Introduction to CORBA IDL -- Raising Exceptions in IDL Operations

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Raising Exceptions in IDL Operations

IDL operations can raise exceptions to indicate the occurrence of an error.

CORBA defines two types of exceptions:
- System exceptions are a set of standard exceptions defined by CORBA.
- Userdefined exceptions are exceptions that you define in your IDL specification.
Implicitly, all IDL operations can raise any of the CORBA system exceptions.
No reference to system exceptions appears in an IDL specification.
To specify that an operation can raise a user-defined exception, first define the exception structure and then add an IDL raises clause to the operation definition.
For example, the operation makeWithdrawal in interface Account could raise an exception to indicate that the withdrawal has failed, as follows:
```
 

    module Finance { 
      interface Account { 
      exception WithdrawalFailure { 
        string reason; 
      }; 
      void makeWithdrawal(in float amount, 
                          out float newBalance) 
      raises(WithdrawalFailure); 
      ... 
      }; 
    }; 
```
An IDL exception is a data structure that contains member fields.
In the above example, the exception WithdrawalFailure includes a single member of type string.
The raises clause follows the definition of operation makeWithdrawal to indicate that this operation can raise exception WithdrawalFailure.
If an operation can raise more then one type of user-defined exception, then include each exception identifier in the raises clause and separate the identifiers using commas.