CODEWITHSUNDEEP
javaprocessbuilder
Dhiren Hamal
Dhiren Hamal

Reputation: 1012

Pass object as parameter in ProcessBuilder?

I want to pass two or more object as parameter into the ProcessBuilder for the purpose of run program as seprate process. I tried the following code but it doesn't work.

public static int exec(FTP ftp, Stage stage) throws IOException,
                                               InterruptedException {
        String javaHome = System.getProperty("java.home");
        String javaBin = javaHome +
                File.separator + "bin" +
                File.separator + "java";
        String classpath = System.getProperty("java.class.path");
        String className = Test.class.getCanonicalName();

        ProcessBuilder builder = new ProcessBuilder(
                javaBin, "-cp", classpath, className+" "+ftp+" "+stage);

        Process process = builder.start();
        process.waitFor();
        return process.exitValue();
    }

And Here is the Test.class

public class Test extends Application
{
    String lol = "000";
    public Test(FTP ftp, Stage stage)
    {
        // The logic goes here for those passed parameter
        System.out.println("This is Test");
    }

    @Override
    public void start(Stage arg0) throws Exception 
    {
        // TODO Auto-generated method stub
        arg0.setTitle("Hello there");
        arg0.setWidth(200);
        arg0.setHeight(200);

        arg0.setScene(new Scene(new Pane(new Label(lol)),1000,1000));
        arg0.show();
    }
}

Here Test class is not executing but If I remove those two parameter then only it works. Can somene please tell me how to pass object as parameter?

Upvotes: 0

Views: 2128

Answers (3)

Amrit Shrestha
Amrit Shrestha

Reputation: 1660

ProcessBuilder can only help you when you want to run a java program as seprate process. It is not possible to pass the object parameter into the ProcessBuilder. Between the two different processes you can not directly pass the paramater. For that you can store those object into the file or can pass object through the pipe.

Upvotes: 1

Daniel Pryden
Daniel Pryden

Reputation: 60997

No, you cannot pass an instance object across a process boundary (well, OK, there is shared memory, but you can't use that in Java, and it's often not the right solution in C either). What you can do is pass messages between processes. Command line arguments are one way, but as you have found they're limited to data that can be serialized as strings.

The other alternative would be to serialize your objects and deserialize them in the child process. For example, you could open an ObjectOutputStream from the parent to the child's stdin and send arbitrarily complex objects through that. The objects you'd get on the other side would still be copies, though, not the same object identity as the objects in the parent process.

Upvotes: 2

Adam Michalik
Adam Michalik

Reputation: 9965

When you start a new process, it does not share any data with the parent process. That is the same as if you invoked the child process from the command line.

The only information you can provide to the child process are the ones that are accepted (understood) by that process as invocation parameters and they have to be provided as strings. The child process needs to interpret the invocation parameters and create the required objects by parsing them.

In your case - you need to provide all the important information about ftp and stage so that the new process can recreate the instances. Even then, these will be totally new objects owned by the new process, independent from the ones of the parent process.

Upvotes: 1

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