This is very good advice Niclas thanks for it. I tend to agree with most of what you have here myself.
On Jan 3, 2008 10:49 PM, Niclas Hedhman <[EMAIL PROTECTED]> wrote: > On Friday 04 January 2008 06:15, Felix Knecht wrote: > > Client's reaction when exception happens | Exception type > > > -----------------------------------------+------------------------------- > > Client code cannot do anything | Make it an unchecked exception > > + > > Client code will take some useful | Make it a checked exception > > recovery action based on information in | > > exception > > On paper this sounds fine. But I kind of disagree. If a unchecked > exception > bubbles through the system to some high-up catcher which logs it, and then > acts, you often end up with a context-less information about the problem, > and > you need to dig into the stack trace. > > Instead, I typically recommend; > > Is this the result of a bug in the code? --> Unchecked. > Can this happen with no bugs in the code? --> Checked. > > Now, that is often a contract between the caller and callee. The callee > can > perhaps not know whether this could be the result from a bug or a 'normal > case'. *I* then use checked exception in the low-level method, and add a > wrapper at the caller end, which is used when the arguments (for instance) > are guaranteed to be Ok. For example; the constructor of URL throws > MalformedURLException, and when you do > > URL url = new URL( "http://www.apache.org"; ); > > it is really annoying that you need to catch it. So, you add your > newHttpUrl() > in a factory, which you call instead for the above kind of cases. > > By having checked exceptions for things that can happen in normal > situations > (disk full, no connection, wrong data input, et cetera) is to ensure that > each level in the call chain wraps a user relevant context and re-throw > the > exception, typically as a different type. So, the user is presented with a > caller chain like ; > "Build Error" -> > "Artifact org.apache.directory:core:1.1.0 missing" -> > "Can't download artifact org.apache.directory:core:1.1.0" -> > "No route to host: www.ibiblio.org" -> > "Connection error." > > without needing to dig into stacktraces, and often not know the context > enough > to have a clue what went wrong. > > IMHO, exception handling is a very sad chapter in most software. > > > Cheers > -- > Niclas Hedhman, Software Developer > > I live here; http://tinyurl.com/2qq9er > I work here; http://tinyurl.com/2ymelc > I relax here; http://tinyurl.com/2cgsug >
