spring mvc : http response - message body

spring-mvc/springmvc/src/main/java/com/example/springmvc/basic/response/ResponseBodyController.java

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+package com.example.springmvc.basic.response;
+
+import com.example.springmvc.basic.HelloData;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ResponseBody;
+import org.springframework.web.bind.annotation.ResponseStatus;
+import org.springframework.web.bind.annotation.RestController;
+
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+@Slf4j
+@Controller
+public class ResponseBodyController {
+
+    @GetMapping("/response-body-string-v1")
+    public void responseBodyV1(HttpServletResponse response) throws IOException {
+        response.getWriter().write("ok");
+    }
+
+    @GetMapping("/response-body-string-v2")
+    public ResponseEntity<String> responseBodyV2() {
+        return new ResponseEntity<>("ok", HttpStatus.OK);
+    }
+
+    @ResponseBody
+    @GetMapping("/response-body-string-v3")
+    public String responseBodyV3() {
+        return "ok";
+    }
+
+    @GetMapping("/response-body-json-v1")
+    public ResponseEntity<HelloData> responseBodyJsonV1() {
+        HelloData helloData = new HelloData();
+        helloData.setUsername("userA");
+        helloData.setAge(20);
+        return new ResponseEntity<>(helloData, HttpStatus.OK);
+    }
+
+    @ResponseStatus(HttpStatus.OK)
+    @ResponseBody
+    @GetMapping("/response-body-json-v2")
+    public HelloData responseBodyJsonV2() {
+        HelloData helloData = new HelloData();
+        helloData.setUsername("userA");
+        helloData.setAge(20);
+        return helloData;
+    }
+}