Question

I have an error/exception that is thrown by a particular method. Any time this error occurs, I want to log it. Would it be good practice to log the error within the initial method, and then re-throw it? That way I would not need to log it in the catch statements of any function that calls this method.

It would look something like this:

public void doSomething() throws Exception{
    try{
        someFunction(); // throws Exception
    } catch (Exception e){
        logger.fatal(e.getMessage()); // always log this Excpetion
        throw e;            
    }
}

My concern was the re-throwing of exact same error. I have not seen this done, and I wondered if it would be considered bad practice.

EDIT: I should add that this Exception should never ever happen. That might help understand this situation.

Answer 1

It really depends on your logging preferences. For example you database access layer may have a method that takes a SQL query as a String as an argument and executes it in the DB. Now you may want to log any SQLException in that layer and then wrap the SQLException by a custom exception [like a DatabaseException] and then re-throw it back to the parent layer. You may also want to encapsulate some additional behaviour like a boolean shouldRetry in your DatabaseException object so that the parent layer may retry the operation again. Logging the SQLException right away will let you debug the issue more easily later.

EDIT:

This approach makes more sense when your parent layer does an operation that might throw more than one kind of exception. For example, in the above scenario, the method that takes the SQL query might also throw a InvalidHostException if the database manager is unreachable or a ConnectionRefusedException, if the database manager refused connection due to overload. In such a case you might log the exception and then wrap it with the more general DatabaseException. Also if the method threw a ConnectionRefusedException then you might want to set the shouldRetry variable to true; while the same will be false for a InvalidHostException. This allows the caller API to try to call the method again after sometime if the value of shouldRetry was set to true.

NOTE: Except SQLException, the rest are creations of my imagination. 🙂