Thursday, December 13, 2012

Fixed Checked Exceptions - The Xtend Way

Recently I stumbled across a post about checked exceptions in Sam Beran's Java 8 blog. What he basically described is a means to reduce the burden when dealing with legacy APIs that abused used Java's checked exceptions. His example is build around the construction of a which may throw an URISyntaxException.
Actually the URI class is not too bad, since it already provides a static factory URI#create(String) that wraps the checked URISyntaxException in an IllegalArgumentException, but you get the idea.

An Attempt to Tackle Checked Exception

Now, that Java will finally get lambda expressions with JSR 335, Sam suggests to use some utility class in order to avoid littering your code with try { .. } catch () statements. For example, Throwables#propagate could take care of that boilerplate:
Does that blend? I don't think so. That's still way too much code in order to deal with something that I cannot handle at all in the current context - and compared to the Java7 version, it's not much of an improvement either. The latter does not even carry the stacktrace so the actual code would more look like this:
According to the number of characters and taking into account that this snippet does not even tell the reader which sort of exception was expected, I would always go for the classic try { .. } catch ().

Or I'd Use Xtend.

Xtend will transparently throw the checked exception if you don't care about it. However, if you want to catch and handle it, feel free to do so. For the common other cases, the Xtend compiler uses the sneaky throw mechanism that is used in project Lombok, too. It just uses some generics magic to trick the Java compiler thus allowing to throw a checked exception without declaring it. You are free to catch that one whenever you want. There is no need to wrap it into some sort of RuntimeException just to convince the compiler that you know what you are doing.

By the way: You could of course use something like Throwables with Xtend, too:
That's what I consider fixing checked exceptions.