我应该如何从Java应用程序运行NodeJS？ [英] How should I run NodeJS from a Java application?

问题描述

我正在编写一个Java库，实际上是一个Clojure库，但对于这个问题，重要的是它在JVM上运行。这个库需要执行一些JavaScript。 我尝试过Nashorn 但我遇到了一些可能难以克服的限制。作为替代方案，我想尝试NodeJS。

I'm writing a Java library, actually, a Clojure library, but for this question, what matters is that it runs on the JVM. This library needs to execute some JavaScript. I tried with Nashorn but I encounter some limitations that might be too hard to overcome. As an alternative, I want to try NodeJS.

我希望我的库是自包含的，不依赖于独立运行NodeJS的系统，因此需要特定的部署机制将Java和NodeJS工件放在正确的位置，由两个不同的网络服务器拾取。但是，这种方法会带来一些问题。

I want my library to be self contained, to not depend on the system running NodeJS independently and thus requiring a particular deployment mechanism to place the Java and NodeJS artifacts in the right places to be picked up by the two different network servers. This approach, though, brings some issues.

我将通过HTTP与NodeJS交谈，但我不希望NodeJS打开特定端口。我想找一个随机未使用的，所以没有碰撞。我还想控制来自NodeJS的日志的位置，以便将它们与我的应用程序的其余部分保持一致。最后，我的应用程序应该能够检测到NodeJS何时崩溃并重新运行它或报告错误信息。

I will be talking to NodeJS over HTTP but I don't want NodeJS to open a specific port. I want to find a random unused one so there's no collisions. I also want to control where the logs from NodeJS go, as to keep them with the rest of my application. Lastly, my app should be able to detect when NodeJS crashed and re-run it or report an error with information.

最好的方法是什么？是否有任何Java库以这种方式帮助管理子进程？我应该从NodeJS方面做一些特别的事情（我是NodeJS的新手，我之前从未使用过它。）

What's the best way to approach this? Are there any Java libraries to help manage child process in this fashion? Anything in particular I should do from the NodeJS side (I'm very new to NodeJS, I never used it before).

推荐答案

我的解决方案最终是使用这样的ProcessBuilder：

My solution in the end was to use ProcessBuilder like this:

(defn create-process-builder [js-engine]
  (doto (ProcessBuilder. ["node" (:path js-engine)
                          "--port-file" (:port-file js-engine)
                          "--default-ajax-host" (:default-ajax-host js-engine)
                          "--default-ajax-port" (str (:default-ajax-port js-engine))])
    .inheritIO))

然后在其中调用start。 inheritIO导致它的输出转到当前进程的输出，该进程有效地合并了stdout和stderr。

and then call start in it. inheritIO causes the output of it to go to the output of the current process which effectively merges stdout and stderr.

除此之外，NodeJS通过指定0为打开随机端口端口号并将其写入文件：

On top of that NodeJS opens a random port by specifying 0 as the port number and writes it to a file:

(let [app (-> (express)
              (.use (cookie-parser))
              (.get "/" (fn [_req res] (.send res "Universal JavaScript engine for server side pre-rendering single page applications.")))
              (.get "/render" render))
      server (.createServer http app)]
  (.listen server 0 (fn [] (.writeFile fs (:port-file options) (.-port (.address server)))))))))

然后由Java端打开（等待它出现）：

which then is opened by the Java side (waiting for it to appear):

(defn get-port-number [js-engine]
  (or (with-timeout
        (:start-timeout js-engine)
        (loop [port-number (read-port-file js-engine)]
          (if (string/blank? port-number)
            (if (is-running? js-engine)
              (do (Thread/sleep 100)
                  (recur (read-port-file js-engine)))
              (throw (Exception. (str "While waiting for port number, process died: " (:path js-engine)))))
            port-number)))
      (throw (Exception. (str "Waited for " (:start-timeout js-engine) " for " (:path js-engine) " to start and report its port number but it timed out.")))))

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