Java Platform, Micro Edition

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Java Platform, Micro Edition, or Java ME, is a Java platform designed for mobile devices and embedded systems. Target devices range from industrial controls to mobile phones and set-top boxes. Java ME was formerly known as Java 2 Platform, Micro Edition (J2ME).

Java ME was designed by Sun Microsystems, now a subsidiary of Oracle Corporation; the platform replaced a similar technology, PersonalJava. Originally developed under the Java Community Process as JSR 68, the different flavors of Java ME have evolved in separate JSRs. Sun provides a reference implementation of the specification, but has tended not to provide free binary implementations of its Java ME runtime environment for mobile devices, rather relying on third parties to provide their own.

As of 22 December 2006, the Java ME source code is licensed under the GNU General Public License, and is released under the project name phoneME.

As of 2008, all Java ME platforms are currently restricted to JRE 1.3 features and uses that version of the class file format (internally known as version 47.0). Should Sun ever declare a new round of Java ME configuration versions that support the later class file formats and language features, such as those corresponding JRE 1.5 or 1.6 (notably, generics), it will entail extra work on the part of all platform vendors to update their JREs.

Java ME devices implement a profile. The most common of these are the Mobile Information Device Profile aimed at mobile devices, such as cell phones, and the Personal Profile aimed at consumer products and embedded devices like set-top boxes and PDAs. Profiles are subsets of configurations, of which there are currently two: the Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC).^[1]

There are more than 2 billion Java ME enabled mobile phones and PDAs^[2].

[edit] Connected Limited Device Configuration

The Connected Limited Device Configuration (CLDC) contains a strict subset of the Java-class libraries, and is the minimum amount needed for a Java virtual machine to operate. CLDC is basically used to classify myriad devices into a fixed configuration.

A configuration provides the most basic set of libraries and virtual-machine features that must be present in each implementation of a J2ME environment. When coupled with one or more profiles, the Connected Limited Device Configuration gives developers a solid Java platform for creating applications for consumer and embedded devices.

[edit] Mobile Information Device Profile

Designed for mobile phones, the Mobile Information Device Profile includes a GUI, and a data storage API, and MIDP 2.0 includes a basic 2D gaming API. Applications written for this profile are called MIDlets. Almost all new cell phones come with a MIDP implementation, and it is now the de facto standard for downloadable cell phone games. However, many cellphones can run only those MIDlets that have been approved by the carrier, especially in North America^{[citation needed]}.

JSR 271: Mobile Information Device Profile 3 (Final release on 09 Dec, 2009) specified the 3rd generation Mobile Information Device Profile (MIDP3), expanding upon the functionality in all areas as well as improving interoperability across devices. A key design goal of MIDP3 is backward compatibility with MIDP2 content.

[edit] Information Module Profile

The Information Module Profile (IMP) is a profile for embedded, "headless" devices such as vending machines, industrial embedded applications, security systems, and similar devices with either simple or no display and with some limited network connectivity.

Originally introduced by Siemens Mobile and Nokia as JSR-195, IMP 1.0 is a strict subset of MIDP 1.0 except that it doesn't include user interface APIs — in other words, it doesn't include support for the Java package javax.microedition.lcdui. JSR-228, also known as IMP-NG, is IMP's next generation that is based on MIDP 2.0, leveraging MIDP 2.0's new security and networking types and APIs, and other APIs such as PushRegistry and platformRequest(), but again it doesn't include UI APIs, nor the game API.

[edit] Connected Device Configuration

The Connected Device Configuration is a subset of Java SE, containing almost all the libraries that are not GUI related. It is richer than CLDC.

[edit] Foundation Profile

The Foundation Profile is a Java ME Connected Device Configuration (CDC) profile. This profile is intended to be used by devices requiring a complete implementation of the Java virtual machine up to and including the entire Java Platform, Standard Edition API. Typical implementations will use some subset of that API set depending on the additional profiles supported. This document describes the facilities that the Foundation Profile provides to the device and other profiles that use it. This specification was developed under the Java Community Process.

[edit] Personal Basis Profile

The Personal Basis Profile extends the Foundation Profile to include lightweight GUI support in the form of an AWT subset. This is the platform that BD-J is built upon.

[edit] Personal Profile

The Personal Profile is an extension of the Personal Basis Profile, and includes a more comprehensive AWT subset and adds applet support.

