My basic rule is : Unless you can fix the problem which caused the exception, do not catch it, let it bubble up to a level where it can be dealt with. In my experience, 95% of all catch blocks either just ignore the exception (catch {}) or merely log the error and rethrow the … Read more
You can only specify one type per on xxx catch(e) { line or alternatively use catch(e) to catch all (remaining – see below) exception types. The type after on is used as type for the parameter to catch(e). Having a set of types for this parameter wouldn’t work out well. try { … } on … Read more
In Haskell, I’d be wrapping this code in some combination of monads, using Maybe’s and Either’s and translating and propagating errors as necessary. In the end, it all gets to an IO monad where I am able to output the status to the user. In another language, I simply throw an exception and catch in … Read more
Looking in my own code, I found a place in my logging code where, after failing to write to a file and failing to write to the event log, it swallows the error as there is no place left to report it. That’s one example: there aren’t many others.
http.createClient has been deprecated. Here is a quick example of how to handle errors using the new http.request: var http = require(“http”); var options = { host : “www.example.com” }; var request = http.request(options, function(req) { … }); request.on(‘error’, function(err) { // Handle error }); request.end();
This behavior is specified in the class documentation of CompletionStage (fourth bullet): Method handle additionally allows the stage to compute a replacement result that may enable further processing by other dependent stages. In all other cases, if a stage’s computation terminates abruptly with an (unchecked) exception or error, then all dependent stages requiring its completion … Read more
Reading these answers, I find it very unhelpful to say, “Exceptions should only be used for exceptional conditions”. This begs the whole question of what is an “exceptional condition”. This is a subjective term, the best definition of which is “any condition that your normal logic flow doesn’t deal with”. In other words, an exceptional … Read more
You need to wrap your string in a Throwable: (throw (Throwable. “Some text”)) or (throw (Exception. “Some text”)) You can set up a try/catch/finally block as well: (defn myDivision [x y] (try (/ x y) (catch ArithmeticException e (println “Exception message: ” (.getMessage e))) (finally (println “Done.”)))) REPL session: user=> (myDivision 4 2) Done. 2 … Read more
Panic/Recover are function scoped. It’s like saying that you’re only allowed one try/catch block in each function and the try has to cover the whole function. This makes it really annoying to use Panic/Recover in the same way that java/python/c# etc. use exceptions. This is intentional. This also encourages people to use Panic/Recover in the … Read more
Rather than generating custom classes, there are two much simpler ways to use custom exceptions: Use slingshot – this provides custom throw+ and catch+ macros that let you throw and catch any object, as well as exceptions. In clojure 1.4 and above, you can use clojure.core/ex-info and clojure.core/ex-data to generate and catch a clojure.lang.ExceptionInfo class, … Read more