diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinServerCodegen.java
index 2fc9871b9f59..5f5601968e98 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinServerCodegen.java
@@ -225,6 +225,11 @@ public void processOpts() {
             LOGGER.info("`library` option is empty. Default to {}", DEFAULT_LIBRARY);
         }
 
+        if (isKtor()) {
+            typeMapping.put("date-time", "kotlin.String");
+            typeMapping.put("DateTime", "kotlin.String");
+        }
+
         if (additionalProperties.containsKey(Constants.AUTOMATIC_HEAD_REQUESTS)) {
             setAutoHeadFeatureEnabled(convertPropertyToBooleanAndWriteBack(Constants.AUTOMATIC_HEAD_REQUESTS));
         } else {
@@ -353,6 +358,7 @@ public static class Constants {
         public static final String USE_MUTINY_DESC = "Whether to use Mutiny (should not be used with useCoroutines). This option is currently supported only when using jaxrs-spec library.";
         public static final String OMIT_GRADLE_WRAPPER = "omitGradleWrapper";
         public static final String OMIT_GRADLE_WRAPPER_DESC = "Whether to omit Gradle wrapper for creating a sub project.";
+        public static final String KOTLIN_SERIALIZATION = "kotlinSerialization";
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/data_class.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/data_class.mustache
index ea72ac7c116d..0f8615de28d9 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/data_class.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/data_class.mustache
@@ -1,35 +1,21 @@
-{{#parcelizeModels}}
-import android.os.Parcelable
-import kotlinx.parcelize.Parcelize
-
-{{/parcelizeModels}}
-{{#serializableModel}}
-import java.io.Serializable
-{{/serializableModel}}
+import kotlinx.serialization.Serializable
 /**
  * {{{description}}}
 {{#vars}}
  * @param {{{name}}} {{{description}}}
 {{/vars}}
  */
-{{#parcelizeModels}}
-@Parcelize
-{{/parcelizeModels}}
+@Serializable
 {{#hasVars}}data {{/hasVars}}class {{classname}}(
 {{#requiredVars}}
 {{>data_class_req_var}}{{^-last}},
 {{/-last}}{{/requiredVars}}{{#hasRequired}}{{#hasOptional}},
 {{/hasOptional}}{{/hasRequired}}{{#optionalVars}}{{>data_class_opt_var}}{{^-last}},
 {{/-last}}{{/optionalVars}}
-) {{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}{{^parcelizeModels}}{{#serializableModel}}: Serializable {{/serializableModel}}{{/parcelizeModels}}{{#parcelizeModels}}{{#serializableModel}} : Parcelable, Serializable {{/serializableModel}}{{/parcelizeModels}}
+)
 {{#vendorExtensions.x-has-data-class-body}}
 {
 {{/vendorExtensions.x-has-data-class-body}}
-{{#serializableModel}}
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
-{{/serializableModel}}
 {{#hasEnums}}
     {{#vars}}
     {{#isEnum}}
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/ApiKeyAuth.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/ApiKeyAuth.kt.mustache
index c2cad7fe7a7f..542744384a71 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/ApiKeyAuth.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/ApiKeyAuth.kt.mustache
@@ -1,4 +1,4 @@
-package org.openapitools.server.infrastructure
+package {{packageName}}.infrastructure
 
 import io.ktor.http.auth.*
 import io.ktor.server.application.*
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/AppMain.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/AppMain.kt.mustache
index 5ba3775c92cf..870ec720e139 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/AppMain.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/AppMain.kt.mustache
@@ -1,7 +1,6 @@
 package {{packageName}}
 
 import io.ktor.server.application.*
-import io.ktor.serialization.gson.*
 import io.ktor.http.*
 {{#featureResources}}
 import io.ktor.server.resources.*
@@ -30,24 +29,19 @@ import java.util.concurrent.TimeUnit
 {{/featureMetrics}}
 import io.ktor.server.routing.*
 {{#hasAuthMethods}}
+{{#kotlinSerialization}}
+import io.ktor.serialization.kotlinx.json.json
+{{/kotlinSerialization}}
 import com.typesafe.config.ConfigFactory
 import io.ktor.client.HttpClient
 import io.ktor.client.engine.apache.Apache
 import io.ktor.server.config.HoconApplicationConfig
 import io.ktor.server.auth.*
-import org.openapitools.server.infrastructure.*
+import {{packageName}}.infrastructure.*
 {{/hasAuthMethods}}
 {{#generateApis}}{{#apiInfo}}{{#apis}}import {{apiPackage}}.{{classname}}
 {{/apis}}{{/apiInfo}}{{/generateApis}}
 
