Learning Exception Handling Patterns [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.

---

Want to improve this question? Update the question so it focuses on one problem only by editing this post.

Closed 6 years ago.

Improve this question

One thing that has alw开发者_运维技巧ays mystified me in programming is the use of appropriate exception handling. Code Complete points out that often times 90% of code is focused on handling exceptions. While I know the basics of implementing a basic exception, I have not found good general resources for such an important topic.

I am looking for good resources (not necessarily tied to a specific language) for learning how to implement good Exception Handling techniques. Most of the Exception Handling topics on stackoverflow seem to focus on a specific situation in a specific language. What would be your recommendations?

---

I have been a designer and coder of safety-critical systems for many years, and key to that type of system is robustness, one aspect of which is exception handling.

Some basic best practices:

1) At any level, catch only those exceptions you can deal with then and there. To "deal with" almost always means to retry or give up what you were trying to do, and that usually means that you should catch the exception one level up from where the exception-throwing call is issued.

2) Catch exactly those exceptions listed by the API documentation, no more, no less. Even if there are five exceptions listed for a call, don't catch their common base class (if they have one). However, you don't always need to catch all exceptions from the same call in the same place.

3) Don't pass nitty-gritty exceptions up to a level where they carry no meaningful information. Instead, catch the exception at the low level, log it if appropriate and return a status code or throw a more generic exception to the caller above.

4) Only use (and do use) catch-all handlers when you are in a critical section. Catch the exception, relinquish the resource (semaphore or whatever), rethrow the exception.

5) Logging an exception is not handling it. If all you do in a particular handler is log the exception, you should probably get rid of that handler.

6) Be very careful with exception handlers in loops, especially loops without a delay or a way out if the exception is thrown. You can easily get stuck in a busy loop that way.

---

I know of two good resources for proper exception handling strategies, they however pertain more to the .NET framework..

The first is the framework design guidelines by Krzysztof Cwalina (The lead designer of the .NET framework)

http://blogs.msdn.com/b/kcwalina/archive/2005/03/16/396787.aspx

The second is about what happens under the hood when exceptions are thrown, it will provide some good insight to help with your decision on how to handle exception. The book is called C# via CLR by Jeffrey Richter

http://shop.oreilly.com/product/9780735627048.do

Hope this helps.