J2ME MIDlet is limited, why not Java applications on mobile?

Discussion in 'Java' started by chen_lin99, Apr 22, 2005.

  1. chen_lin99

    chen_lin99 Guest


    For a while I have been wandering about this, any comments or you point
    out if I am wrong, it would be appreciated:

    The J2ME platform (I am using Sun's J2ME Wireless Toolkit) looks
    providing a very limited range of functionality. For example, MIDlet
    cannot detect (or be triggered) when there is an incoming call on the
    mobile phone, nor can it receive a regular SMS message sent from
    another mobile phone (correct me if I am wrong).

    With these limitations (or restrictions) in effect, I think it's very
    hard to develop a powerful software on the J2ME platform, for example,
    a powerful phone call management software, which can block certain
    phone numbers from calling in, which can automatically redirect certain
    incoming calls to another pre-configured phone number.

    A war game on mobile phone, I believe J2ME is capable of; but more
    powerful things, especially those interacting with IO's, I don't think
    MIDlet is.

    I understand for security reason, MIDlet can only execute within

    However, I wander, why there cannot be Java applications as well, just
    like on the PC. If a user installs a Java application onto his mobile
    phone, via bluetooth or data cable or whatever, that means he trusts
    the application and he has the right to do it.

    In addition, digital certificate can be used to sign the Java
    application installation, and certain trusted digital certificates can
    be pre-set on the mobile phone. So even with OTA, a Java application
    (not only a MIDlet) can be downloaded and installed and started on the
    mobile phone, as long as the software passes the certificate checking.

    So, I would like to ask, why not Java applications on the mobile phone?
    On PC, there are applets and applications; why not on mobile phones,
    there are MIDlets and applications as well?

    Somewhere I read about "Personal Java", maybe that's the Java
    applications I meant here? But besides that, I did not hear much more
    about "Personal Java".

    Thank you,
    chen_lin99, Apr 22, 2005
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  2. That's because they're designed to run on devices with limited resources.
    It can receive and respond to SMS messages sent to specific ports on the
    handset, but it is not allowed to intercept and process SMS messages on
    ports for which the MIDlet's not registered. This was decided by the
    handset manufacturers themselves who were on the expert group defining
    the WMA.
    Darryl Pierce, Apr 22, 2005
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  3. chen_lin99

    chen_lin99 Guest


    I think it's true that J2ME runtime hardware environment is pertty
    resource limited. However, by looking at MIDlet design, like its
    start(), pause(), APIs and alike, its security permissions, and other
    technical details, I think fundamentally MIDlet was created with the
    sandbox restrictions in mind, just like Applet.

    Yes, it's true there is no problem for MIDlets to receive SMS messages
    on specific ports; in other words, MIDlets can communicate with MIDlets
    via specific and of course, pre-agreed port, but MIDlets can not
    receive SMS messages which are not from a MIDlet it "knows".

    I think, fundamentally, my question, i.e., why Java applications alike
    cannot exist on mobile phones, was not answered. Limited resources
    should not be the reason. Specific SMS message communication port is
    only a technical detail.

    Future comments are appreciated.

    chen_lin99, Apr 25, 2005
  4. Yes, it was. And it's stated very clearly in the specification and the
    white papers that that's the intention behind the MIDP.
    No, it can respond to any SMS message sent to the port on which it's
    listening. It doesn't matter if the SMS message was sent by another
    phone, a servlet, an email application, etc. All that matters is that
    it's sent to the specific port on which the MIDlet is registered as a
    Your question, as worded, makes no sense. What are you trying to find out?
    Darryl Pierce, Apr 25, 2005
  5. chen_lin99

    chen_lin99 Guest

    Here, I am not going to explain my topic any more. If interested in
    this topic, one may go to Nokia discussion board:


    where this topic got good feedbacks and discussions.

    chen_lin99, Apr 27, 2005
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