Developing The Bank Account IDL by Gopalan Suresh Raj

In Visual J++, the most simplest method to create an MTS server component is to first write your server code in pure Java and then create a COM wrapper for it. However, creating the component from scratch using the IDL will allow you more flexibility and control in coding the server component. Hence, we will develop our Bank Account from scratch using IDL.

1. Code the IDL
Write the code for the IDL as follows. Use guidgen.exe where necessary to generate new UUIDs. Code the Checking and Savings Account interfaces and create interfaces to access the Primary Key so that if we need to have a collection of keys that form our primary key, we can work easier.

Bank.idl

[
uuid (07D690F0-FB95-11d2-97E3-006097A7D34F),
version (1.0)
]
library Bank {

/*
   * Primary Key Interface for accounts
   */
importlib ("stdole32.tlb");
[
    uuid (07D690F1-FB95-11d2-97E3-006097A7D34F),
    dual
]
interface IAccountKey : IDispatch {
    HRESULT setKey ([in] int key);
}

/*
   * Checking creation interface
   */
[
    uuid (07D690F2-FB95-11d2-97E3-006097A7D34F),
    dual
]
interface ICheckingHome : IDispatch {
    HRESULT create ([in] IAccountKey* key,
                    [in] BSTR name,
                    [in] double startingBalance);
}

/*
   * Checking Interface for business rules
   */
[
    uuid(07D690F3-FB95-11d2-97E3-006097A7D34F),
    dual
]
interface IChecking : IDispatch {
    HRESULT credit ([in] double amount,
                    [in] IAccountKey* key);
    HRESULT debit ([in] double amount,
                   [in] IAccountKey* key);
    HRESULT getBalance ([in] IAccountKey* key,
                        [out, retval] double* balance);
    HRESULT getCustomerName ([in] IAccountKey* key,
                             [out, retval] BSTR* name);
}

/*
   * Checking Primary Key class
   */
[
    uuid(07D690F4-FB95-11d2-97E3-006097A7D34F)
]
coclass CheckingPK {
    interface IAccountKey;
};

/*
   * Checking class
   */
[
    uuid(07D690F5-FB95-11d2-97E3-006097A7D34F)
]
coclass Checking {
    interface ICheckingHome;
    interface IChecking;
};

/*
   * Savings creation interface
   */
[
    uuid (07D690F6-FB95-11d2-97E3-006097A7D34F),
    dual
]
interface ISavingsHome : IDispatch {
    HRESULT create ([in] IAccountKey* key,
                    [in] BSTR name,
                    [in] float interestRate,
                    [in] double startingBalance);
}

/*
   * Savings Interface for business rules
   */
[
    uuid(07D690F7-FB95-11d2-97E3-006097A7D34F),
    dual
]
interface ISavings : IDispatch {
    HRESULT credit ([in] double amount,
                    [in] IAccountKey* key);
    HRESULT debit ([in] double amount,
                   [in] IAccountKey* key);
    HRESULT getBalance ([in] IAccountKey* key,
                        [out, retval] double* balance);
    HRESULT getCustomerName ([in] IAccountKey* key,
                             [out, retval] BSTR* name);
    HRESULT getInterestRate ([in] IAccountKey* key,
                             [out, retval] float* rate);
}

/*
   * Savings Primary Key
   */
[
    uuid(07D690F8-FB95-11d2-97E3-006097A7D34F)
]
coclass SavingsPK {
    interface IAccountKey;
};

/*
   * Savings class
   */
[
    uuid(07D690F9-FB95-11d2-97E3-006097A7D34F)
]
coclass Savings {
    interface ISavingsHome;
    interface ISavings;
};
};

2. Generate the type library from the IDL
Use the midl.exe that comes with your VC++ to compile the IDL files. If the VC++ environment variables are not loaded use the full path to midl.exe. Notice that Bank.tlb will now appear.