feat : ContextualSerializer 를 사용하는 직렬화 예제 코드 추가

놀이터(예제 코드 작성)/jackson/src/main/kotlin/com/banjjoknim/playground/jackson/common/Cars.kt

@@ -1,5 +1,6 @@
 package com.banjjoknim.playground.jackson.common
 
+import com.banjjoknim.playground.jackson.jsonserialize.ContextualCarSerializer
 import com.banjjoknim.playground.jackson.jsonserialize.UsingJsonSerializeAnnotationCarSerializer
 import com.fasterxml.jackson.databind.annotation.JsonSerialize
 
@@ -16,7 +17,7 @@ data class CarUsingNoAnnotation(
     val owner: Owner = Owner()
 )
 
-data class CarUsingJsonSerializeAnnotation(
+data class CarUsingJsonSerializeAnnotationCarSerializer(
     val name: String = "banjjoknim",
     @JsonSerialize(using = UsingJsonSerializeAnnotationCarSerializer::class)
     val secret: String = "secret",
@@ -24,6 +25,23 @@ data class CarUsingJsonSerializeAnnotation(
     val owner: Owner = Owner()
 )
 
+data class CarUsingContextualSerializerWithSecretAnnotation(
+    val name: String = "banjjoknim",
+    @JsonSerialize(using = ContextualCarSerializer::class)
+    @field:Secret("hello world!!")
+    val secret: String = "secret",
+    val price: Int = 10000000,
+    val owner: Owner = Owner()
+)
+
+data class CarUsingContextualSerializerWithNoSecretAnnotation(
+    val name: String = "banjjoknim",
+    @JsonSerialize(using = ContextualCarSerializer::class)
+    val secret: String = "secret",
+    val price: Int = 10000000,
+    val owner: Owner = Owner()
+)
+
 data class CarUsingSecretAnnotation(
     val name: String = "banjjoknim",
     @field:Secret("****")

놀이터(예제 코드 작성)/jackson/src/main/kotlin/com/banjjoknim/playground/jackson/jsonserialize/CarSerializers.kt

@@ -4,6 +4,8 @@ import com.banjjoknim.playground.jackson.common.Car
 import com.banjjoknim.playground.jackson.common.Secret
 import com.fasterxml.jackson.core.JsonGenerator
 import com.fasterxml.jackson.databind.BeanDescription
+import com.fasterxml.jackson.databind.BeanProperty
+import com.fasterxml.jackson.databind.JsonSerializer
 import com.fasterxml.jackson.databind.SerializationConfig
 import com.fasterxml.jackson.databind.SerializerProvider
 import com.fasterxml.jackson.databind.introspect.Annotated
@@ -12,6 +14,7 @@ import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector
 import com.fasterxml.jackson.databind.module.SimpleModule
 import com.fasterxml.jackson.databind.ser.BeanPropertyWriter
 import com.fasterxml.jackson.databind.ser.BeanSerializerModifier
+import com.fasterxml.jackson.databind.ser.ContextualSerializer
 import com.fasterxml.jackson.databind.ser.std.StdSerializer
 
 /**
@@ -83,6 +86,24 @@ class UsingJsonSerializeAnnotationCarSerializer : StdSerializer<String>(String::
     }
 }
 
+class ContextualCarSerializer(
+    private val substituteValue: String = "this is default value in ContextualCarSerializer"
+) : StdSerializer<String>(String::class.java), ContextualSerializer {
+    override fun serialize(value: String, gen: JsonGenerator, provider: SerializerProvider) {
+        gen.writeString(substituteValue)
+    }
+
+    override fun createContextual(provider: SerializerProvider, property: BeanProperty): JsonSerializer<*> {
+        val annotation = property.getAnnotation(Secret::class.java)
+        if (annotation != null) {
+            return ContextualCarSerializer(annotation.substituteValue)
+        }
+        return ContextualCarSerializer()
+//        JsonMappingException: Can not write a field name, expecting a value (through reference chain: com.banjjoknim.playground.jackson.common.CarUsingContextualSerializerWithNoSecretAnnotation["secret"])
+//        return provider.findKeySerializer(property.type, property)
+    }
+}
+
 /**
  * AnnotationIntrospector 를 상속한 JacksonAnnotationIntrospector 은 Jackson 라이브러리가 직렬화/역직렬화시 `JacksonAnnotation` 정보를 어떻게 처리할지에 대한 정보가 정의되어 있는 클래스다.
  *

