Executing a Java application in a separate process

java process exec
Ande Turner picture Ande Turner · Mar 11, 2009 · Viewed 66.9k times · Source

Can a Java application be loaded in a separate process using its name, as opposed to its location, in a platform independent manner?

I know you can execute a program via ...

Process process = Runtime.getRuntime().exec( COMMAND );

... the main issue of this method is that such calls are then platform specific.


Ideally, I'd wrap a method into something as simple as...

EXECUTE.application( CLASS_TO_BE_EXECUTED );

... and pass in the fully qualified name of an application class as CLASS_TO_BE_EXECUTED.

Answer

hallidave picture hallidave · Apr 7, 2009

This is a synthesis of some of the other answers that have been provided. The Java system properties provide enough information to come up with the path to the java command and the classpath in what, I think, is a platform independent way.

public final class JavaProcess {

    private JavaProcess() {}        

    public static int exec(Class klass, List<String> args) 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 = klass.getName();

        List<String> command = new LinkedList<String>();
        command.add(javaBin);
        command.add("-cp");
        command.add(classpath);
        command.add(className);
        if (args != null) {
            command.addAll(args);
        }

        ProcessBuilder builder = new ProcessBuilder(command);

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

}

You would run this method like so:

int status = JavaProcess.exec(MyClass.class, args);

I thought it made sense to pass in the actual class rather than the String representation of the name since the class has to be in the classpath anyways for this to work.

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