Executing a Jar file from an Java application

Question

I have 2 methods I wrote to try and execute a Jar file from my Java application and they both are not doing anything. The Java Runtime Environment is installed on the C: drive and by default its Path points to a directory on the C: drive. The Jar file I am trying to execute is located on the E: drive.

Jar location: E:\Demo Folder\MyDemo.jar

I tried to execute MyDemo.jar using the following 2 methods:

Method 1:

try { Runtime.getRuntime().exec("cmd /c start %SystemDrive%\\java -jar " + "E:/Demo Folder/MyDemo.jar"); } catch (IOException ex) { System.err.println(ex.getMessage()); }

Method 2:

try { File dirFile = new File("E:/Demo Folder/"); ProcessBuilder pb = new ProcessBuilder("java", "-jar", "E:/Demo Folder/MyDemo.jar"); pb.directory(dirFile); Process p = pb.start(); } catch (Exception ex) { System.err.println(ex.getMessage()); }

Try to do it like this: stackoverflow.com/questions/4936266/… — sorencito
– sorencito, Commented Dec 12, 2012 at 19:28
I would do that but I do not know always know what version of java is installed and to what location. In his example his got /path/to/java — jadrijan
– jadrijan, Commented Dec 12, 2012 at 19:30
Then try to read the path to Java from the system properties. Should be Java.home — sorencito
– sorencito, Commented Dec 12, 2012 at 19:32
Just a guess, but could it be you need to set the environment variable for the project (assuming you are using Eclipse). In other words I bet the second one would work if you ran your app from the command line. — Jacob Schoen
– Jacob Schoen, Commented Dec 12, 2012 at 19:34

leonbloy · Accepted Answer · 2012-12-12 20:09:26Z

Didn't you try to put your invocation logic inside a, say, E:/Demo Folder/rundemo.bat` (or .cmd) file, and call that .bat from your java instead? That's usually more sane and easy to troubleshoot.

Zagrev · Accepted Answer · 2012-12-12 21:05:10Z

I'm guessing the problem is the space in the path of the jar file. Try this:

new ProcessBuilder("java", "-jar", "\"E:/Demo Folder/MyDemo.jar\"");

initramfs · Accepted Answer · 2013-08-04 19:25:47Z

To launch a external java executable application you must first locate the java.exe file (Which loads the JVM) and pass the argument of -jar to indicate loading of a executable JAR file. In both methods you provided you had minor errors within your code.

In method one:

cmd /c start %SystemDrive%\\java -jar

%SystemDrive% is being treated as a string literal as java is unaware of Windows specific environment variables.

In method two:

"java", "-jar", "E:/Demo Folder/MyDemo.jar"

You are assuming that java.exe has been added to PATH environmental variables which may not be the case. Also, from your usage of the "%" operators, I am assuming you are on a windows machine, which uses \ for directories therefore... "E:/Demo Folder/MyDemo.jar" may not return a valid location.

Try the following segment of code:

try { File dirFile = new File("E:\\Demo Folder\\"); ProcessBuilder pb = new ProcessBuilder(System.getProperty("java.home") + File.separator + "bin" + File.separator + "java", "-jar", new File(dirFile, "MyDemo.jar").getAbsolutePath()); pb.directory(dirFile); Process p = pb.start(); } catch (Exception ex) { System.err.println(ex.getMessage()); }

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