Running an R-Program from Java

Question

I got following simple R-program named hello.R:

print('hello')

I like to call this code from Java now. This is my code in Java:

import java.io.IOException;

public class Main {

    public static void main(String[] args) {
        String path = "C:\\Users\\Administrator\\Desktop\\hello.R";
        try {
            Runtime.getRuntime().exec("C:\\Program Files\\R\\R-3.1.3\\bin\\Rscript "+path);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 

    }

}

I was expecting it to print the hello statement in the Java concole. But Java program didn't do anything at all.

Do you know what the problem may be?

You are concatenating an absolute path (path) with another absolute path in Runtime.exec() - even without a path separator! — Nikos Paraskevopoulos
– Nikos Paraskevopoulos, Commented Jan 15, 2016 at 11:09
I got this hint from a different post: stackoverflow.com/questions/8844451/calling-r-script-from-java — XerXes
– XerXes, Commented Jan 15, 2016 at 11:27
Yes, my bad, I am sorry. Did not notice the space and that you are actually calling the interpreter with the path as argument. — Nikos Paraskevopoulos
– Nikos Paraskevopoulos, Commented Jan 15, 2016 at 12:09

rinde · Accepted Answer · 2016-01-15 16:11:50Z

0

Based on this answer I think you should do the following:

ProcessBuilder pb = new ProcessBuilder("/path/to/Rscript", "/path/to/hello.r");
pb.redirectOutput(Redirect.INHERIT);
pb.redirectError(Redirect.INHERIT);
Process p = pb.start();

This redirects both the output stream and the error stream of the subprocess to the current process, allowing you to observe the contents in the Java console.

edited Jan 15, 2016 at 16:11

answered Jan 15, 2016 at 12:52

rinde

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3 Comments

XerXes Over a year ago

I tried this, but unfortunately I get an error message: java.io.IOException: Cannot run program "C:\Program Files\R\R-3.1.3\bin\Rscript C:\Users\Administrator\Desktop\hello.R": CreateProcess error=2, The system cannot find the file specified at java.lang.ProcessBuilder.start(Unknown Source) at Main.main(Main.java:12) Caused by: java.io.IOException: CreateProcess error=2, The system cannot find the file specified at java.lang.ProcessImpl.create(Native Method) at java.lang.ProcessImpl.<init>(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 2 more

rinde Over a year ago

There was a mistake in my code example (the command and its argument need to be separated), I updated my answer.

rinde Over a year ago

Are you sure that the paths you used are correct? You can try the command using Windows command line CMD (assuming you run Windows)?

Volokh · Accepted Answer · 2018-02-19 09:20:17Z

0

You could try the following to get the hello string in Java:

#* @get /hello
hello <- function() {
  print("hello")
}

You can run the following:

library(plumber)
r <- plumb("hello.R")
r$run(port=8080)

If you then call the page

http://localhost:8080/hello

your R code will be executed.

If you want to execute it from Java the solution could be:

   URL url = new URL("http://localhost:8080/hello");
   URLConnection connection = url.openConnection();
   BufferedReader br = new BufferedReader(new InputStreamReader( (connection.getInputStream())));
   String result = br.readLine();

answered Feb 19, 2018 at 9:20

Volokh

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