Get stacktrace as string

Question

I'm using Clojure and I want to get my hands on a stack trace that I can log (ideally, i would like to get it as a String).

I see that (.getStackTrace e) returns a StackTraceElement[] but I don't know how to print something meaningful out of it. My second approach was (.printStackTrace e) with a PrintWriter as a parameter (because I know this is possible in Java), but I don't seem to get the correct syntax.

Thanks.

Pressing

Answer 1

if number23_cn's solution is a bit much, this is how you can use the result of .getStackTrace as a string (which can then be printed, put in a log, whatever)

(try (/ 1 0)
  (catch Throwable t
    (map str (.getStackTrace t))))

Sorrows

(apply str (interpose "\n" (.getStackTrace t))) works really well, too. – Titian

Answer 2

use clojure.repl.pst get StackTrace, and binding *err* to java.io.StringWriter:

(use '[clojure.repl :only (pst)])

(defmacro with-err-str
  "Evaluates exprs in a context in which *err* is bound to a fresh
  StringWriter.  Returns the string created by any nested printing
  calls."
  [& body]
  `(let [s# (new java.io.StringWriter)]
     (binding [*err* s#]
       ~@body
       (str s#))))

(try
  (/ 1 0)
  (catch Exception e
    (let [s (with-err-str (pst e 36))]
      (println "Error log:")
      (println s))))

Galingale

Works like a charm. Just that I gad to change the first statement to (use [clojure.repl :only (pst)]) – Pressing

Answer 3

Here's a slight improvement over noisesmith's answer. It doesn't leave a lazy seq and has a beautification feature:

(apply str (interpose "\n" (.getStackTrace t)))

Supposal

Answer 4

You can just use the very useful pr-str function from clojure.core:

(catch Exception e
      (l/error "Ho no, an exception:" (pr-str e)))

#error {
 :cause nil
 :via
 [{:type java.lang.NullPointerException
   :message nil
   :at [my_app$fn__47429$fn__47430 invoke "my_app.clj" 30]}]
 :trace
 [[my_app$fn__47429$fn__47430 invoke "my_app.clj" 30]
  [my_app$my_func invokeStatic "my_app.clj" 13]
  [my_app$my_func invoke "my_app.clj" 10]
  [my_app$other_func$fn__29431 invoke "my_app.clj" 19]
  [my_app$other_func_BANG_ invokeStatic "my_app.clj" 28]
  [my_app$other_func_BANG_ invoke "my_app.clj" 27]
  [my_app$yet_another_func invokeStatic "my_app.clj" 40]
  [my_app$yet_another_func invoke "my_app.clj" 37]
  [clojure.core$fn__8072$fn__8074 invoke "core.clj" 6760]
  [clojure.core.protocols$iter_reduce invokeStatic "protocols.clj" 49]
  [clojure.core.protocols$fn__7839 invokeStatic "protocols.clj" 75]
  [clojure.core.protocols$fn__7839 invoke "protocols.clj" 75]
  [clojure.core.protocols$fn__7781$G__7776__7794 invoke "protocols.clj" 13]
  [clojure.core$reduce invokeStatic "core.clj" 6748]
  [clojure.core$fn__8072 invokeStatic "core.clj" 6750]
  [clojure.core$fn__8072 invoke "core.clj" 6750]
  [clojure.core.protocols$fn__7860$G__7855__7869 invoke "protocols.clj" 175]
  [clojure.core$reduce_kv invokeStatic "core.clj" 6776]
  [clojure.core$reduce_kv invoke "core.clj" 6767]
  [my_app$yet_another_func invokeStatic "data_streamer.clj" 48]
  [my_app$yet_another_func invoke "data_streamer.clj" 47]
  [my_app$other_func invokeStatic "data_streamer.clj" 66]
  [my_app$other_func invoke "data_streamer.clj" 58]
  [my_app$other_func$fn__48385 invoke "my_app.clj" 73]
  [clojure.core.async$thread_call$fn__6553 invoke "async.clj" 442]
  [clojure.lang.AFn run "AFn.java" 22]
  [java.util.concurrent.ThreadPoolExecutor runWorker "ThreadPoolExecutor.java" 1135]
  [java.util.concurrent.ThreadPoolExecutor$Worker run "ThreadPoolExecutor.java" 635]
  [java.lang.Thread run "Thread.java" 844]]}

Votaw

Answer 5

There is also clojure.stacktrace which has print-stack-trace, print-trace-element and some other helpful functions.

Unvoice

Answer 6

you can use with-out-str

(try
  (name nil)
  (catch Exception e
    (with-out-str (println e))))

Pollaiuolo