如何给出文件的相对路径？

Question

When i give the absolute path of twitter.R file it runs correctly. like this:

c.eval("source(\"C:\\\\Users\\\\Ruttab\\\\workspace\\\\RserveConnect\\\\src\\\\main\\\\resources\\\\Script\\\\twitter.R\")");

When i give the relative path it doesnt run and gives me an error. like this:

c.eval("source(\"/src/main/resources/Resources/Rscripts/twitter.R\")");

How to give relative path for the file twitter.R

This is my project hieachy:

Answer 1

String relative = new File(base).toURI().relativize(new 
File(path).toURI()).getPath();

add an example:

String path = "/var/caiyongji/tmp/abc.txt";
String base = "/var/caiyongji";
String relative = new File(base).toURI().relativize(new File(path).toURI()).getPath();
// relative == "tmp/abc.txt"

Answer 2

import java.nio.file.Path; import java.nio.file.Paths;

public class Test {

    public static void main(String[] args) {
        Path pathAbsolute = Paths.get("/var/data/stuff/xyz.dat");
        Path pathBase = Paths.get("/var/data");
        Path pathRelative = pathBase.relativize(pathAbsolute);
        System.out.println(pathRelative);
    }

}

Answer 3

You can declare Path with relative paths, but that won't solve your issue. You cannot expect your java process to know the root directory of your source files just like that.

Your project is likely to be built and packaged as a jar (or a war) and the relative path to your resources may change.

The proper solution to your issue is to get it from the classpath, as explained in this answer

Short version : InputStream input = this.getClass().getResourceAsStream("/Resources/Rscripts/twitter.R");