添加了hello Controller

src/main/java/org/example/docker_project/Controller/HelloController.java

@@ -0,0 +1,15 @@
+package org.example.docker_project.Controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class HelloController
+{
+    @GetMapping("/")
+    public String index()
+    {
+        return "Hello World!";
+    }
+}
+