Next Generation Wireless Applications: Creating Mobile Applications in a Web 2.0 and Mobile 2.0 World, 2nd Edition

11.11 MIDP OTA DOWNLOAD MECHANISM

The mechanism for downloading a MIDlet to a device takes place using HTTP or WSP, as shown in Figure 11.29. The objective of the process is to download MIDlets, in the form of JAR files, from a central source, such as a database or file server, placing them into the JAR memory space in the device. As previously mentioned, a portion of device memory belongs to the JRE and it used for storing MIDlets. The file format is a compressed form of the compiled class file, using the ZIP file format.

The Java Application Management System (AMS) is responsible for the downloading and the process, which also includes installation of the MIDlet class file on the device. The AMS is mandatory for MIDP-compliant devices and gives the user the ability to download and run MIDlets. The Java application manager will provide a means for the user to run any MIDlet in the future.

Figure 11.29 shows us the server component responsible for managing MIDlets as a centralised resource, which might well be a J2EE platform. This ‘MIDlet manager’ or ‘vending machine’ could be a bespoke application, or an off-the-shelf service delivery platform (SDP) aimed at content management, including games ‘vending’ (assuming the MIDlets are games³⁵). There are many vending servers on the market. An example is the Integrated Mobile Marketplace from July Systems, Inc.

As Figure 11.30 shows, the first thing that the application manager does is to download a JAD file. The JAD describes the essential ...