defexception

A simple Clojure library that allows one to dynamically define Java Exception classes in Clojure.

Motivation

Sometimes you just want a quick Exception class that you can catch directly. defexception uses Java bytecode to dynamically create a Java class that directly inherits from clojure.lang.ExceptionInfo.

The created exception class does not add any behavior to clojure.lang.ExceptionInfo.

Dependency

deps.edn dependency information:

com.rpl/defexception {:mvn/version "0.2.4"}

Leiningen dependency information:

[com.rpl/defexception "0.2.4"]

Usage

To create your own exception class you can do this:

(ns foo.bar
 (:require [com.rpl.defexception :refer [defexception]]))

(defexception MyException)

This will create the foo.bar.MyException class that inherits from clojure.lang.ExceptionInfo. This will also import the class into the current namespace and create a helper function foo.bar/->MyException to help you construct the exception class.

Now you can do this:

(try
  (throw (->MyException "My bad!" {:my-bad 1}))
  (catch MyException e
    (ex-data e)))
;; => {:my-bad 1}

The generated ->MyException helper function has several signatures to help you instantiate your exception.

;; creates an exception with no message or ex-data
(->MyException)

;; creates an exception with only ex-data
(->MyException {:hello 1})

;; creates an exception with only a message
(->MyException "My Bad!")

;; creates an exception with both a message and ex-data
(->MyException "My Bad!" {:hello 1})

;; creates an exception with a message, ex-data and a cause
(->MyException "My Bad!" {:hello 1} (Exception. "The cause"))

AOT compilation

Care was taken to make these exceptions compatible with Clojure's AOT compilation.

License

Copyright © 2019 - 2020 Red Planet Labs Inc.

Distributed under the Eclipse Public License version 1.0