exception-handling - 尝试和弹弓/尝试+的区别？

Question

我正在尝试为clj-http返回404时编写一个异常处理程序。根据documentation中的Exceptions部分:

clj-http will throw a Slingshot Stone that can be caught by a regular (catch Exception e ...) or in Slingshot's try+ block

尝试此操作，似乎有些差异我很难弄清楚:

(ns my-app.core
  (:require [clj-http.client :as client])
  (:use [slingshot.slingshot]))

(try
  (client/get "http://some-site.com/broken")
  (catch Exception e (print "I found a problem!")))

=> I found a problem!
   nil

(try+
  (client/get "http://some-site.com/broken")
  (catch Exception e (print "I found a problem!")))

=> ExceptionInfo clj-http: status 404  clj-http.client/wrap-exceptions/fn--1604 (client.clj:147)

Answer 1

如果您不筛选Exception的子类，则可以正常工作:

(try+
  (client/get "http://some-site.com/broken")
  (catch Object _ (print "I found a problem!")))

这里抛出的是带有异常元数据的本地Clojure映射，而不是传统的Java异常。

这样，如果您使用的是Slingshot，则可以在该 map 上进行过滤-使用诸如请求状态，返回的内容，重定向等字段-以使除了块以外的其他块具有比类更多的细粒度选择。例如:

(try+
  (client/get "http://some-site.com/broken")
  (catch [:status 404] {:keys [trace-redirects]}
    (print "No longer exists! (redirected through " trace-redirects ")")))