Java Reference
In-Depth Information
•
The Foundation Profile JSR000046
•
The Personal Profile JSR000062
•
The Personal Basis Profile JSR000129
•
The RMI Profile JSR000066
Note
Because this topic is intended to cover CLDC-based profiles, it gives only a short
overview about the JSRs that are available for CDC and focuses on covering CLDC-
based applications only.
A comparison between CDC and CLDC appears in the next section.
J2ME Configurations and Profiles
Obviously, the standard Java libraries are just too big for the Java 2 Micro Edition. Once the KVM
was available, the next logical step was to define appropriate libraries. But just downsizing the
standard libraries was not sufficient: The target devices have many special requirements that also
must be covered by libraries.
For example, many PDAs and all cellular phones do not have a file system. Instead, data is stored
persistently in simple databases in buffered RAM or flash memory. Obviously, a KVM library
would need to provide access to this kind of storage. Moreover, the specific needs diverge for the
potential KVM devices. A set top box (a device that decodes interactive TV signals) does not have
much in common with a cellular phone except that they both normally provide a small amount of
CPU power.
For these reasons, Sun decided to design several KVM profiles, one for each group of target
devices. Examples of KVM profiles are the Mobile Information Device Profile (MIDP) for
cellular phones and the PDA Profile for PDAs.
Like other official Java libraries, the profiles are designed in the Java Community Process. A
novelty in version 2.0 of the JCP is that not just companies but also individuals can participate.
For example, the authors of this topic are participating in the PDAP specification process as
invited experts.
The profiles are designed on top of KVM
configurations.
Whereas the profiles mainly address
device-type-specific issues, the configurations summarize the available basic KVM functionality
for devices with similar computing power and equipment characteristics. The following sections
describe KVM configurations and profiles in more detail.
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