AppEndpointController.java

package testapp;

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.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/app")
public class AppEndpointController {

    @GetMapping
    public ResponseEntity<String> getHello(
        @RequestParam(value = "name", defaultValue = "") String name
    ) {
        return ResponseEntity
            .status(200)
            .body(name.isEmpty() ? "Hello" : "Hello, " + name + "!");
    }

}