JVM子进程

Question

为什么在JVM退出时子进程死掉？我尝试了许多不同的方法，但都没有成功。我以为这个过程会独立完成。

Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                try {
                    logger.info("Attempting to restart using\n" + cmd.toString());
                    ProcessBuilder pb = new ProcessBuilder("/opt/jdk1.8.0_121/bin/java" ,
                                                            "-Xms64m",
                                                            "-Xmx128m",
                                                            "-jar",
                                                            "/usr/share/pdfconverter-service/bin/pdfconverter-service.jar",
                                                            "--spring.config.location=/usr/share/pdfconverter-service/conf/application.properties");
                    pb.redirectOutput(logFile);
                    pb.redirectError(logFile);
                    pb.redirectErrorStream(true);
                    Process p = pb.start();
                    logger.info("Restart Initiated");
                } catch (IOException  e ) {
                    logger.error("Error restarting application", e);
                    logger.error(e.toString(), e);
                }
            }
        });
        // execute some custom code before restarting
        if (runBeforeRestart != null) {
            runBeforeRestart.run();
        }
        // exit
        System.exit(0);