –Not embeddable, ROMable, not portable –Implicit assumption of virtual memory –Native stack use, address range reservation –Implicit assumption of process model Global variables,.system threads.

15. Programming Handheld and Mobile devices 15 CVM features Good JVM features Device friendliness. Easily re-targetable Narrow porting interface Almost entirely in C (except dynamic compiler) ~256KB with JNI, reflection, verification,. CVM supports all Java 2 Platform, version 1.3, VM features and libraries for security, weak references, JNI, RMI and JVMDI CVM allows devices to map Java threads directly to native threads. Can run Java classes out of ROM Contains a precise memory system with advanced Garbage Collection features: Small average GC pause times Pluggable Garbage Collectors Full separation of VM from memory system

16. Programming Handheld and Mobile devices 16 J2ME Profiles Mobile Information Device Profile (MIDP) –Profile for wireless devices implementing CLDC J2ME Foundation Profile –Profile for non-GUI networked devices implementing CDC J2ME Personal Basis, Personal, RMI Profiles –Basic graphics, next generation PersonalJava environment, and RMI support for CDC & Foundation Profile based devices

17. Programming Handheld and Mobile devices 17 CDC APIs Defines minimum set of APIs for Java VM support –java.lang VM system classes (Object, Thread, etc.) –java.util.Underlying utilities –java.net.UDP Datagram and File URL –java.io.File –java.text.I18n support for Java VM error messages –java.security.Fine grain security and encryption for object serialization

18. Programming Handheld and Mobile devices 18 CVM Sizes Today CVM only –Static ROM + RAM req.= 258 KB Natives only –Static ROM + RAM req.= 124 KB Porting layer only –Static ROM + RAM req.= 28 KB CVM+natives+porting_layer –Static ROM + RAM req.= 410 KB

19. Programming Handheld and Mobile devices 19 Foundation Profile APIs Defines core set of Java platform functionality –No GUI –Subset of JDK 1.3 Completes full functionality from CDC –java.lang.Rounds out full java.lang.*(Compiler, UnknownError) –java.util.Adds full zip support, Timer, etc. –java.net.Adds TCP Socket and HTTP –java.io.Rounds out full java.io.* (Readers and Writers) –java.text.Full I18n (Annotation, Collator, Iterators, etc.) –java.security.Adds Code Signing and Certificates

20. Programming Handheld and Mobile devices 20 CVM Sizes with Foundation Profile APIs CDC Java libraries (ROMized) –Static ROM + RAM req.= 1011 KB Foundation Java libraries (ROMized) –Static ROM + RAM req.= 1564 KB CDC TOTAL (CVM+natives+porting+libraries) –Static ROM + RAM req.= 1421 KB Java libraries + natives for Foundation Profile –Static ROM + RAM req = 553 KB Foundation TOTAL (CVM+natives+porting+libraries) –Static ROM + RAM req.= 1974 KB