Getting 404 Not Found for basic spring rest api tutorial - 'hello world' - spring

Question

I am trying to create a rest api web application that can be eventually deployed into a container environment. I downloaded quite a few tutorials from spring.io to other websites as well but each time I use the exact repos I get a 404 error for the simple request.
To simplify it further I reduced it to 2 classes in one package:
project hierarchy
Main class:
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
#SpringBootApplication
public class Main {
public static void main(String[] args) {
SpringApplication.run(Main.class, args);
}
}
Controller Class:
#RestController
#RequestMapping("/")
public class RESTController {
private final AtomicLong counter = new AtomicLong();
private static final String template = "Hello, %s!";
/*
* REST API Test Methods
*/
#RequestMapping( "/greeting" )
public String greeting() {
return "It's working...!";
}
And of course the actual request:
http://localhost:8080/test_rest_api/greeting
HTTP Status 404 – Not Found
Type Status Report
Message /test_rest_api/greeting
Description The origin server did not find a current representation for the target resource or is not
willing to disclose that one exists.
Apache Tomcat/8.5.43
That is running on server by Run As - ; if I select Run as java application and select springboot the following error occurs:
java.lang.IllegalArgumentException: Sources must not be empty at
org.springframework.util.Assert.notEmpty(Assert.java:467)

Answer 1

I finally figured it out and it was a stupid mistake. I added the name of the project as part of the domain of the request url.
http://localhost:8080/test_rest_api/greeting
vs
http://localhost:8080/greeting