feat : Car Serializer 추가

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

@@ -0,0 +1,3 @@
+package com.banjjoknim.playground.jsonserialize
+
+data class Car(val name: String, val price: Int = 0)

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

@@ -0,0 +1,38 @@
+package com.banjjoknim.playground.jsonserialize
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.SerializerProvider
+import com.fasterxml.jackson.databind.ser.std.StdSerializer
+
+/**
+ * [jackson-object-mapper-tutorial](https://www.baeldung.com/jackson-object-mapper-tutorial) 참고.
+ *
+ * Custom Serializer 를 만들기 위해서는 아래와 같이 StdSerializer<T> 를 상속해야 한다.
+ *
+ * @see com.fasterxml.jackson.databind.ser.std.StdSerializer
+ * @see com.fasterxml.jackson.databind.ser.ContextualSerializer
+ */
+class CarSerializer : StdSerializer<Car>(Car::class.java) {
+    override fun serialize(value: Car, gen: JsonGenerator, provider: SerializerProvider) {
+        gen.writeStartObject()
+        gen.writeStringField("name", value.name)
+        gen.writeNumberField("price", value.price)
+        gen.writeEndObject()
+    }
+}
+
+class CarNameSerializer : StdSerializer<Car>(Car::class.java) {
+    override fun serialize(value: Car, gen: JsonGenerator, provider: SerializerProvider) {
+        gen.writeStartObject()
+        gen.writeStringField("name", value.name)
+        gen.writeEndObject()
+    }
+}
+
+class CarPriceSerializer : StdSerializer<Car>(Car::class.java) {
+    override fun serialize(value: Car, gen: JsonGenerator, provider: SerializerProvider) {
+        gen.writeStartObject()
+        gen.writeNumberField("price", value.price)
+        gen.writeEndObject()
+    }
+}

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

@@ -0,0 +1,90 @@
+package com.banjjoknim.playground.jsonserialize
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.kotlin.registerKotlinModule
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+
+/**
+ * @see com.fasterxml.jackson.databind.ObjectMapper
+ * @see com.fasterxml.jackson.databind.module.SimpleModule
+ * @see com.fasterxml.jackson.databind.ser.DefaultSerializerProvider
+ * @see com.fasterxml.jackson.databind.ser.BeanSerializer -> 객체를 직렬화할때 사용되는 Serializer
+ * @see com.fasterxml.jackson.core.json.WriterBasedJsonGenerator
+ * @see com.fasterxml.jackson.databind.ser.std.BeanSerializerBase
+ * @see com.fasterxml.jackson.databind.ser.BeanPropertyWriter
+ */
+class CarSerializerTest {
+
+    private lateinit var mapper: ObjectMapper
+
+    companion object {
+        private val car = Car("banjjoknim", 10_000_000)
+    }
+
+    @BeforeEach
+    fun setup() {
+        mapper = ObjectMapper().registerKotlinModule()
+    }
+
+    @Test
+    fun `기본 ObjectMapper의 동작을 테스트한다`() {
+        // given
+
+        // when
+        val result = mapper.writeValueAsString(car)
+
+        // then
+        assertThat(result).isEqualTo("""{"name":"banjjoknim","price":10000000}""")
+    }
+
+    @DisplayName("등록된 커스텀 직렬화기의 동작을 테스트한다")
+    @Nested
+    inner class CarSerializerTestCases {
+        @Test
+        fun `모든 필드를 직렬화한다`() {
+            // given
+            val module = SimpleModule()
+            module.addSerializer(Car::class.java, CarSerializer())
+            mapper.registerModule(module)
+
+            // when
+            val result = mapper.writeValueAsString(car)
+
+            // then
+            assertThat(result).isEqualTo("""{"name":"banjjoknim","price":10000000}""")
+        }
+
+        @Test
+        fun `이름만 직렬화한다`() {
+            // given
+            val module = SimpleModule()
+            module.addSerializer(Car::class.java, CarNameSerializer())
+            mapper.registerModule(module)
+
+            // when
+            val result = mapper.writeValueAsString(car)
+
+            // then
+            assertThat(result).isEqualTo("""{"name":"banjjoknim"}""")
+        }
+
+        @Test
+        fun `가격만 직렬화한다`() {
+            // given
+            val module = SimpleModule()
+            module.addSerializer(Car::class.java, CarPriceSerializer())
+            mapper.registerModule(module)
+
+            // when
+            val result = mapper.writeValueAsString(car)
+
+            // then
+            assertThat(result).isEqualTo("""{"price":10000000}""")
+        }
+    }
+}