CODEWITHSUNDEEP
javaexceptionclojure
Edward
Edward

Reputation: 4631

How to use an own Java-Exception-class within Clojure?

I wrote an own Exception (named MyOwnException) class in Java:

package com.stackoverflow.clojure;

import java.lang.RuntimeException;

public class MyOwnException extends RuntimeException {

    private static final long serialVersionUID = 3020795659981708312L;

    public MyOwnException(String s) {
        super("My own exception says: " + s);
    }

}

Now I'd like to use MyOwnException within my Clojure code. I tried several things, But I always got Class not found exceptions (.java and .clj are in the same package com.stackoverflow.clojure):

(ns com.stackoverflow.clojure.testForOwnExceptions)

;(import '[com.stackoverflow.clojure MyOwnException])

(defn casetest [x]
  (case x
    "a" "An a."
    "b" "A b."
;    (-> (clojure.core/format "Expression '%s' not defined." x)(MyOwnException.)(throw))
;    (-> (clojure.core/format "Expression '%s' not defined." x)(com.stackoverflow.clojure.MyOwnException.)(throw))
    (-> (clojure.core/format "Expression '%s' not defined." x)(IllegalArgumentException.)(throw))
    ))

;(prn(casetest "error"))

Besides that: how would a solution purely in Clojure look like? (definition of Exception class + usage)

Update (project.clj):

(defproject com.stackoverflow.clojure/tests "0.1.0-SNAPSHOT"
  :description "Tests of Clojure test-framework."
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.6.0"]
                 [instaparse "1.3.4"]]
  :source-paths      ["src/main/clojure"]
  :java-source-paths ["src/main/java"]
  :test-paths        ["src/test/clojure"]
  :java-test-paths   ["src/test/java"]
  )

Upvotes: 2

Views: 544

Answers (2)

R_User
R_User

Reputation: 11082

Using

(import '[com.stackoverflow.clojure MyOwnException])

should work together with

...
(-> (clojure.core/format "Expression '%s' not defined." x)(MyOwnException.)(throw))
...

Or the full qualified name alone:

...
(-> (clojure.core/format "Expression '%s' not defined." x)(com.stackoverflow.clojure.MyOwnException.)(throw))
...

Since you already had the correct code within your question (outcommented parts), I guess that something went wrong with your REPL. Maybe you should restart it before running one of the following code-combinations. And keep in mind: only running (prn(casetest "error")) does not automatically change the code of the function. You have to send the complete new code to the REPL (e.g. by using Run as/Clojure Application)

(ns com.stackoverflow.clojure.testForOwnExceptions)

(import '[com.stackoverflow.clojure MyOwnException])

(defn casetest [x]
  (case x
    "a" "An a."
    "b" "A b."
    (-> (clojure.core/format "Expression '%s' not defined." x)(MyOwnException.)(throw))
    ))

(prn(casetest "error"))

or

(ns com.stackoverflow.clojure.testForOwnExceptions)

(defn casetest [x]
  (case x
    "a" "An a."
    "b" "A b."
    (-> (clojure.core/format "Expression '%s' not defined." x)(MyOwnException.)(throw))
    ))

(prn(casetest "error"))

Upvotes: 1

Chiron
Chiron

Reputation: 20245

How you are running your code? Are you compiling your Java source code first? And after compilation, are Java class files are in class path?

I would suggest to use Leiningen and to use different structure for your source. Don't mix sources in one package. Have for an example src/main/java and src/main/clojure'.

Have a look at: Polyglot (Clojure, Java) Projects With Leiningen.

Upvotes: 2

Related Questions