The bank fasl file defines three abstract servant classes BankingDemo:account-servant
, BankingDemo:checkingAccount-servant
, and BankingDemo:bank-servant
corresponding to the IDL interfaces account
, checkingAccount
, and bank
. The class BankingDemo:checkingAccount-servant
is defined to inherit from BankingDemo:account-servant
, matching the inheritance relationship in the IDL.
Note that each class inherits from the abstract class PortableServer:ServantBase
, allowing instances of the class to be registered with a POA.
In our implementation of the bank server, these servant classes are implemented by the subclasses
The bank-implementation
class implements BankingDemo:bank-servant
by representing a bank as a connection to a database:
(defclass bank-implementation (BankingDemo:Bank-servant)
((connection :initarg :connection)
(poa :initarg :poa)
(account-impls :initform nil)))
We have included the poa
slot to record the POA in which the bank servant is active, so that servants representing accounts at the bank can be registered in the same POA. A slot op:name
corresponding to the attribute name defined in the IDL is inherited from the Bank-servant
, as are definitions of accessor functions for this slot.
The account-implementation
class implements BankingDemo:account-servant
:
(defclass account-implementation (BankingDemo:Account-servant)
((bank :initarg :bank)))
An instance of this class represents an account. The bank
slot provides a connection to the database that holds the account's record. Slots op:name
and op:balance
, corresponding to attributes defined in the IDL, are inherited from account-servant
. The name
slot identifies the record in the database.
Finally, the checkingAccount-implementation
class implements BankingDemo:checkingAccount-servant
simply by inheriting from account-implementation
:
(defclass checkingaccount-implementation (Bankingdemo:Checkingaccount-servant account-implementation)
())
A slot op:limit
, corresponding to the attribute limit defined in the IDL, is inherited from checkingaccount-servant
.