-{{#hasAuthMethods}}
-internal val settings = HoconApplicationConfig(ConfigFactory.defaultApplication(HTTP::class.java.classLoader))
-
-object HTTP {
-    val client = HttpClient(Apache)
-}
-{{/hasAuthMethods}}
-
 fun Application.main() {
     install(DefaultHeaders)
     {{#featureMetrics}}
@@ -62,7 +56,9 @@ fun Application.main() {
     {{/featureMetrics}}
 {{#generateApis}}
     install(ContentNegotiation) {
-        register(ContentType.Application.Json, GsonConverter())
+    {{#kotlinSerialization}}
+        json()
+    {{/kotlinSerialization}}
     }
     {{#featureAutoHead}}
     install(AutoHeadResponse) // see https://ktor.io/docs/autoheadresponse.html
@@ -125,7 +121,7 @@ fun Application.main() {
     {{/authMethods}}
     }
     {{/hasAuthMethods}}
-    install(Routing) {
+    routing {
     {{#apiInfo}}
     {{#apis}}
     {{#operations}}
@@ -134,6 +130,5 @@ fun Application.main() {
     {{/apis}}
     {{/apiInfo}}
     }
-
 {{/generateApis}}
 }
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/Paths.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/Paths.kt.mustache
index a575ea678772..48c8a7e49d88 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/Paths.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/Paths.kt.mustache
@@ -18,10 +18,10 @@ object Paths {
      {{#allParams}}* @param {{paramName}} {{description}} {{^required}}(optional{{#defaultValue}}, default to {{{.}}}{{/defaultValue}}){{/required}}
      {{/allParams}}*/
     {{#hasParams}}
-    @Serializable @Resource("{{{path}}}") class {{operationId}}({{#allParams}}val {{paramName}}: {{{dataType}}}{{^required}}? = null{{/required}}{{#required}}{{#isNullable}}?{{/isNullable}}{{/required}}{{^-last}}, {{/-last}}{{/allParams}})
+    @Resource("{{{path}}}") class {{operationId}}({{#pathParams}}val {{paramName}}: {{{dataType}}}{{^required}}? = null{{/required}}{{#required}}{{#isNullable}}?{{/isNullable}}{{/required}}{{^-last}}, {{/-last}}{{/pathParams}})
     {{/hasParams}}
     {{^hasParams}}
-    @Serializable @Resource("{{{path}}}") class {{operationId}}
+    @Resource("{{{path}}}") class {{operationId}}
     {{/hasParams}}
 
     {{/operation}}
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_principal.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_principal.mustache
index 17c32a4c40a2..ad01dd85aa75 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_principal.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_principal.mustache
@@ -1,10 +1,10 @@
 {{#authMethods}}
 {{#isBasicBasic}}
-val principal = call.authentication.principal<UserIdPrincipal>()!!
+val principal = call.authentication.principal<UserIdPrincipal>()
 {{/isBasicBasic}}{{^isBasicBasic}}{{#isApiKey}}
-val principal = call.authentication.principal<ApiPrincipal>()!!
+val principal = call.authentication.principal<ApiPrincipal>()
 {{/isApiKey}}{{^isApiKey}}{{#isOAuth}}
-val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+val principal = call.authentication.principal<OAuthAccessTokenResponse>()
 {{/isOAuth}}{{^isOAuth}}
 val principal = null!!
 {{/isOAuth}}{{/isApiKey}}{{/isBasicBasic}}
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_response.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_response.mustache
index 931dad98f5e1..323f266e8256 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_response.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/_response.mustache
@@ -2,7 +2,7 @@ val exampleContentType = "{{{contentType}}}"
 val exampleContentString = """{{&example}}"""
 
 when (exampleContentType) {
-    "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+    "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
     "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
     else -> call.respondText(exampleContentString)
 }
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/api.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/api.mustache
index eb1da3bd527d..885ba6ae50dc 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/api.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/api.mustache
@@ -1,7 +1,6 @@
 {{>licenseInfo}}
 package {{apiPackage}}
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -23,7 +22,6 @@ import {{packageName}}.infrastructure.ApiPrincipal
 
 {{#operations}}
 fun Route.{{classname}}() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
 {{#operation}}
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/build.gradle.kts.mustache b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/build.gradle.kts.mustache
index 3dc3dd38f043..268c54c5093a 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/build.gradle.kts.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/build.gradle.kts.mustache
@@ -7,7 +7,8 @@ version = "{{artifactVersion}}"
 
 plugins {
     kotlin("jvm") version "2.0.20"
-    id("io.ktor.plugin") version "2.3.12"
+    id("io.ktor.plugin") version "3.0.2"
+    kotlin("plugin.serialization") version "2.0.20"
 }
 
 application {
@@ -35,7 +36,7 @@ dependencies {
 {{/featureAutoHead}}
     implementation("io.ktor:ktor-server-default-headers")
     implementation("io.ktor:ktor-server-content-negotiation")
-    implementation("io.ktor:ktor-serialization-gson")
+    implementation("io.ktor:ktor-serialization-kotlinx-json")
 {{#featureResources}}
     implementation("io.ktor:ktor-server-resources")
 {{/featureResources}}
diff --git a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/gradle.properties b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/gradle.properties
index d507b58c1c87..fb877a9edd28 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/gradle.properties
+++ b/modules/openapi-generator/src/main/resources/kotlin-server/libraries/ktor/gradle.properties
@@ -1,4 +1,4 @@
 kotlin.code.style=official
-ktor_version=2.3.12
+ktor_version=3.0.2
 kotlin_version=2.0.20
 logback_version=1.4.14
\ No newline at end of file
diff --git a/samples/server/petstore/kotlin-server-modelMutable/build.gradle.kts b/samples/server/petstore/kotlin-server-modelMutable/build.gradle.kts
index fb35b77164a8..ac3166e2f3a2 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/build.gradle.kts
+++ b/samples/server/petstore/kotlin-server-modelMutable/build.gradle.kts
@@ -7,7 +7,8 @@ version = "1.0.0"
 
