Java Micro Edition

JavaMicroEdition is an edition of the Java platform that is tailored toward the needs of non-desktop computing, such as on consumer, mobile, and embedded devices. See http://java.sun.com/j2me/.

JavaMicroEdition (or Java ME) is simply a rebranding of the Java 2 Platform, Micro Edition (J2ME). This rebranding was announced at the JavaOne conference in 2005. This will take some time; many materials still refer to J2ME.

In order to accommodate the broad range of application areas, the technology has been classified according to three concepts:

• a configuration, which is a VM specification plus a set of class library APIs;
• a profile, a set of class library APIs that define a complete application environment; and
• optional packages, which are optional class library APIs to support specific features which might appear on a device.

These concepts in turn have been assembled into three main "stacks" of APIs:

• CDC/Foundation/Personal
• CLDC/MIDP
• JavaCard

More information about these stacks can be found on the page http://java.sun.com/j2me/.

Currently (November 2005) a great deal of activity is currently occurring in the "mobile services architecture" (MSA) JSRs, JSR-248 and JSR-249. These JSRs group together configurations, profiles, and optional package specifications, and clarify the specifications, with the intent of creating a unified application environment for mobile handsets. JSR-248 applies to the CLDC stack, and JSR-249 applies to the CDC stack. See http://www.jcp.org/en/jsr/detail?id=248 and http://www.jcp.org/en/jsr/detail?id=249 for more information about these efforts.

The PDA Profile was turned into the PDA Optional Packages. It delivered two API libraries: one for filesystem access and the other for PIM (address-book, calendar, and to-do) database access. The RMI Profile was turned into the RMI Optional Package.

-- StuartMarks

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WhatHappened? Is the following information still useful for developers in late 2005?

Are there good support for JavaMicroEdition by EclipseIde, in a manner that is vendor neutral? Can JavaMicroEdition compliant software consume services provided by MicrosoftDotNet? What references exist?

• Enrique Ortiz (member of MIDP 2 expert group) has an Aug04 blog that provided a critique of JavaMicroEdition at http://www.j2medeveloper.com/blog/cldc-based-profiles/comments-on-cldc-profiles-today.html. In Nov05 he appeared at C2 to reaffirm his viewpoint, and observed " the observations are still valid - but the ideal organization that I proposed on my writeup is too utopian, and will never happen. And it won't happen because investments on current architecture won't allow it, and from the application and end-user perspective how things are organized really doesn't matter, as long as the functionality is still there. My proposed organization do matter though to Java ME runtime implementors, interested on leveraging functionality across (and reducing cost) from the botton up -- ceo "
  • Is the above information better suited for the ConnectedLimitedDeviceConfiguration page? I do not know JavaPlatform but am looking for better tools to develop for the HandheldComputers runing WindowsMobile and connecting to DotNet server components. If you are still around and have information on whether JavaMicroEdition (or for that matter another non DotNet clientside tool) may offer better developer toolset for that need please share your insights here or JavaAndDotNet. Thanks from David -- dl

Moved from JavaTwoMicroEdition

J2ME is not actually one software platform, but several: basically all Sun Java platforms smaller than JavaTwoStandardEdition? (the version we use on desktop machines and in e.g. NetscapeNavigator).

Pre-existing platforms that fit within J2ME include:

• JavaCard
• PersonalJava (being replaced by / becoming J2ME ConnectedDeviceConfiguration? ?)

But the new approach is to structure J2ME as 'Configurations' (JVM + fundamental API set) upon which are layered 'Profiles' (extended API sets suiting a particular class of device).

There are currently two Configurations, with associated Profiles:

• ConnectedLimitedDeviceConfiguration ('CLDC', implemented by K Virtual Machine, see JavaOnThePalm)
  • MobileInformationDeviceProfile ('MIDP', for mobile phones, two-way pagers, etc...)
  • PdaProfile? ('PDAP', for devices like Palm with larger screens than phones)
• ConnectedDeviceConfiguration? ('CDC', for 'Communicators' etc.)
  • FoundationProfile? (underlying connection capabilities, no UI required)
  • PersonalBasisProfile? (basic UI capabilities)
  • PersonalProfile? (I think this on top of CDC = former PersonalJava)
  • RmiProfile? (adding RMI capabilities to CDC)

Further clarification (and fixes) appreciated!

Contributors for JavaTwoMicroEdition: DavidPrice

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Resources

For some reason a lot of ApplicationDevelopment links I have found are done around 2002, and nothing for 2004 and 2005.

• Design patterns (Cascading Menu, Wizard Dialog, Pagination, and Slide Show) at http://www.javaworld.com/javaworld/jw-12-2002/jw-1213-j2medesign_p.html

• Comparison between JavaMicroEdition and DotNetCompactFramework philosophies, approaches and features at http://www.javaworld.com/javaworld/jw-02-2003/jw-0221-wireless_p.html. A followup article illustrates an example of Java client link to MS MapPoint? DotNet server at http://enterprisej2me.com/pages/yuan/articles/jw-0516-wireless.html

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Trying to run the sun J2ME converter for palm to create .prc files from the jar file it says the .jad and .jar don't match. It seems you are expected to run the build.bat to make the .jar from .jad (this is on windows) which is separate from the "build" button on the KToolbar (which only makes a .jad file). If you look in for example c:\wtk22\apps\demos\bin you'll see what I mean. Then you are expected to manually edit the .jad file to put what the file size of the .jar is before the converter will work. Why couldn't the "build" button on the KToolbar just do the whole process? These are the latest versions just downloaded. I made a little program read the file size and update the .jad, but surely that is not the SimplestThingThatCouldPossiblyWork ? Is there some other setting I am missing?

Try the Project > Package > Create Package menu option. It's a little odd that the "build" button compiles the classes and updates the .jad but leaves the old .jar in place. Using the "Create Package" command should create a fresh .jar and update the .jad to match. -- StuartMarks

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