Feature: 정답 제출 POST API 멱등성 처리 (#25)

* feat: 정답 제출 API 멱등성 구현

- 커스텀 필터를 통한 서블릿 응답 래핑
- 인터셉터와 캐시를 이용한 멱등성 DB 구현

* feat: 키가 존재하지 않는 경우 스킵

* feat: 인터셉터에서 반환하는 형식 및 로그 수정

* refactor: 멱등성 관련 클래스 패키지 분리

src/main/java/org/cotato/csquiz/common/config/WebConfig.java

@@ -0,0 +1,22 @@
+package org.cotato.csquiz.common.config;
+
+import lombok.RequiredArgsConstructor;
+import org.cotato.csquiz.common.idempotency.IdempotencyInterceptor;
+import org.cotato.csquiz.common.idempotency.IdempotencyRedisRepository;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Configuration
+@RequiredArgsConstructor
+public class WebConfig implements WebMvcConfigurer {
+
+    private final IdempotencyRedisRepository idempotencyRedisRepository;
+
+    @Override
+    public void addInterceptors(InterceptorRegistry registry) {
+        registry.addInterceptor(new IdempotencyInterceptor(idempotencyRedisRepository))
+                .addPathPatterns("/v1/api/record/reply")
+                .order(1);
+    }
+}

src/main/java/org/cotato/csquiz/common/error/ErrorCode.java

@@ -52,10 +52,12 @@ public enum ErrorCode {
     CONTENT_IS_ALREADY_ANSWER(HttpStatus.BAD_REQUEST, "Q-303", "이미 정답인 답을 추가했습니다"),
     QUIZ_ACCESS_DENIED(HttpStatus.BAD_REQUEST, "Q-401", "해당 퀴즈는 아직 접근할 수 없습니다."),
     QUIZ_TYPE_NOT_MATCH(HttpStatus.BAD_REQUEST, "Q-402", "주관식 정답만 추가 가능합니다."),
-
+
+    KING_MEMBER_EXIST(HttpStatus.CONFLICT, "K-301", "이미 킹킹 멤버가 존재합니다"),
+
     SUBJECT_INVALID(HttpStatus.BAD_REQUEST, "E-000", "교육 주제는 NULL이거나 비어있을 수 없습니다."),
 
-    KING_MEMBER_EXIST(HttpStatus.CONFLICT, "K-301", "이미 킹킹 멤버가 존재합니다"),
+    PROCESSING(HttpStatus.CONFLICT, "D-999", "해당 키의 요청은 아직 처리 중 입니다."),
 
     ALREADY_REPLY_CORRECT(HttpStatus.BAD_REQUEST, "R-301", "해당 사용자는 이미 정답 처리되었습니다."),
 

src/main/java/org/cotato/csquiz/common/idempotency/CustomServletWrappingFilter.java

@@ -0,0 +1,23 @@
+package org.cotato.csquiz.common.idempotency;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
+import org.springframework.web.util.ContentCachingResponseWrapper;
+
+@Component
+public class CustomServletWrappingFilter extends OncePerRequestFilter {
+    @Override
+    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
+            throws ServletException, IOException {
+
+        final ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(response);
+        filterChain.doFilter(request, responseWrapper);
+
+        responseWrapper.copyBodyToResponse();
+    }
+}

src/main/java/org/cotato/csquiz/common/idempotency/IdempotencyInterceptor.java

@@ -0,0 +1,71 @@
+package org.cotato.csquiz.common.idempotency;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.cotato.csquiz.common.error.ErrorCode;
+import org.cotato.csquiz.common.error.response.ErrorResponse;
+import org.springframework.http.HttpStatus;
+import org.springframework.stereotype.Component;
+import org.springframework.web.servlet.HandlerInterceptor;
+import org.springframework.web.servlet.ModelAndView;
+import org.springframework.web.util.ContentCachingResponseWrapper;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class IdempotencyInterceptor implements HandlerInterceptor {
+
+    private static final String IDEMPOTENCY_HEADER = "Idempotency-Key";
+    private final IdempotencyRedisRepository idempotencyRedisRepository;
+
+    @Override
+    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
+            throws Exception {
+        String idempotencyKey = request.getHeader(IDEMPOTENCY_HEADER);
+        if (idempotencyKey == null) {
+            return true;
+        }
+        ObjectMapper objectMapper = new ObjectMapper();
+
+        if (idempotencyRedisRepository.hasSucceedResult(idempotencyKey)) {
+            response.getWriter()
+                    .write(objectMapper.writeValueAsString(
+                            idempotencyRedisRepository.getSucceedResponse(idempotencyKey)));
+            log.info("[멱등성 DB에 데이터 존재]");
+            return false;
+        }
+
+        if (idempotencyRedisRepository.isProcessing(idempotencyKey)) {
+            response.setStatus(HttpStatus.CONFLICT.value());
+            response.setContentType("application/json; charset=UTF-8");
+            response.getWriter()
+                    .write(objectMapper.writeValueAsString(ErrorResponse.of(ErrorCode.PROCESSING, request)));
+            log.warn("[요청은 왔지만 아직 처리 중]");
+            return false;
+        }
+
+        // 캐시에 결과가 존재하지 않으면 -> 처리중이란 값을 넣고 컨트롤러를 실행함
+        idempotencyRedisRepository.saveStatusProcessing(idempotencyKey);
+        return true;
+    }
+
+    @Override
+    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
+                           ModelAndView modelAndView) throws Exception {
+        String idempotencyKey = request.getHeader(IDEMPOTENCY_HEADER);
+        if (idempotencyKey == null) {
+            return;
+        }
+        ObjectMapper objectMapper = new ObjectMapper();
+
+        final ContentCachingResponseWrapper responseWrapper = (ContentCachingResponseWrapper) response;
+
+        idempotencyRedisRepository.saveSucceedResult(idempotencyKey,
+                objectMapper.readTree(responseWrapper.getContentAsByteArray()));
+
+        responseWrapper.copyBodyToResponse();
+    }
+}