 plugins {
     kotlin("jvm") version "2.0.20"
-    id("io.ktor.plugin") version "2.3.12"
+    id("io.ktor.plugin") version "3.0.2"
+    kotlin("plugin.serialization") version "2.0.20"
 }
 
 application {
@@ -29,7 +30,7 @@ dependencies {
     implementation("io.ktor:ktor-server-auto-head-response")
     implementation("io.ktor:ktor-server-default-headers")
     implementation("io.ktor:ktor-server-content-negotiation")
-    implementation("io.ktor:ktor-serialization-gson")
+    implementation("io.ktor:ktor-serialization-kotlinx-json")
     implementation("io.ktor:ktor-server-resources")
     implementation("io.ktor:ktor-server-hsts")
     implementation("io.ktor:ktor-server-compression")
diff --git a/samples/server/petstore/kotlin-server-modelMutable/gradle.properties b/samples/server/petstore/kotlin-server-modelMutable/gradle.properties
index d507b58c1c87..fb877a9edd28 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/gradle.properties
+++ b/samples/server/petstore/kotlin-server-modelMutable/gradle.properties
@@ -1,4 +1,4 @@
 kotlin.code.style=official
-ktor_version=2.3.12
+ktor_version=3.0.2
 kotlin_version=2.0.20
 logback_version=1.4.14
\ No newline at end of file
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/AppMain.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/AppMain.kt
index 2de9d58ce937..5ea257e8c473 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/AppMain.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/AppMain.kt
@@ -1,7 +1,6 @@
 package org.openapitools.server
 
 import io.ktor.server.application.*
-import io.ktor.serialization.gson.*
 import io.ktor.http.*
 import io.ktor.server.resources.*
 import io.ktor.server.plugins.autohead.*
@@ -24,12 +23,6 @@ import org.openapitools.server.apis.StoreApi
 import org.openapitools.server.apis.UserApi
 
 
-internal val settings = HoconApplicationConfig(ConfigFactory.defaultApplication(HTTP::class.java.classLoader))
-
-object HTTP {
-    val client = HttpClient(Apache)
-}
-
 fun Application.main() {
     install(DefaultHeaders)
     install(DropwizardMetrics) {
@@ -41,7 +34,6 @@ fun Application.main() {
         reporter.start(10, TimeUnit.SECONDS)
     }
     install(ContentNegotiation) {
-        register(ContentType.Application.Json, GsonConverter())
     }
     install(AutoHeadResponse) // see https://ktor.io/docs/autoheadresponse.html
     install(Compression, ApplicationCompressionConfiguration()) // see https://ktor.io/docs/compression.html
@@ -66,10 +58,9 @@ fun Application.main() {
             }
         }
     }
-    install(Routing) {
+    routing {
         PetApi()
         StoreApi()
         UserApi()
     }
-
 }
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/Paths.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/Paths.kt
index effea4faa7aa..96b4afcaa488 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/Paths.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/Paths.kt
@@ -21,7 +21,7 @@ object Paths {
      * 
      * @param body Pet object that needs to be added to the store 
      */
-    @Serializable @Resource("/pet") class addPet(val body: Pet)
+    @Resource("/pet") class addPet()
 
     /**
      * Deletes a pet
@@ -29,35 +29,35 @@ object Paths {
      * @param petId Pet id to delete 
      * @param apiKey  (optional)
      */
-    @Serializable @Resource("/pet/{petId}") class deletePet(val petId: kotlin.Long, val apiKey: kotlin.String? = null)
+    @Resource("/pet/{petId}") class deletePet(val petId: kotlin.Long)
 
     /**
      * Finds Pets by status
      * Multiple status values can be provided with comma separated strings
      * @param status Status values that need to be considered for filter 
      */
-    @Serializable @Resource("/pet/findByStatus") class findPetsByStatus(val status: kotlin.collections.MutableList<kotlin.String>)
+    @Resource("/pet/findByStatus") class findPetsByStatus()
 
     /**
      * Finds Pets by tags
      * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
      * @param tags Tags to filter by 
      */
-    @Serializable @Resource("/pet/findByTags") class findPetsByTags(val tags: kotlin.collections.MutableList<kotlin.String>)
+    @Resource("/pet/findByTags") class findPetsByTags()
 
     /**
      * Find pet by ID
      * Returns a single pet
      * @param petId ID of pet to return 
      */
-    @Serializable @Resource("/pet/{petId}") class getPetById(val petId: kotlin.Long)
+    @Resource("/pet/{petId}") class getPetById(val petId: kotlin.Long)
 
     /**
      * Update an existing pet
      * 
      * @param body Pet object that needs to be added to the store 
      */
-    @Serializable @Resource("/pet") class updatePet(val body: Pet)
+    @Resource("/pet") class updatePet()
 
     /**
      * Updates a pet in the store with form data
@@ -66,7 +66,7 @@ object Paths {
      * @param name Updated name of the pet (optional)
      * @param status Updated status of the pet (optional)
      */
-    @Serializable @Resource("/pet/{petId}") class updatePetWithForm(val petId: kotlin.Long, val name: kotlin.String? = null, val status: kotlin.String? = null)
+    @Resource("/pet/{petId}") class updatePetWithForm(val petId: kotlin.Long)
 
