sample showing how to read from classpath in JAR

foobar.java

package com.example.foobar;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

@RestController
@RequestMapping("/foo")
public class FooController {

    // https://www.baeldung.com/spring-classpath-file-access
    @Autowired
    ResourceLoader resourceLoader;

    @GetMapping
    public ResponseEntity<?> random() {
        List<String> a = new ArrayList<>();
        Random rand = new Random();
        try {
            Resource resource = resourceLoader.getResource("classpath:mikey/my-config.txt");

            InputStream is = resource.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
            String line;
            while ((line = reader.readLine()) != null) {
//                System.out.println(line);
                a.add(line);
            }
            // Close the file
            reader.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        int index = rand.nextInt(a.size());
        String s = a.get(index);
        return ResponseEntity.ok(s);
    }
}