feat: LocalDateTime / OffsetDateTime을 ISO 8601 형식으로 직렬화하는 ObjectMapper 모듈 추가

src/main/kotlin/roomescape/common/config/JacksonConfig.kt

@@ -14,16 +14,21 @@ import org.springframework.context.annotation.Bean
 import org.springframework.context.annotation.Configuration
 import roomescape.common.exception.CommonErrorCode
 import roomescape.common.exception.RoomescapeException
-import java.time.LocalDate
+import java.time.*
-import java.time.LocalTime
 import java.time.format.DateTimeFormatter
 
 @Configuration
 class JacksonConfig {
 
+    companion object {
+        private val ISO_OFFSET_DATE_TIME_FORMATTER: DateTimeFormatter =
+            DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssXXX")
+    }
+
     @Bean
     fun objectMapper(): ObjectMapper = ObjectMapper()
         .registerModule(javaTimeModule())
+        .registerModule(dateTimeModule())
         .registerModule(kotlinModule())
         .registerModule(longIdModule())
         .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
@@ -52,6 +57,12 @@ class JacksonConfig {
         simpleModule.addDeserializer(Long::class.java, StringToLongDeserializer())
         return simpleModule
     }
+
+    private fun dateTimeModule(): SimpleModule {
+        val simpleModule = SimpleModule()
+        simpleModule.addSerializer(LocalDateTime::class.java, LocalDateTimeSerializer())
+        simpleModule.addSerializer(OffsetDateTime::class.java, OffsetDateTimeSerializer())
+        return simpleModule
     }
 
     class LongToStringSerializer : JsonSerializer<Long>() {
@@ -77,3 +88,28 @@ class StringToLongDeserializer : JsonDeserializer<Long>() {
             }
         }
     }
+
+    class LocalDateTimeSerializer : JsonSerializer<LocalDateTime>() {
+        override fun serialize(
+            value: LocalDateTime,
+            gen: JsonGenerator,
+            serializers: SerializerProvider
+        ) {
+            value.atZone(ZoneId.systemDefault())
+                .toOffsetDateTime()
+                .also {
+                    gen.writeString(it.format(ISO_OFFSET_DATE_TIME_FORMATTER))
+                }
+        }
+    }
+
+    class OffsetDateTimeSerializer : JsonSerializer<OffsetDateTime>() {
+        override fun serialize(
+            value: OffsetDateTime,
+            gen: JsonGenerator,
+            serializers: SerializerProvider
+        ) {
+            gen.writeString(value.format(ISO_OFFSET_DATE_TIME_FORMATTER))
+        }
+    }
+}

src/test/kotlin/roomescape/common/config/JacksonConfigTest.kt

@@ -7,7 +7,10 @@ import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.string.shouldContain
 import java.time.LocalDate
+import java.time.LocalDateTime
 import java.time.LocalTime
+import java.time.OffsetDateTime
+import java.time.ZoneOffset
 
 class JacksonConfigTest(
     private val objectMapper: ObjectMapper = JacksonConfig().objectMapper()
@@ -66,4 +69,24 @@ class JacksonConfigTest(
             deserialized shouldBe number
         }
     }
+
+    context("OffsetDateTime은 ISO 8601 형식으로 직렬화된다.") {
+        val date = LocalDate.of(2025, 7, 14)
+        val time = LocalTime.of(12, 30, 0)
+        val dateTime = OffsetDateTime.of(date, time, ZoneOffset.ofHours(9))
+        val serialized: String = objectMapper.writeValueAsString(dateTime)
+
+        test("OffsetDateTime 직렬화") {
+            serialized shouldBe "\"2025-07-14T12:30:00+09:00\""
+        }
+    }
+
+    context("LocalDateTime은 ISO 8601 형식으로 직렬화된다.") {
+        val dateTime = LocalDateTime.of(2025, 7, 14, 12, 30, 0)
+        val serialized: String = objectMapper.writeValueAsString(dateTime)
+
+        test("LocalDateTime 직렬화") {
+            serialized shouldBe "\"2025-07-14T12:30:00+09:00\""
+        }
+    }
 })