     /**
      * uploads an image
@@ -75,69 +75,69 @@ object Paths {
      * @param additionalMetadata Additional data to pass to server (optional)
      * @param file file to upload (optional)
      */
-    @Serializable @Resource("/pet/{petId}/uploadImage") class uploadFile(val petId: kotlin.Long, val additionalMetadata: kotlin.String? = null, val file: java.io.File? = null)
+    @Resource("/pet/{petId}/uploadImage") class uploadFile(val petId: kotlin.Long)
 
     /**
      * Delete purchase order by ID
      * For valid response try integer IDs with value &lt; 1000. Anything above 1000 or nonintegers will generate API errors
      * @param orderId ID of the order that needs to be deleted 
      */
-    @Serializable @Resource("/store/order/{orderId}") class deleteOrder(val orderId: kotlin.String)
+    @Resource("/store/order/{orderId}") class deleteOrder(val orderId: kotlin.String)
 
     /**
      * Returns pet inventories by status
      * Returns a map of status codes to quantities
      */
-    @Serializable @Resource("/store/inventory") class getInventory
+    @Resource("/store/inventory") class getInventory
 
     /**
      * Find purchase order by ID
      * For valid response try integer IDs with value &lt;&#x3D; 5 or &gt; 10. Other values will generate exceptions
      * @param orderId ID of pet that needs to be fetched 
      */
-    @Serializable @Resource("/store/order/{orderId}") class getOrderById(val orderId: kotlin.Long)
+    @Resource("/store/order/{orderId}") class getOrderById(val orderId: kotlin.Long)
 
     /**
      * Place an order for a pet
      * 
      * @param body order placed for purchasing the pet 
      */
-    @Serializable @Resource("/store/order") class placeOrder(val body: Order)
+    @Resource("/store/order") class placeOrder()
 
     /**
      * Create user
      * This can only be done by the logged in user.
      * @param body Created user object 
      */
-    @Serializable @Resource("/user") class createUser(val body: User)
+    @Resource("/user") class createUser()
 
     /**
      * Creates list of users with given input array
      * 
      * @param body List of user object 
      */
-    @Serializable @Resource("/user/createWithArray") class createUsersWithArrayInput(val body: kotlin.collections.MutableList<User>)
+    @Resource("/user/createWithArray") class createUsersWithArrayInput()
 
     /**
      * Creates list of users with given input array
      * 
      * @param body List of user object 
      */
-    @Serializable @Resource("/user/createWithList") class createUsersWithListInput(val body: kotlin.collections.MutableList<User>)
+    @Resource("/user/createWithList") class createUsersWithListInput()
 
     /**
      * Delete user
      * This can only be done by the logged in user.
      * @param username The name that needs to be deleted 
      */
-    @Serializable @Resource("/user/{username}") class deleteUser(val username: kotlin.String)
+    @Resource("/user/{username}") class deleteUser(val username: kotlin.String)
 
     /**
      * Get user by user name
      * 
      * @param username The name that needs to be fetched. Use user1 for testing. 
      */
-    @Serializable @Resource("/user/{username}") class getUserByName(val username: kotlin.String)
+    @Resource("/user/{username}") class getUserByName(val username: kotlin.String)
 
     /**
      * Logs user into the system
@@ -145,13 +145,13 @@ object Paths {
      * @param username The user name for login 
      * @param password The password for login in clear text 
      */
-    @Serializable @Resource("/user/login") class loginUser(val username: kotlin.String, val password: kotlin.String)
+    @Resource("/user/login") class loginUser()
 
     /**
      * Logs out current logged in user session
      * 
      */
-    @Serializable @Resource("/user/logout") class logoutUser
+    @Resource("/user/logout") class logoutUser
 
     /**
      * Updated user
@@ -159,6 +159,6 @@ object Paths {
      * @param username name that need to be deleted 
      * @param body Updated user object 
      */
-    @Serializable @Resource("/user/{username}") class updateUser(val username: kotlin.String, val body: User)
+    @Resource("/user/{username}") class updateUser(val username: kotlin.String)
 
 }
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/PetApi.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
index d95a4b4d0883..b72ec0d72cec 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -30,13 +29,12 @@ import org.openapitools.server.models.ModelApiResponse
 import org.openapitools.server.models.Pet
 
 fun Route.PetApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     authenticate("petstore_auth") {
     post<Paths.addPet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -47,7 +45,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     delete<Paths.deletePet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -58,7 +56,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     get<Paths.findPetsByStatus> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -97,7 +95,7 @@ fun Route.PetApi() {
             } ]"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -108,7 +106,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     get<Paths.findPetsByTags> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -147,7 +145,7 @@ fun Route.PetApi() {
             } ]"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -158,7 +156,7 @@ fun Route.PetApi() {
     authenticate("api_key") {
     get<Paths.getPetById> {
         
-        val principal = call.authentication.principal<ApiPrincipal>()!!
+        val principal = call.authentication.principal<ApiPrincipal>()
         
         
         val exampleContentType = "application/json"
@@ -181,7 +179,7 @@ fun Route.PetApi() {
             }"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -192,7 +190,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     put<Paths.updatePet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -203,7 +201,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     post<Paths.updatePetWithForm> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -214,7 +212,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     post<Paths.uploadFile> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -225,7 +223,7 @@ fun Route.PetApi() {
             }"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
index fe780f7feb46..4a4395778401 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -29,7 +28,6 @@ import org.openapitools.server.infrastructure.ApiPrincipal
 import org.openapitools.server.models.Order
 
 fun Route.StoreApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     delete<Paths.deleteOrder> {
@@ -40,7 +38,7 @@ fun Route.StoreApi() {
     authenticate("api_key") {
     get<Paths.getInventory> {
         
