Java Reference
In-Depth Information
Implement other internet mail protocols. Currently POP3 is the only
protocol that can be used to access mail servers. It is important to be able
to use the IMAP protocol as well.
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16.8
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Assessment
Architectural model
. The ubiquitous email system facilitates the access to
the mail server. It is an example of broker-based architecture, where the
UbiMail application plays the role of broker. It adapts the POP3 protocol,
which is mail-specific and computer-oriented, to the HTML
HTTP protocol,
which is general purpose and human-oriented.
Paradigm
. The communication between the system and both the mail
server and the clients is based on well-defined protocols. It is an example of
declarative communication.
Technology
. The interaction with the client through HTML
HTTP is
implemented by means of the JSP technology. The interaction with the mail
server through POP3 is based on the classes in the Java standard extension
library.
Architecture
Multiple presentations
Context
Distributed computing.
Multiple access devices.
Problem
We need access to the same information through different
media and devices. As the user changes device he
she
must be offered the same service according to the device's
capabilities.
Forces or tradeoffs
The same service must be presented through different
channels.
Each device has different capabilities.
The detail that can be presented depends heavily on the
device capability.
Solution
Add a presentation layer for each specific device and let it
select the features that can be shown on the device and
organize the contents in the most suitable way. All the
versions of the user interface are based on the same
back-end component; they only adapt the information in
the back end to specific languages
devices. In addition we
need an entry point that can redirect the user to the most
suitable presentation on the basis of the user's device
capabilities.
Examples
As an example, using JSP to provide access to devices
using different languages would yield the following
structure:
