add file upload service

src/main/java/io/github/devopsws/demo/service/FileService.java

@@ -0,0 +1,22 @@
+package io.github.devopsws.demo.service;
+
+@RestController
+@RequestMapping("/upload")
+public class FileService {
+    @Postmapping("/")
+    public Message<?> upload(@RequestParam("file") MultipartFile file) {
+        Message<String> message = new Message<String>();
+        if (!file.isEmpty()) {
+            try {
+                System.out.println("Uploading file size:" + file.length());
+
+                message.setMessage("ok");
+            } catch (Exception e) {
+                message.setMessage(e.getMessage());
+            }
+        } else {
+            rmessage.setMessage("file is empty");
+        }
+        return message
+    }
+}