-        val principal = call.authentication.principal<ApiPrincipal>()!!
+        val principal = call.authentication.principal<ApiPrincipal>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -60,7 +58,7 @@ fun Route.StoreApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
@@ -79,7 +77,7 @@ fun Route.StoreApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/UserApi.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
index ccf0509fca2e..299f743e141d 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -29,7 +28,6 @@ import org.openapitools.server.infrastructure.ApiPrincipal
 import org.openapitools.server.models.User
 
 fun Route.UserApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     post<Paths.createUser> {
@@ -66,7 +64,7 @@ fun Route.UserApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Category.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Category.kt
index 949cf3a7a5a0..82813cdbff3e 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Category.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Category.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Category(
     var id: kotlin.Long? = null,
     var name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
index 7a0ac1f246df..dcc1ed13510b 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
@@ -12,15 +12,17 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * Describes the result of uploading an image resource
  * @param code 
  * @param type 
  * @param message 
  */
+@Serializable
 data class ModelApiResponse(
     var code: kotlin.Int? = null,
     var type: kotlin.String? = null,
     var message: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Order.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Order.kt
index c691b645c43d..d5a9b56748f7 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Order.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Order.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * An order for a pets from the pet store
  * @param id 
@@ -21,15 +22,16 @@ package org.openapitools.server.models
  * @param status Order Status
  * @param complete 
  */
+@Serializable
 data class Order(
     var id: kotlin.Long? = null,
     var petId: kotlin.Long? = null,
     var quantity: kotlin.Int? = null,
-    var shipDate: java.time.OffsetDateTime? = null,
+    var shipDate: kotlin.String? = null,
     /* Order Status */
     var status: Order.Status? = null,
     var complete: kotlin.Boolean? = false
-) 
+)
 {
     /**
     * Order Status
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Pet.kt
index e12a818c1b57..e9095e0a7c60 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -14,6 +14,7 @@ package org.openapitools.server.models
 import org.openapitools.server.models.Category
 import org.openapitools.server.models.Tag
 
+import kotlinx.serialization.Serializable
 /**
  * A pet for sale in the pet store
  * @param name 
@@ -23,6 +24,7 @@ import org.openapitools.server.models.Tag
  * @param tags 
  * @param status pet status in the store
  */
+@Serializable
 data class Pet(
     var name: kotlin.String,
     var photoUrls: kotlin.collections.MutableList<kotlin.String>,
@@ -31,7 +33,7 @@ data class Pet(
     var tags: kotlin.collections.MutableList<Tag>? = null,
     /* pet status in the store */
     var status: Pet.Status? = null
-) 
+)
 {
     /**
     * pet status in the store
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Tag.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Tag.kt
index 99e770cd7b9f..26a16d0acc37 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Tag.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/Tag.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Tag(
     var id: kotlin.Long? = null,
     var name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/User.kt b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/User.kt
index e63e2596d4bf..57f4e607386a 100644
--- a/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/User.kt
+++ b/samples/server/petstore/kotlin-server-modelMutable/src/main/kotlin/org/openapitools/server/models/User.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -23,6 +24,7 @@ package org.openapitools.server.models
  * @param phone 
  * @param userStatus User Status
  */
+@Serializable
 data class User(
     var id: kotlin.Long? = null,
     var username: kotlin.String? = null,
@@ -33,5 +35,5 @@ data class User(
     var phone: kotlin.String? = null,
     /* User Status */
     var userStatus: kotlin.Int? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server-required-and-nullable-properties/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server-required-and-nullable-properties/src/main/kotlin/org/openapitools/server/models/Pet.kt
index 8dddb90062b1..5266d4aaa2f1 100644
--- a/samples/server/petstore/kotlin-server-required-and-nullable-properties/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server-required-and-nullable-properties/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * 
  * @param notNullableRequired 
@@ -19,10 +20,11 @@ package org.openapitools.server.models
  * @param nullableNotRequired 
  * @param notNullableNotRequired 
  */
+@Serializable
 data class Pet(
     val notNullableRequired: kotlin.String,
     val nullableRequired: kotlin.String?,
     val nullableNotRequired: kotlin.String? = null,
     val notNullableNotRequired: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Category.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Category.kt
index 71098339bc80..0c3ccfcfe850 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Category.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Category.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Category(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
index 9e80c50c6604..5ecc51991934 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
@@ -12,15 +12,17 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * Describes the result of uploading an image resource
  * @param code 
  * @param type 
  * @param message 
  */
+@Serializable
 data class ModelApiResponse(
     val code: kotlin.Int? = null,
     val type: kotlin.String? = null,
     val message: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Order.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Order.kt
index be802beb8d80..d015eb6b780a 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Order.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Order.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * An order for a pets from the pet store
  * @param id 
@@ -21,6 +22,7 @@ package org.openapitools.server.models
  * @param status Order Status
  * @param complete 
  */
+@Serializable
 data class Order(
     val id: kotlin.Long? = null,
     val petId: kotlin.Long? = null,
@@ -29,7 +31,7 @@ data class Order(
     /* Order Status */
     val status: Order.Status? = null,
     val complete: kotlin.Boolean? = false
-) 
+)
 {
     /**
     * Order Status
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Pet.kt
index e5723fedd633..929d729b09bb 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -14,6 +14,7 @@ package org.openapitools.server.models
 import org.openapitools.server.models.Category
 import org.openapitools.server.models.Tag
 
