Java Reference
In-Depth Information
Connected Device Configuration (CDC) . Essentially, this configuration is designed for
next-generation devices with more robust resources than CLDCs. Typically, these devices
run on a 32-bit CPU, and have at least 2MB of RAM totally available for the Java plat-
form and client applications.
One requirement among device manufacturers is the capability to dynamically change the fea-
tures provided by the device. That is, the software is not hard-coded within the device once and
for all, but could be to some extent dynamically loaded. Here, deployment techniques come
into play. We discussed in the previous chapter the design issues related with Java deployment
that still apply here.
The configurations don't address lifecycle issues (installation, launching, and removal), leaving
these and other features to their profiles. Consequently, we are obliged to discuss deployment
issues on a profile basis. This would be beyond the scope of this topic, so we will see in detail
the deployment of only one interesting profile, the Mobile Information Device Profile (MIDP).
Deploying MIDlets
The Mobile Information Device Profile (MIDP) is a set of Java APIs that, together with the
Connected Limited Device Configuration (CLDC), provides a complete J2ME application
environment. It defines issues such as user interface, the application model, networking, and
persistence storage for mobile devices such as cellular phones and two-way pagers.
The code proposed here was developed and executed on the J2ME Wireless Toolkit from Sun,
available at http://www.javasoft.com/products/j2mewtoolkit/ .
Application Descriptor Files
An application descriptor file is a text file, encoded with Unicode, with the suffix .JAD . It is
made up of text lines composed as follows:
[attribute-name]+': '+[value]
Such attributes can be read by MIDlets using the static method MIDlet.getAppProperty .
Listing 5.1 shows an example of a JAD file.
L ISTING 5.1 An Example Of a Java Application Descriptor (JAD) File
MIDlet-Name: MIDletApplication
MIDlet-Version: 0.0.1
MIDlet-Vendor: myself
MIDlet-Jar-URL: http://www.myself.org/apps/app.jar
MIDlet-Jar-Size: 1234
MIDlet-Data-Size: 256
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