MIDP applications are called MIDlets. Even though the figure below defines MIDlets as applications built using the MIDP and CLDC only, one usually refer to OEM-specific applications as MIDlets also. MIDlets are usually distributed in MIDlet suites, available on the Internet through WAP.
| MIDP Applications | OEM-Specific Applications |
Native Applications |
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| OEM-Specific Classes |
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| MIDP | |||||
| CLDC | |||||
| Native System Software | |||||
| MID | |||||
OEM-specific applications rely on OEM-specific classes. Both Nokia and Sony Ericsson have their own classes for user interface and device specific functionality. E.g. vibration is provided through these specific classes. One of the main advantages of MIDlets is their portability. If you use OEM-specific classes you sacrifice this portability. Using Nokia classes will for certain give you an error if you run your MIDlet on a Sony Ericsson device.
MIDlets are usually available through MIDlet suites. A MIDlet suite consists of two files, a .jar and a .jad file. The Java ARchive (JAR) file contains your
compiled classes in a compressed and preverified fashion. All MIDlets must be preverified. This means that a checksum is computed, enabling the resource-constrained
MID to easily check the integrity of the jar-file (using only a few hundred bytes of memory). Several MIDlets may be included in a MIDlet suite. Hence, the JAR file
will contain all these MIDlet classes.
The Java Application Descriptor (JAD) file is a plain text file containing information about your MIDlet suite. All MIDlets must be named in this file, the size of the JAR
file must be included (and be correct!) and the URL to the JAR file must be present. In addition, the MIDlet suite version number is included here. This is essential
information for a MID. If the suite is already installed, it will know if a newer version is available. The size of the JAR file is important information, the MID can
determine if there is enough memory available to install the MIDlet suite. If all is well the MID can go to the supplied URL and download the JAR file. Other attributes
may be included as well. Midlet vendor and other information may be included on a nice-to-know basis. Check the MIDP specification for available attributes.
To deploy MIDlets on the Internet it should be no surprise that you need a web-server. Check out the WAP How-To for more information on this topic.
This page was last updated 14. Jul. 2006
Comments and feedback are highly appreciated.
You can reach me at: klings (at) nowires (dot) org