src/main/java/org/cotato/csquiz/common/idempotency/IdempotencyRedisRepository.java

@@ -0,0 +1,75 @@
+package org.cotato.csquiz.common.idempotency;
+
+import java.util.concurrent.TimeUnit;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.stereotype.Repository;
+
+@Slf4j
+@Repository
+@RequiredArgsConstructor
+public class IdempotencyRedisRepository {
+
+    private static final String KEY_PREFIX = "$Idempotency ";
+    private static final int RESPONSE_EXPIRATION = 30;
+
+    private final RedisTemplate<String, Object> redisTemplate;
+
+
+    public boolean hasSucceedResult(String idempotencyKey) {
+        String key = KEY_PREFIX + idempotencyKey;
+        IdempotencyResponse response = (IdempotencyResponse) redisTemplate.opsForValue().get(key);
+
+        if (response == null) {
+            return false;
+        }
+        return response.isSucceed();
+    }
+
+    public void saveStatusProcessing(String idempotencyKey) {
+        String key = KEY_PREFIX + idempotencyKey;
+        IdempotencyResponse response = IdempotencyResponse.builder()
+                .processStatus(ProcessStatus.PROCESSING)
+                .build();
+
+        redisTemplate.opsForValue().set(
+                key,
+                response,
+                RESPONSE_EXPIRATION,
+                TimeUnit.MINUTES
+        );
+    }
+
+    public boolean isProcessing(String idempotencyKey) {
+        String key = KEY_PREFIX + idempotencyKey;
+        IdempotencyResponse response = (IdempotencyResponse) redisTemplate.opsForValue().get(key);
+        log.info("[처리 중]");
+        if (response == null) {
+            return false;
+        }
+        return response.isProcessing();
+    }
+
+    public Object getSucceedResponse(String idempotencyKey) {
+        String key = KEY_PREFIX + idempotencyKey;
+        IdempotencyResponse savedData = (IdempotencyResponse) redisTemplate.opsForValue().get(key);
+        return savedData.getResult();
+    }
+
+    public void saveSucceedResult(String idempotencyKey, Object result) {
+        final String key = KEY_PREFIX + idempotencyKey;
+
+        IdempotencyResponse response = IdempotencyResponse.builder()
+                .processStatus(ProcessStatus.SUCCESS)
+                .result(result)
+                .build();
+
+        redisTemplate.opsForValue().set(
+                key,
+                response,
+                RESPONSE_EXPIRATION,
+                TimeUnit.MINUTES
+        );
+    }
+}

src/main/java/org/cotato/csquiz/common/idempotency/IdempotencyResponse.java

@@ -0,0 +1,23 @@
+package org.cotato.csquiz.common.idempotency;
+
+import java.io.Serializable;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+
+@Builder
+@AllArgsConstructor
+@Data
+public class IdempotencyResponse implements Serializable {
+
+    private ProcessStatus processStatus;
+    private Object result;
+
+    public boolean isProcessing() {
+        return this.processStatus == ProcessStatus.PROCESSING;
+    }
+
+    public boolean isSucceed() {
+        return this.processStatus == ProcessStatus.SUCCESS;
+    }
+}

src/main/java/org/cotato/csquiz/common/idempotency/ProcessStatus.java

@@ -0,0 +1,16 @@
+package org.cotato.csquiz.common.idempotency;
+
+import lombok.AllArgsConstructor;
+import org.cotato.csquiz.common.error.ErrorCode;
+
+@AllArgsConstructor
+public enum ProcessStatus {
+
+
+    PROCESSING("현재 해당 요청 처리 중"),
+    SUCCESS("요청 완료")
+
+    ;
+
+    private final String description;
+}