[edit] Implementations

Sun provides a reference implementation of these configurations and profiles for MIDP and CDC. Starting with the JavaME 3.0 SDK, a Netbeans-based IDE will support them in a single IDE.

In contrast to the numerous binary implementations of the Java Platform Sun provides on server and workstation machines, Sun does not provide any binaries for the platforms of Java ME targets with the exception of an MIDP 1.0 JRE (JVM) for Palm OS.^[3] Sun provides no J2ME JRE for the Microsoft Windows Mobile (Pocket PC) based devices, despite an open-letter campaign to Sun to release a rumoured internal implementation of PersonalJava known by the code name "Captain America".^[4]

Operating systems targeting Java ME have been implemented by DoCoMo in the form of DoJa, and by SavaJe as SavaJe OS. The latter company was purchased by Sun in April 2007 and now forms the basis of Sun's JavaFX Mobile. The company IS2T provides Java ME virtual machine (MicroJvm), qualified as baremetal, where the virtual machine is the OS/RTOS: the device boots in Java.^[5]

MicroEmulator provides an open source (LGPL) implementation of CLDC and MIDP profiles.

The open-source Mika VM aims to implement JavaME CDC/FP, but is not certified as such (certified implementations are required to charge royalties, which is impractical for an open-source project). Consequently devices which use this implementation are not allowed to claim JavaME CDC compatibilty.

[edit] Getting Started

Java ME SDK (3.0), available on early release at project download page
NetBeans Mobility Pack, available at project home page
Eclipse Mobile Tools for Java, available at project home page

[edit] JSRs

[edit] Foundation

JSR #	Name	Description
68	J2ME Platform Specification
30	CLDC 1.x
37	MIDP 1.0
118	MIDP 2.x
139	CLDC 1.1
271	MIDP 3.0

[edit] Future

JSR #	Name	Description
297	Mobile 3D Graphics API (M3G) 2.0

[edit] Main Extensions

JSR #	Name	Description
75	File Connection and PIM	File system, contacts, calendar, to-do
82	Bluetooth
120	Wireless Messaging API (WMA)
135	Mobile Media API (MMAPI)	Audio, video, multimedia
172	Web Services
177	Security and Trust Services
179	Location API
180	SIP API
184	Mobile 3D Graphics	High level 3D graphics
185	Java Technology for the Wireless Industry (JTWI)	General
205	Wireless Messaging 2.0 (WMA)
211	Content Handler API
226	SVG 1.0
229	Payment API
234	Advanced Multimedia Supplements (AMMS)	MMAPI extensions
238	Mobile Internationalization API
239	Java Bindings for the OpenGL ES API
248	Mobile Service Architecture	General
256	Mobile Sensor API
287	SVG 2.0

[edit] See also

Java portal

[edit] Notes

^ Java ME Technology
^ [www.java.com/en/about/]
^ MIDP for Palm OS 1.0: Developing Java Applications for Palm OS Devices January 2002
^ CDC and Personal Profile - Open letter to SUN to produce a Personal Java JRE for Pocket PC 2003
^ IS2T

JSR 232: Mobile Operational Management An advanced OSGi technology based platform for mobile computing
JSR 291: Dynamic Component Support for Java SE - Symmetric programming model for Java SE to Java ME JSR 232

[edit] Bibliography

Hayun, Roy Ben (March 30, 2009). Java ME on Symbian OS: Inside the Smartphone Model (1st ed.). Wiley. pp. 482. ISBN 0470743182. http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470743182.html.
Knudsen, Jonathan (January 8, 2008). Kicking Butt with MIDP and MSA: Creating Great Mobile Applications (1st ed.). Prentice Hall. pp. 432. ISBN 0321463420. http://www.informit.com/store/product.aspx?isbn=9780321463425.
Li, Sing; Knudsen, Jonathan (April 25, 2005). Beginning J2ME: From Novice to Professional (3rd ed.). Apress. pp. 480. ISBN 1590594797. http://www.apress.com/book/view/9781590594797.

[edit] External links

Wikibooks has a book on the topic of

J2ME_Programming

[0] Java ME Technology

[1] [www.java.com/en/about/]

[2] MIDP for Palm OS 1.0: Developing Java Applications for Palm OS Devices January 2002

[3] CDC and Personal Profile - Open letter to SUN to produce a Personal Java JRE for Pocket PC 2003

[4] IS2T

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