从终端向Clojure应用程序发送消息

问题描述：

如何将消息发送到正在运行的Clojure应用程序？例如，如果我有一个特定的变量或标志，我想在uberjar运行时从终端设置-这可能吗？

How does one send a message to a running clojure application? For example, if I have a particular variable or flag I want to set from the terminal when the uberjar is running - is this possible?

一种方法是读取文件在应用程序中可以更改，但是听起来很笨拙。

One way is to read a file in the application that you can change, but that sounds clunky.

预先感谢！

答

一种方法是让您的应用托管nREPL（网络REPL）。然后，您可以连接到正在运行的应用程序的nREPL并四处乱逛。

One way to do this is by having your application host a nREPL (network REPL). You can then connect to your running app's nREPL and mess around.

例如，您的应用程序可能看起来像这样：

For example, your app may look like this:

(ns sandbox.main
  (:require [clojure.tools.nrepl.server :as serv]))

(def value (atom "Hey!"))

(defn -main []
  (serv/start-server :port 7888)
  (while true
    (Thread/sleep 1000)
    (prn @value)))

正在运行时，您可以 lein repl：从其他地方连接localhost：7888 并更改 value 原子：

While that's running you can lein repl :connect localhost:7888 from elsewhere and change that value atom:

user=> (in-ns 'sandbox.main)
#object[clojure.lang.Namespace 0x12b094cf "sandbox.main"]
sandbox.main=> (reset! value "Bye!")
"Bye!"

此时，您应用的控制台输出应如下所示：

By this time the console output of your app should look like this:

$ lein run
"Hey!"
"Hey!"
<...truncated...>
"Bye!"
"Bye!"

在JVM上进行进程间通信的选项很多，但这是Clojure独有的方法。

There are many options for interprocess communication on the JVM, but this approach is unique to Clojure.

从终端向Clojure应用程序发送消息

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