Java Reference
In-Depth Information
interface DBManager conveys requests from the package Market to package
MarketDB .
The complete class diagram is shown in Figure 14.11. The classes belong-
ing to different packages are separated by a dashed line. All the packages
contain a limited set of classes. The best package is MarketDB : it contains the
BManager interface, the VolatileDB interface that implements an in-memory
database, and four data classes: Item , Employee , Customer and Transaction
The data classes do not perform any operations; they only contain the infor-
mation relative to an entity stored in the database.
Each operation of the employee on the graphical user interface triggers a
sequence of interactions that span all four packages. As an example we can
examine in detail the scenario related to the Connect use case, which is
shown in Figure 14.12.
When the employee at the counter pushes the “Connect” button (after
filling in the code and password fields) the graphical user interface invokes
the btConnect_actionPerformed method. This method takes the values of
code and password and calls the LocalProxy , through the MarketProxy inter-
face. The local proxy asks the server for authentication (through the Market
interface) which takes place in two stages: first the employee information is
CounterUI
CounterUI
Counter
1
0 proxy
1
LocalProxy
MarketProxy
*
0 market
1
BasicServer
Market
1
MarketDB
0 dbm
1
VolatileDB
DBManager
Item
Employee
Customer
Transaction
Figure 14.11 Complete class diagram
 
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