java - 线程在终止之前不会输出流

Question

这个问题已经有答案了:

Java exec method, how to handle streams correctly (2 个回答)

已关闭 4 年前。

我正在尝试打印运行外部 jar 的实时输出，它在线程中运行并且 jar 确实得到执行，问题是输出在线程终止之前不会打印。

public void run() {
    Process proc = null;
    try {

        proc = Runtime.getRuntime().exec("java -jar A.jar");    
        InputStream in = proc.getInputStream();
        InputStream err = proc.getErrorStream();

        BufferedInputStream bis = new BufferedInputStream(in);
        BufferedInputStream bes = new BufferedInputStream(err);

        String iss = IOUtils.toString(in, "UTF8");
        String ess = IOUtils.toString(err, "UTF8");

        System.out.println(iss);
        System.out.println(ess);

    } catch (IOException e) {
        e.printStackTrace();
        this.interrupt();
    }
}

Answer 1

您需要在单独的线程中运行它们，以便同时读取它们。

public void run() {
    try {
        Process proc = Runtime.getRuntime().exec("/home/martin/test.py");
        InputStream in = proc.getInputStream();
        InputStream err = proc.getErrorStream();

        Thread tIn = new Thread(() -> {
            try {
                while (true) {
                    int ch;
                    ch = in.read();
                    if (ch < 0)
                        break;
                    System.out.print((char) ch);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        });

        Thread tErr = new Thread(() -> {
            try {
                while (true) {
                    int ch;
                    ch = err.read();
                    if (ch < 0)
                        break;
                    System.err.print((char) ch);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        });

        tIn.start();
        tErr.start();

        try {
            tIn.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        try {
            tErr.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // this.interrupt();
    } catch (IOException e) {
        e.printStackTrace();
        // this.interrupt();
    }
}

这是单个函数中快速而肮脏的版本。当然，最好编写一个包装该功能的类。