+import kotlinx.serialization.Serializable
 /**
  * A pet for sale in the pet store
  * @param name 
@@ -23,6 +24,7 @@ import org.openapitools.server.models.Tag
  * @param tags 
  * @param status pet status in the store
  */
+@Serializable
 data class Pet(
     val name: kotlin.String,
     val photoUrls: kotlin.collections.List<kotlin.String>,
@@ -31,7 +33,7 @@ data class Pet(
     val tags: kotlin.collections.List<Tag>? = null,
     /* pet status in the store */
     val status: Pet.Status? = null
-) 
+)
 {
     /**
     * pet status in the store
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Tag.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Tag.kt
index 0a975290485e..76749aca3f4d 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Tag.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/Tag.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Tag(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/User.kt b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/User.kt
index a4742582f463..26757f921f43 100644
--- a/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/User.kt
+++ b/samples/server/petstore/kotlin-server/javalin-6/src/main/kotlin/org/openapitools/server/models/User.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -23,6 +24,7 @@ package org.openapitools.server.models
  * @param phone 
  * @param userStatus User Status
  */
+@Serializable
 data class User(
     val id: kotlin.Long? = null,
     val username: kotlin.String? = null,
@@ -33,5 +35,5 @@ data class User(
     val phone: kotlin.String? = null,
     /* User Status */
     val userStatus: kotlin.Int? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Category.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Category.kt
index 71098339bc80..0c3ccfcfe850 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Category.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Category.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Category(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
index 9e80c50c6604..5ecc51991934 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
@@ -12,15 +12,17 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * Describes the result of uploading an image resource
  * @param code 
  * @param type 
  * @param message 
  */
+@Serializable
 data class ModelApiResponse(
     val code: kotlin.Int? = null,
     val type: kotlin.String? = null,
     val message: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Order.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Order.kt
index be802beb8d80..d015eb6b780a 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Order.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Order.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * An order for a pets from the pet store
  * @param id 
@@ -21,6 +22,7 @@ package org.openapitools.server.models
  * @param status Order Status
  * @param complete 
  */
+@Serializable
 data class Order(
     val id: kotlin.Long? = null,
     val petId: kotlin.Long? = null,
@@ -29,7 +31,7 @@ data class Order(
     /* Order Status */
     val status: Order.Status? = null,
     val complete: kotlin.Boolean? = false
-) 
+)
 {
     /**
     * Order Status
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Pet.kt
index e5723fedd633..929d729b09bb 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -14,6 +14,7 @@ package org.openapitools.server.models
 import org.openapitools.server.models.Category
 import org.openapitools.server.models.Tag
 
+import kotlinx.serialization.Serializable
 /**
  * A pet for sale in the pet store
  * @param name 
@@ -23,6 +24,7 @@ import org.openapitools.server.models.Tag
  * @param tags 
  * @param status pet status in the store
  */
+@Serializable
 data class Pet(
     val name: kotlin.String,
     val photoUrls: kotlin.collections.List<kotlin.String>,
@@ -31,7 +33,7 @@ data class Pet(
     val tags: kotlin.collections.List<Tag>? = null,
     /* pet status in the store */
     val status: Pet.Status? = null
-) 
+)
 {
     /**
     * pet status in the store
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Tag.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Tag.kt
index 0a975290485e..76749aca3f4d 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Tag.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/Tag.kt
@@ -12,13 +12,15 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Tag(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/User.kt b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/User.kt
index a4742582f463..26757f921f43 100644
--- a/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/User.kt
+++ b/samples/server/petstore/kotlin-server/javalin/src/main/kotlin/org/openapitools/server/models/User.kt
@@ -12,6 +12,7 @@
 package org.openapitools.server.models
 
 
+import kotlinx.serialization.Serializable
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -23,6 +24,7 @@ package org.openapitools.server.models
  * @param phone 
  * @param userStatus User Status
  */
+@Serializable
 data class User(
     val id: kotlin.Long? = null,
     val username: kotlin.String? = null,
@@ -33,5 +35,5 @@ data class User(
     val phone: kotlin.String? = null,
     /* User Status */
     val userStatus: kotlin.Int? = null
-) 
+)
 
diff --git a/samples/server/petstore/kotlin-server/ktor/build.gradle.kts b/samples/server/petstore/kotlin-server/ktor/build.gradle.kts
index fb35b77164a8..ac3166e2f3a2 100644
--- a/samples/server/petstore/kotlin-server/ktor/build.gradle.kts
+++ b/samples/server/petstore/kotlin-server/ktor/build.gradle.kts
@@ -7,7 +7,8 @@ version = "1.0.0"
 
 plugins {
     kotlin("jvm") version "2.0.20"
-    id("io.ktor.plugin") version "2.3.12"
+    id("io.ktor.plugin") version "3.0.2"
+    kotlin("plugin.serialization") version "2.0.20"
 }
 
