Question

Which one will be better: ErrorCode or Exception for that situation?

I have ever been seeing these two error handling techniques. I don’t know the disadvantages and advantages for each technique.

public void doOperation(Data data) throws MyException {
    try {
        // do DB operation
    } catch (SQLException e) {
        /* It can be ChildRecordFoundException, ParentRecordNotFoundException
         * NullValueFoundException, DuplicateException, etc..
         */
        throw translateException(e);
    }
}

or

public void doOperation(Data data) throws MyException {
    try {
        // do DB operation
    } catch (SQLException e) {
        /* It can be "CHILD_RECORD_FOUND, "PARENT_RECORD_NOT_FOUND"
         * "NULL_VALUE_FOUND", "DUPLICATE_VALUE_FOUND", etc..
         */
        String errorCode = getErrorCode(e);
        MyException exc = new MyException();
        exc.setErrorCode(errorCode);
        throw exc;
    }
}

For second method, the error code retrieve form configuration file. We can add Error Code based on the SQL Vender Code.

SQL_ERROR_CODE.properties

#MySQL Database
1062=DUPLICATE_KEY_FOUND
1216=CHILD_RECORD_FOUND
1217=PARENT_RECORD_NOT_FOUND
1048=NULL_VALUE_FOUND
1205=RECORD_HAS_BEEN_LOCKED

Caller client for method 1

    try {

    } catch(MyException e) {
        if(e instanceof ChildRecordFoundException) {
            showMessage(...);
        } else if(e instanceof ParentRecordNotFoundException) {
            showMessage(...);
        } else if(e instanceof NullValueFoundException) {
            showMessage(...);
        } else if(e instanceof DuplicateException) {
            showMessage(...);
        }
    }

Caller client for method 2

    try {

    } catch(MyException e) {
        if(e.getErrorCode().equals("CHILD_RECORD_FOUND")) {
            showMessage(...);
        } else if(e.getErrorCode().equals("PARENT_RECORD_NOT_FOUND") {
            showMessage(...);
        } else if(e.getErrorCode().equals("NULL_VALUE_FOUND") {
            showMessage(...);
        } else if(e.getErrorCode().equals("DUPLICATE_VALUE_FOUND") {
            showMessage(...);
        }
    }

Answer 1

Strange question, since both approaches do the same thing: they transform a checked SqlException in a different exception which seems to be unchecked. So the first one is the better one because it moves this into a single method.

Both leave some questions to be asked:

• Isn’t there some infrastructure that can do this conversion (Spring Template was mentioned in another answer)

• Do you really want checked Exceptions, in my mind they are hardly ever worth the trouble.

• Who is doing the real handling of the exception, does it get all the information needed? I would normaly expect some additional information about the transaction that failed inside of MyException, like: What did we try to do? (e.g. update a busines object); On what kind of object? (e.g. a Person); How can we/the user Identify the object (e.g. person.id + person.lastname + person.firstname). You will need this kind of information if you want to produce log/error message that tell you or your user more than ‘Oops, something is wrong’

• Why is MyException mutable (at least in the 2nd example)