try
The exprs are evaluated and, if no exceptions occur, the value of the last is returned. If an exception occurs and catch clauses are provided, each is examined in turn and the first for which the thrown exception is an instance of the named class is considered a matching catch clause. If there is a matching catch clause, its exprs are evaluated in a context in which name is bound to the thrown exception, and the value of the last is the return value of the function. If there is no matching catch clause, the exception propagates out of the function. Before returning, normally or abnormally, any finally exprs will be evaluated for their side effects. See http://clojure.org/special_forms for more information.
© Rich Hickey. All rights reserved. Eclipse Public License 1.0
6 Examples
=> (try (/ 1 0) (catch Exception e (str "caught exception: " (.getMessage e)))) "caught exception: Divide by zero"
;; Example with multiple catch clauses and a finally clause. (try (f) (catch SQLException se (prn (.getNextException e))) (catch Exception2 e (prn "Handle generic exception")) (finally (prn "Release some resource")))
;; The catch/finally clause is an implicit do. (try (/ 1 0) (catch Exception ex (.printStackTrace ex) (str "caught exception: " (.getMessage ex)))) ;; java.lang.ArithmeticException: Divide by zero ;; at clojure.lang.Numbers.divide(Numbers.java:163) ;; at clojure.lang.Numbers.divide(Numbers.java:3833) ;; ... ;; at main.java:37) ;;=> "caught exception: Divide by zero"
;; try multiple expressions (try (println "expression 1") (println "expression 2") (/ 1 0) (println "expression 4") (catch Exception e (println "expression 3 throws"))) ;;=> expression 1 ;;=> expression 2 ;;=> expression 3 throws
;; The last value in the body of try will be returned. (try "I will not be returned." "I will be returned" (catch Exception e (.getMessage e)) (finally "I will also not be returned.")) ;; => "I will be returned" ;; If there's an exception the last value in the body of catch will be returned. (try (throw (RuntimeException.)) "I will not be returned" (catch Exception e "I will be returned") (finally "I will also not be returned.")) ;; => "I will be returned"