parent 进程和 child 进程之间的通信

Question

我有一个 class 作为 parent 进程。在其运行期间，它创建了许多 child 进程并同时运行s 它们。每个 child 进程基本上都是一个连接到服务并从中提取数据的 HTTP 客户端。

目前，如果 child 进程之一因任何原因停止工作，parent 通过重新启动同一个 child 进程来处理 re-establishing 连接。

child 进程断开连接可能是由多种原因引起的。我想将 child 进程断开连接的原因传达给 parent 进程，并让 parent 进程根据断开连接的原因（套接字读取失败，404 未找到）采取相应行动, 401 未经授权等）。

可能吗？ shortest/best 的方法是什么？这是我的 Parent class:

public class Parent {
public static void main(String[] args){
    List<Process> PRlist = new ArrayList<Process>();
    List<String[]> commandsList = new ArrayList<String[]>();
    DateTimeFormatter frmt = DateTimeFormatter.ofPattern("hh:mm:ss");

    if (args.length == 2 && args[0].matches("-f")){
        String dir = System.getProperty("user.dir");
        String path = dir + "/" + args[1];
        try {
            FileReader fr = new FileReader(path);
            BufferedReader bf = new BufferedReader(fr);

            String line = "";
            while ((line = bf.readLine()) != null){
                String[] tk = line.split(" ");
                String[] cmd = {"java", "-jar", "Child.jar", "-a", tk[0], "-p", tk[1],
                        "-u", tk[2], "-pw", tk[3], "-m", tk[4], "-s", tk[5]};
                Process pr = new ProcessBuilder().inheritIO().command(cmd).redirectInput(Redirect.INHERIT).start();
                PRlist.add(pr); commandsList.add(cmd);
            }
        } 
        catch (FileNotFoundException ex) {ex.printStackTrace();} 
        catch (IOException ex) {ex.printStackTrace();}

        int streamnum = PRlist.size();

        while (true){
            for (int i = 0; i < streamnum; i++){
                if (!PRlist.get(i).isAlive()){
                    PRlist.get(i).destroy();
                    PRlist.remove(i);
                    try {
                        Process PR = new ProcessBuilder().inheritIO().command(commandsList.get(i)).redirectInput(Redirect.INHERIT).start();
                        System.out.println(commandsList.get(i)[12] + " stream re-established at " + LocalDateTime.now().format(frmt));
                        PRlist.add(i,PR);
                    } catch (IOException ex) {ex.printStackTrace();}
                }
            }

            try {
                Thread.sleep(5000);
            } catch (InterruptedException ex) {ex.printStackTrace();}
        }
    } else {
        System.out.println("No stream file was specified.");
    }
}}

如有任何帮助，我们将不胜感激。

Answer 1

也许你可以使用这些方法

**public ProcessBuilder.Redirect redirectError()**
Returns this process builder's standard error destination. Subprocesses   subsequently started by this object's start() method redirect their standard error to this destination. The initial value is Redirect.PIPE.
Returns:
this process builder's standard error destination

或者

public abstract int exitValue()
Returns the exit value for the subprocess.
Returns:
the exit value of the subprocess represented by this Process object. By convention, the value 0 indicates normal termination.
Throws:
IllegalThreadStateException - if the subprocess represented by this Process object has not yet terminated

Answer 2

举个例子

有点像

if (!PRlist.get(i).isAlive()){
    int exitCode=PRlist.get(i).exitValue();
    //Do something with exitValue

    PRlist.get(i).destroy();
    PRlist.get(i).destroy();
    PRlist.remove(i);
    try {
        Process PR = new ProcessBuilder().inheritIO().command(commandsList.get(i)).redirectInput(Redirect.INHERIT).start();
        System.out.println(commandsList.get(i)[12] + " stream re-established at " + LocalDateTime.now().format(frmt));
         PRlist.add(i,PR);
         } catch (IOException ex) {ex.printStackTrace();}
         }

带有 errorStream 的示例可能更复杂，但我们的想法是查看通过文本处理在 errorStream 中发布的异常。

Answer 3

好的，对于 Java 个线程，您可以这样做：

class MyThreadedApp {

    // main() here

    /**
     * Starting a new thread
     */
    private void start() {
        new Thread(() -> {
            try {
                new Worker().run();
            } catch (Exception ex) {
                threadEnded(ex);
            }
        }).start();
    }

    /**
     * Handle errors
     * 
     * @param ex Error
     */
    private void threadEnded(Exception ex) {
        System.out.println(ex.getMessage());
    }
}

/**
 * My worker thread
 */
class Worker {

    void run() throws IOException {
        // Do my stuff here
    }
}

这是一个基本示例，仅用于演示数据流。在实践中，您可以使用 @lscoughlin 提到的技术。

parent 进程和 child 进程之间的通信

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