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All business logic as much as is practical should conform to the java command
design pattern. All code that results in a change to data must be implemented
as a command. A Command describes an
individual unit of work or transaction. Execution of a command is usually
a result of a business event, ie
A student enrolling in a subject.
Execute the command. An optional variable number of parameters should be passed at object instantiation.
before the Command.execute() method is called. Should it not be possible to
complete the execution of the command for any reason, the command must
When an IOException is thrown, the data store should not have been altered in anyway. (ie SQL transactions are