use objectMapperForSerialization for kotlin type classes

src/main/resources/templates/kotlin-lang/type.ftl

@@ -88,7 +88,7 @@ open class ${className}()<#if implements?has_content> : <#list implements as int
     <#if field.type?ends_with("?")>
         if (${field.name} != null) {
         <#if toStringForRequest>
-            joiner.add("${field.originalName}: " + GraphQLRequestSerializer.getEntry(${field.name}))
+            joiner.add("${field.originalName}: " + GraphQLRequestSerializer.getEntry(${field.name}<#if field.serializeUsingObjectMapper>, true</#if>))
         <#else>
         <#if field.type == "String?">
             joiner.add("${field.originalName}: \"" + ${field.name} + "\"");
@@ -99,7 +99,7 @@ open class ${className}()<#if implements?has_content> : <#list implements as int
         }
     <#else>
         <#if toStringForRequest>
-        joiner.add("${field.originalName}: " + GraphQLRequestSerializer.getEntry(${field.name}))
+        joiner.add("${field.originalName}: " + GraphQLRequestSerializer.getEntry(${field.name}<#if field.serializeUsingObjectMapper>, true</#if>))
         <#else>
     <#if field.type == "String">
         joiner.add("${field.originalName}: \"" + ${field.name} + "\"");

src/test/java/com/kobylynskyi/graphql/codegen/kotlin/GraphQLCodegenCustomScalarMappingTest.java

@@ -90,4 +90,18 @@ void generate_UseObjectMapperToSerializeFields_Parameter() throws Exception {
                 new File("src/test/resources/expected-classes/kt/QueryINeedQueryRequest_custom_serializer.kt.txt"),
                 getFileByName(files, "QueryINeedQueryRequest.kt"));
     }
+
+    @Test
+    void generate_UseObjectMapperToSerializeFields_Type() throws Exception {
+        mappingConfig.putCustomTypeMappingIfAbsent("DateTime", "java.time.LocalDateTime");
+        mappingConfig.setUseObjectMapperForRequestSerialization(singleton("DateTime"));
+        new KotlinGraphQLCodegen(singletonList("src/test/resources/schemas/test.graphqls"),
+                outputBuildDir, mappingConfig, TestUtils.getStaticGeneratedInfo()).generate();
+
+        File[] files = Objects.requireNonNull(outputJavaClassesDir.listFiles());
+
+        assertSameTrimmedContent(new File("src/test/resources/expected-classes/kt/" +
+                        "Event_useObjectMapperForRequestSerialization.kt.txt"),
+                getFileByName(files, "Event.kt"));
+    }
 }

src/test/resources/expected-classes/kt/Event_useObjectMapperForRequestSerialization.kt.txt

@@ -0,0 +1,53 @@
+package com.kobylynskyi.graphql.test1
+
+import com.kobylynskyi.graphql.codegen.model.graphql.GraphQLRequestSerializer
+import java.util.StringJoiner
+
+/**
+ * An event that describes a thing that happens
+ */
+@javax.annotation.Generated(
+    value = ["com.kobylynskyi.graphql.codegen.GraphQLCodegen"],
+    date = "2020-12-31T23:59:59-0500"
+)
+data class Event(
+    val id: String?,
+    val categoryId: String?,
+    val properties: List<EventProperty?>?,
+    val status: EventStatus?,
+    val createdBy: String?,
+    val createdDateTime: java.time.LocalDateTime?,
+    val active: Boolean?,
+    val rating: Int?
+) {
+
+    // In the future, it maybe change.
+    override fun toString(): String {
+        val joiner = StringJoiner(", ", "{ ", " }")
+        if (id != null) {
+            joiner.add("id: " + GraphQLRequestSerializer.getEntry(id))
+        }
+        if (categoryId != null) {
+            joiner.add("categoryId: " + GraphQLRequestSerializer.getEntry(categoryId))
+        }
+        if (properties != null) {
+            joiner.add("properties: " + GraphQLRequestSerializer.getEntry(properties))
+        }
+        if (status != null) {
+            joiner.add("status: " + GraphQLRequestSerializer.getEntry(status))
+        }
+        if (createdBy != null) {
+            joiner.add("createdBy: " + GraphQLRequestSerializer.getEntry(createdBy))
+        }
+        if (createdDateTime != null) {
+            joiner.add("createdDateTime: " + GraphQLRequestSerializer.getEntry(createdDateTime, true))
+        }
+        if (active != null) {
+            joiner.add("active: " + GraphQLRequestSerializer.getEntry(active))
+        }
+        if (rating != null) {
+            joiner.add("rating: " + GraphQLRequestSerializer.getEntry(rating))
+        }
+        return joiner.toString()
+    }
+}

src/test/resources/expected-classes/kt/restricted-words/Super.kt.txt

@@ -32,7 +32,7 @@ data class Super(
             joiner.add("Int: " + GraphQLRequestSerializer.getEntry(Int))
         }
         if (date != null) {
-            joiner.add("date: " + GraphQLRequestSerializer.getEntry(date))
+            joiner.add("date: " + GraphQLRequestSerializer.getEntry(date, true))
         }
         return joiner.toString()
     }