 application {
@@ -29,7 +30,7 @@ dependencies {
     implementation("io.ktor:ktor-server-auto-head-response")
     implementation("io.ktor:ktor-server-default-headers")
     implementation("io.ktor:ktor-server-content-negotiation")
-    implementation("io.ktor:ktor-serialization-gson")
+    implementation("io.ktor:ktor-serialization-kotlinx-json")
     implementation("io.ktor:ktor-server-resources")
     implementation("io.ktor:ktor-server-hsts")
     implementation("io.ktor:ktor-server-compression")
diff --git a/samples/server/petstore/kotlin-server/ktor/gradle.properties b/samples/server/petstore/kotlin-server/ktor/gradle.properties
index d507b58c1c87..fb877a9edd28 100644
--- a/samples/server/petstore/kotlin-server/ktor/gradle.properties
+++ b/samples/server/petstore/kotlin-server/ktor/gradle.properties
@@ -1,4 +1,4 @@
 kotlin.code.style=official
-ktor_version=2.3.12
+ktor_version=3.0.2
 kotlin_version=2.0.20
 logback_version=1.4.14
\ No newline at end of file
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/AppMain.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/AppMain.kt
index 2de9d58ce937..5ea257e8c473 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/AppMain.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/AppMain.kt
@@ -1,7 +1,6 @@
 package org.openapitools.server
 
 import io.ktor.server.application.*
-import io.ktor.serialization.gson.*
 import io.ktor.http.*
 import io.ktor.server.resources.*
 import io.ktor.server.plugins.autohead.*
@@ -24,12 +23,6 @@ import org.openapitools.server.apis.StoreApi
 import org.openapitools.server.apis.UserApi
 
 
-internal val settings = HoconApplicationConfig(ConfigFactory.defaultApplication(HTTP::class.java.classLoader))
-
-object HTTP {
-    val client = HttpClient(Apache)
-}
-
 fun Application.main() {
     install(DefaultHeaders)
     install(DropwizardMetrics) {
@@ -41,7 +34,6 @@ fun Application.main() {
         reporter.start(10, TimeUnit.SECONDS)
     }
     install(ContentNegotiation) {
-        register(ContentType.Application.Json, GsonConverter())
     }
     install(AutoHeadResponse) // see https://ktor.io/docs/autoheadresponse.html
     install(Compression, ApplicationCompressionConfiguration()) // see https://ktor.io/docs/compression.html
@@ -66,10 +58,9 @@ fun Application.main() {
             }
         }
     }
-    install(Routing) {
+    routing {
         PetApi()
         StoreApi()
         UserApi()
     }
-
 }
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/Paths.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/Paths.kt
index 4a9c3bb01944..96b4afcaa488 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/Paths.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/Paths.kt
@@ -21,7 +21,7 @@ object Paths {
      * 
      * @param body Pet object that needs to be added to the store 
      */
-    @Serializable @Resource("/pet") class addPet(val body: Pet)
+    @Resource("/pet") class addPet()
 
     /**
      * Deletes a pet
@@ -29,35 +29,35 @@ object Paths {
      * @param petId Pet id to delete 
      * @param apiKey  (optional)
      */
-    @Serializable @Resource("/pet/{petId}") class deletePet(val petId: kotlin.Long, val apiKey: kotlin.String? = null)
+    @Resource("/pet/{petId}") class deletePet(val petId: kotlin.Long)
 
     /**
      * Finds Pets by status
      * Multiple status values can be provided with comma separated strings
      * @param status Status values that need to be considered for filter 
      */
-    @Serializable @Resource("/pet/findByStatus") class findPetsByStatus(val status: kotlin.collections.List<kotlin.String>)
+    @Resource("/pet/findByStatus") class findPetsByStatus()
 
     /**
      * Finds Pets by tags
      * Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
      * @param tags Tags to filter by 
      */
-    @Serializable @Resource("/pet/findByTags") class findPetsByTags(val tags: kotlin.collections.List<kotlin.String>)
+    @Resource("/pet/findByTags") class findPetsByTags()
 
     /**
      * Find pet by ID
      * Returns a single pet
      * @param petId ID of pet to return 
      */
-    @Serializable @Resource("/pet/{petId}") class getPetById(val petId: kotlin.Long)
+    @Resource("/pet/{petId}") class getPetById(val petId: kotlin.Long)
 
     /**
      * Update an existing pet
      * 
      * @param body Pet object that needs to be added to the store 
      */
-    @Serializable @Resource("/pet") class updatePet(val body: Pet)
+    @Resource("/pet") class updatePet()
 
     /**
      * Updates a pet in the store with form data
@@ -66,7 +66,7 @@ object Paths {
      * @param name Updated name of the pet (optional)
      * @param status Updated status of the pet (optional)
      */
-    @Serializable @Resource("/pet/{petId}") class updatePetWithForm(val petId: kotlin.Long, val name: kotlin.String? = null, val status: kotlin.String? = null)
+    @Resource("/pet/{petId}") class updatePetWithForm(val petId: kotlin.Long)
 
     /**
      * uploads an image
@@ -75,69 +75,69 @@ object Paths {
      * @param additionalMetadata Additional data to pass to server (optional)
      * @param file file to upload (optional)
      */
-    @Serializable @Resource("/pet/{petId}/uploadImage") class uploadFile(val petId: kotlin.Long, val additionalMetadata: kotlin.String? = null, val file: java.io.File? = null)
+    @Resource("/pet/{petId}/uploadImage") class uploadFile(val petId: kotlin.Long)
 