놀이터(예제 코드 작성)/jackson/src/test/kotlin/com/banjjoknim/playground/jackson/jsonserialize/CarSerializersTest.kt

@@ -1,7 +1,9 @@
 package com.banjjoknim.playground.jackson.jsonserialize
 
 import com.banjjoknim.playground.jackson.common.Car
-import com.banjjoknim.playground.jackson.common.CarUsingJsonSerializeAnnotation
+import com.banjjoknim.playground.jackson.common.CarUsingContextualSerializerWithNoSecretAnnotation
+import com.banjjoknim.playground.jackson.common.CarUsingContextualSerializerWithSecretAnnotation
+import com.banjjoknim.playground.jackson.common.CarUsingJsonSerializeAnnotationCarSerializer
 import com.banjjoknim.playground.jackson.common.CarUsingNoAnnotation
 import com.banjjoknim.playground.jackson.common.CarUsingSecretAnnotation
 import com.banjjoknim.playground.jackson.common.Owner
@@ -32,7 +34,11 @@ class CarSerializersTest {
         private val owner = Owner("ban", 30)
         private val car = Car("banjjoknim", 10_000_000, owner)
         private val carUsingNoAnnotation = CarUsingNoAnnotation()
-        private val carUsingJsonSerializeAnnotation = CarUsingJsonSerializeAnnotation()
+        private val carUsingJsonSerializeAnnotationCarSerializer = CarUsingJsonSerializeAnnotationCarSerializer()
+        private val carUsingContextualSerializerWithSecretAnnotation =
+            CarUsingContextualSerializerWithSecretAnnotation()
+        private val carUsingContextualSerializerWithNoSecretAnnotation =
+            CarUsingContextualSerializerWithNoSecretAnnotation()
         private val carUsingSecretAnnotation = CarUsingSecretAnnotation()
     }
 
@@ -141,12 +147,26 @@ class CarSerializersTest {
             // given
 
             // when
-            val actual = mapper.writeValueAsString(carUsingJsonSerializeAnnotation)
+            val actual = mapper.writeValueAsString(carUsingJsonSerializeAnnotationCarSerializer)
 
             // then
             assertThat(actual).isEqualTo("""{"name":"banjjoknim","secret":"****","price":10000000,"owner":{"name":"ban","age":30}}""")
         }
 
+        @Test
+        fun `ContextualSerializer 를 상속 받은 구현체를 이용해서 직렬화한다`() {
+            // given
+
+            // when
+            val actualWithSecretAnnotation = mapper.writeValueAsString(carUsingContextualSerializerWithSecretAnnotation)
+            val actualWithNoSecretAnnotation =
+                mapper.writeValueAsString(carUsingContextualSerializerWithNoSecretAnnotation)
+
+            // then
+            assertThat(actualWithSecretAnnotation).isEqualTo("""{"name":"banjjoknim","secret":"hello world!!","price":10000000,"owner":{"name":"ban","age":30}}""")
+            assertThat(actualWithNoSecretAnnotation).isEqualTo("""{"name":"banjjoknim","secret":"this is default value in ContextualCarSerializer","price":10000000,"owner":{"name":"ban","age":30}}""")
+        }
+
         @Test
         fun `@Secret 어노테이션, AnnotationIntrospector 을 적용하여 직렬화한다`() {
             // given
@@ -239,7 +259,10 @@ class CarSerializersTest {
 
             // when
             mapper.setAnnotationIntrospector(
-                AnnotationIntrospector.pair(SecretAnnotationIntrospector(), originalAnnotationIntrospector) // 내부 구현은 아래와 같다.
+                AnnotationIntrospector.pair(
+                    SecretAnnotationIntrospector(),
+                    originalAnnotationIntrospector
+                ) // 내부 구현은 아래와 같다.
 //                AnnotationIntrospectorPair(SecretAnnotationIntrospector(), originalAnnotationIntrospector)
             )
             val allIntrospectorNames = mapper.serializationConfig.annotationIntrospector.allIntrospectors()