Java 2 Micro Edition (J2ME) and the world of java

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Java 2 Micro Edition (J2ME) and the world of
java

• 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

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The J2ME Architecture

• The J2ME architecture comprises a variety of
  configurations, profiles, and optional packages
  that implementers and developers can choose from

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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

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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

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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

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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.

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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

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Related TechnologiesJava 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

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Related TechnologiesEmbeddedJava 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

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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

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Example J2ME CDC Uses

• Wireless communicators
• High-end PDAs
• TV set-top boxes
• Gateways
• Automotive entertainment and navigation systems
• Telecomm/Networking Equipment
• Industrial Controllers

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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.

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CVM features

• 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

• Good JVM features
• Device friendliness.
• Easily re-targetable
• Narrow porting interface
• Almost entirely in C (except dynamic compiler)
• 256KB with JNI, reflection, verification,.

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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

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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

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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
• CVMnativesporting_layer
• Static ROM RAM req. 410 KB

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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

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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 (CVMnativesportinglibraries)
• Static ROM RAM req. 1421 KB
• Java libraries natives for Foundation Profile
• Static ROM RAM req 553 KB
• Foundation TOTAL (CVMnativesportinglibraries)
• Static ROM RAM req. 1974 KB