diff --git a/TIL/240221.md b/TIL/240221.md
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+# 240221 Custom Exception Handling (@(Rest)ControllerAdvice, @ExceptionHandler)
+
+```json
+{
+    "timestamp": "2024-02-21T00:45:12.820+00:00",
+    "status": 400,
+    "error": "Bad Request",
+    "trace": "org.springframework.web.bind.MethodArgumentNotValidException: 
+    ...
+    "message": "Validation failed for object='memberDto'. Error count: 1",
+    "errors": [
+        {
+            "codes": [
+                "NotEmpty.memberDto.name",
+                "NotEmpty.name",
+                "NotEmpty.java.lang.String",
+                "NotEmpty"
+            ],
+            "arguments": [
+                {
+                    "codes": [
+                        "memberDto.name",
+                        "name"
+                    ],
+                    "defaultMessage": "name",
+                    "code": "name"
+                }
+            ],
+            "defaultMessage": "name is required",
+            "objectName": "memberDto",
+            "field": "name",
+            "bindingFailure": false,
+            "code": "NotEmpty"
+        }
+    ],
+    "path": "/member"
+}
+```
+=> 이렇게 원하는 리턴 모양을 만들어서 내려주자
+```java
+@ControllerAdvice
+public class CustomExceptionHandler {
+
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ResponseEntity<String> handleMethodArgumentNotValid(MethodArgumentNotValidException ex) {
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("name is required");
+    }
+}
+```
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diff --git a/TIL/240226.md b/TIL/240226.md
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+# 240226 @Valid Nested Dto 검증
+
+## 겪은 문제
+- @Valid 어노테이션을 사용하는데, Nested Dto에 대한 validation이 안됐다!!
+
+
+## 해결 방법 예시 코드
+
+```java
+class MemberController {
+    @PostMapping("/member")
+    public ResponseEntity<MemberDto> createMember(@Valid @RequestBody MemberDto memberDto) {
+        return ResponseEntity.ok(memberService.createMember(memberDto));
+    }
+}
+```
+
+```java
+class MemberDto {
+    @NotEmpty(message = "name is required")
+    String name;
+    @Valid // Nested Dto 검증하기 위해서 @Valid 어노테이션 추가!!!!
+    List<TeamDto> teamDto;
+}
+```
+
+```java
+class TeamDto {
+    @NotEmpty(message = "team name is required")
+    String name;
+}
+```
+
+이렇게 멤버 변수에 @Valid 걸어주면 teamDto에 대한 validation도 수행된다:)
+
+### Reference
+https://medium.com/sjk5766/valid-vs-validated-%EC%A0%95%EB%A6%AC-5665043cd64b
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