Linux上的Java执行进程

Question

I've been struggling for a while now with this problem and i can't seem to fix it. i already have tried different approaches (Runtime.exec(), ProcessBuiler) but none seem to work.

This is my issue. I have a laptop which is always on. This laptop runs a java tool connected to an arduino via usb to turn on and off the lights in the house. i have created this program myself, therefore i'm also doing some regular maintenance work on it. Recently i have added a button to restart the program from my html interface (in case i have an update, or if for some other reason i might need to restart the program or i decide to implement auto updating in the near future).

This idea behind this is to start a second instance of the application from the first instance and then System.exit(0) the first instance.

For some reason i'm not able to start a second instance of the application. Here's some code.

public void shutdown(boolean restart) {
        if (this.serial != null) {
            this.serial.disconnect();
        }

        if (restart) {
            System.out.println(this.getClass().getProtectionDomain().getCodeSource().getLocation().getPath());
            String startupCommand = "java -jar \"" + this.getClass().getProtectionDomain().getCodeSource().getLocation().getPath().replace("%20", " ") + "\"";
            ProcessBuilder builder = new ProcessBuilder();

//            String[] command = new String[1];
//            command[0] = "-jar \"" + (System.getProperty("user.dir") + "/Home_Automation_Executor.jar") + "\"";
            try {
//                //System.out.println("Restarting Home Automation with command: " + command[0]);
//                System.out.println("Restarting Home Automation with command: " + startupCommand);
//                Runtime.getRuntime().exec("bash");
//                Process proc = Runtime.getRuntime().exec(startupCommand);
                Process proc = builder.command(startupCommand).start();
                InputStream stderr = proc.getErrorStream();
                InputStreamReader isr = new InputStreamReader(stderr);
                BufferedReader br = new BufferedReader(isr);
                String line = null;
                System.out.println("<ERROR>");
                while ((line = br.readLine()) != null) {
                    System.out.println(line);
                }
                System.out.println("</ERROR>");
                int exitVal = 0;
                try {
                    exitVal = proc.waitFor();
                } catch (InterruptedException ex) {
                    Logger.getLogger(Engine.class.getName()).log(Level.SEVERE, null, ex);
                }
                System.out.println("Process exitValue: " + exitVal);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        System.out.println("Terminating Home Automation");
        System.exit(0);
    }

java.io.IOException: Cannot run program "java -jar "/Users/NightWalker/Dropbox/Development/Source Code/Java/NightWare Tools/Home Automation/Home Automation Executor/dist/Home_Automation_Executor.jar"": error=2, No such file or directory at java.lang.ProcessBuilder.start(ProcessBuilder.java:460) at home.automation.executor.Engine.shutdown(Engine.java:186) at home.automation.executor.webserver.HTTPGenerator._handleActionCommand(HTTPGenerator.java:190) at home.automation.executor.webserver.HTTPGenerator._generateHTTPPage(HTTPGenerator.java:165) at home.automation.executor.webserver.HTTPGenerator.getHTTPPage(HTTPGenerator.java:58) at home.automation.executor.webserver.HTTPRequestHandler.run(HTTPRequestHandler.java:160) Caused by: java.io.IOException: error=2, No such file or directory at java.lang.UNIXProcess.forkAndExec(Native Method) at java.lang.UNIXProcess.(UNIXProcess.java:53) at java.lang.ProcessImpl.start(ProcessImpl.java:91) at java.lang.ProcessBuilder.start(ProcessBuilder.java:453 ) ... 5 more

Answer 1

The problem is this:

String startupCommand = "java -jar \"" + this.getClass().getProtectionDomain().getCodeSource().getLocation().getPath().replace("%20", " ") + "\"";

/* more stuff */ builder.command(startupCommand);

This means Jav will look for a command named java -jar ...stuff with spaces... . But what you want is, that Java looks for a command named java and give that command several parameters.

You should use

/*...*/ builder.command("java", "-jar", jarLocation) /*...*/

Answer 2

Since it is another Java program you might want to consider running it in the same process because it's much easier to communicate between the two programs if they live in the same process. Have you tried running the command outside your program? Does it work? What does the meta-inf.mf file in the jar hold? It might be that the classpath in the meta-inf.mf file isn't relative so any dependent jars can't be found.