Introduction to the Java 2 Micro Edition (J2ME) Platform
Device Application Management Systems
All J2ME applications—MIDlets and others—are real Java applications that run under the control of a Java VM. But what controls the Java VM, for instance on a mobile phone? There's no command shell from which you can invoke your favorite Java applications like you do on your workstation. Starting, stopping, and managing the execution of J2ME applications is controlled by application management software (AMS) that resides on the device. In fact, the AMS controls the entire application lifecycle, from installation, upgrade and version management, to removal of application software.
The device manufacturer typically provides the AMS software. This is the most logical scenario because AMS software must work in conjunction with the device's native system software, which, presumably, the manufacturer knows best. Nevertheless, third parties can also develop AMS systems for specific devices. AMS software could be written, for example, in Java or in some native language such as C.
The J2ME platform addresses two classes of pervasive computing devices. The first class consists of stationary devices with fixed network connections such as TV set-top boxes. The second consists of personal, mobile devices with intermittent network connectivity, such as PDAs, mobile phones, and so on.
Different combinations of J2ME configurations and profiles support these two classes of devices. The CDC configuration and Foundation Profile support the former class of devices, and the CLDC configuration and MIDP profile support the latter.
A configuration attempts to provide interfaces for system-level services. A profile attempts to provide standard interfaces for application-level services. The configuration enables the profile, providing the necessary medium and mechanisms.
Devices must have some AMS to "bootstrap" the process of provisioning J2ME applications on devices. The device manufacturer usually provides the AMS.
This is a sample chapter of Wireless J2ME Platform Programming
by Vartan Piroumian
For the full text, visit http://www.phptr.com
©2002 Pearson Education. All Rights Reserved.
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