Execute .jar file from a Java program

How could I run a local jar file from a java program?

The jar file is not in the class-path of the Java caller program.

Solution 1:

I suggest you use a ProcessBuilder and start a new JVM.

Here is something to get you started:

ProcessBuilder pb = new ProcessBuilder("/path/to/java", "-jar", "your.jar");
pb.directory(new File("preferred/working/directory"));
Process p = pb.start();

Solution 2:

    Process proc = Runtime.getRuntime().exec("java -jar Validate.jar");
    proc.waitFor();
    // Then retreive the process output
    InputStream in = proc.getInputStream();
    InputStream err = proc.getErrorStream();

    byte b[]=new byte[in.available()];
    in.read(b,0,b.length);
    System.out.println(new String(b));

    byte c[]=new byte[err.available()];
    err.read(c,0,c.length);
    System.out.println(new String(c));

Solution 3:

Another way to do on windows is:

Runtime.getRuntime().exec("cmd /c start jarFile");

this way you can set priority of your process as well (normal/low/etc)

Solution 4:

First, the description of your problem is a bit unclear. I don't understand if you want to load the classes from the jar file to use in your application or the jar contains a main file you want to run. I will assume it is the second.

If so, you have a lot of options here. The simplest one would be the following:

String filePath; //where your jar is located.
Runtime.exec(" java -jar " + filepath);

Voila... If you don't need to run the jar file but rather load the classes out of it, let me know.