Instead of using IF statements everywhere to check and then throw business exceptions, I now modify my Exceptions and call "Exception.when(...)".
So this...
User user = userService.getUser(userId);
if(!user.isLoggedIn()){
throw new MyBusinessException("User is not logged in");
}
becomes...
User user = userService.getUser(userId); MyBusinessException.when(!user.isLoggedIn(),"User is not logged in");
It really is a lot easier to read the code when written like this.
The changes to your Exception class are easy too. All we are doing is hiding the conditional inside a static function. Just add a method like this...
static void when(boolean condition,String msg){
if(condition){
throw new BusinessException(msg);
}
}
I am mostly using this with a RESTful system based on JAX-RS, and I have to do a lot of condition checking,which was becoming a nightmare to read with all those IF statements. Now, it reads like a dream, well, rather like proper English, so a perfect DSL.
FYI: I did look into everything I could think of to make it easier to implement, ie: generics, inheritance, etc. But you cannot use static methods in either interfaces or abstracts, and exceptions are blocked from generics. So we are stuck implementing this method in every Exception Class, but I think it is worth it.