     /**
      * Delete purchase order by ID
      * For valid response try integer IDs with value &lt; 1000. Anything above 1000 or nonintegers will generate API errors
      * @param orderId ID of the order that needs to be deleted 
      */
-    @Serializable @Resource("/store/order/{orderId}") class deleteOrder(val orderId: kotlin.String)
+    @Resource("/store/order/{orderId}") class deleteOrder(val orderId: kotlin.String)
 
     /**
      * Returns pet inventories by status
      * Returns a map of status codes to quantities
      */
-    @Serializable @Resource("/store/inventory") class getInventory
+    @Resource("/store/inventory") class getInventory
 
     /**
      * Find purchase order by ID
      * For valid response try integer IDs with value &lt;&#x3D; 5 or &gt; 10. Other values will generate exceptions
      * @param orderId ID of pet that needs to be fetched 
      */
-    @Serializable @Resource("/store/order/{orderId}") class getOrderById(val orderId: kotlin.Long)
+    @Resource("/store/order/{orderId}") class getOrderById(val orderId: kotlin.Long)
 
     /**
      * Place an order for a pet
      * 
      * @param body order placed for purchasing the pet 
      */
-    @Serializable @Resource("/store/order") class placeOrder(val body: Order)
+    @Resource("/store/order") class placeOrder()
 
     /**
      * Create user
      * This can only be done by the logged in user.
      * @param body Created user object 
      */
-    @Serializable @Resource("/user") class createUser(val body: User)
+    @Resource("/user") class createUser()
 
     /**
      * Creates list of users with given input array
      * 
      * @param body List of user object 
      */
-    @Serializable @Resource("/user/createWithArray") class createUsersWithArrayInput(val body: kotlin.collections.List<User>)
+    @Resource("/user/createWithArray") class createUsersWithArrayInput()
 
     /**
      * Creates list of users with given input array
      * 
      * @param body List of user object 
      */
-    @Serializable @Resource("/user/createWithList") class createUsersWithListInput(val body: kotlin.collections.List<User>)
+    @Resource("/user/createWithList") class createUsersWithListInput()
 
     /**
      * Delete user
      * This can only be done by the logged in user.
      * @param username The name that needs to be deleted 
      */
-    @Serializable @Resource("/user/{username}") class deleteUser(val username: kotlin.String)
+    @Resource("/user/{username}") class deleteUser(val username: kotlin.String)
 
     /**
      * Get user by user name
      * 
      * @param username The name that needs to be fetched. Use user1 for testing. 
      */
-    @Serializable @Resource("/user/{username}") class getUserByName(val username: kotlin.String)
+    @Resource("/user/{username}") class getUserByName(val username: kotlin.String)
 
     /**
      * Logs user into the system
@@ -145,13 +145,13 @@ object Paths {
      * @param username The user name for login 
      * @param password The password for login in clear text 
      */
-    @Serializable @Resource("/user/login") class loginUser(val username: kotlin.String, val password: kotlin.String)
+    @Resource("/user/login") class loginUser()
 
     /**
      * Logs out current logged in user session
      * 
      */
-    @Serializable @Resource("/user/logout") class logoutUser
+    @Resource("/user/logout") class logoutUser
 
     /**
      * Updated user
@@ -159,6 +159,6 @@ object Paths {
      * @param username name that need to be deleted 
      * @param body Updated user object 
      */
-    @Serializable @Resource("/user/{username}") class updateUser(val username: kotlin.String, val body: User)
+    @Resource("/user/{username}") class updateUser(val username: kotlin.String)
 
 }
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/PetApi.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
index d95a4b4d0883..b72ec0d72cec 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/PetApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -30,13 +29,12 @@ import org.openapitools.server.models.ModelApiResponse
 import org.openapitools.server.models.Pet
 
 fun Route.PetApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     authenticate("petstore_auth") {
     post<Paths.addPet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -47,7 +45,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     delete<Paths.deletePet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -58,7 +56,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     get<Paths.findPetsByStatus> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -97,7 +95,7 @@ fun Route.PetApi() {
             } ]"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -108,7 +106,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     get<Paths.findPetsByTags> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -147,7 +145,7 @@ fun Route.PetApi() {
             } ]"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -158,7 +156,7 @@ fun Route.PetApi() {
     authenticate("api_key") {
     get<Paths.getPetById> {
         
-        val principal = call.authentication.principal<ApiPrincipal>()!!
+        val principal = call.authentication.principal<ApiPrincipal>()
         
         
         val exampleContentType = "application/json"
@@ -181,7 +179,7 @@ fun Route.PetApi() {
             }"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
@@ -192,7 +190,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     put<Paths.updatePet> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -203,7 +201,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     post<Paths.updatePetWithForm> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -214,7 +212,7 @@ fun Route.PetApi() {
     authenticate("petstore_auth") {
     post<Paths.uploadFile> {
         
-        val principal = call.authentication.principal<OAuthAccessTokenResponse>()!!
+        val principal = call.authentication.principal<OAuthAccessTokenResponse>()
         
         
         val exampleContentType = "application/json"
@@ -225,7 +223,7 @@ fun Route.PetApi() {
             }"""
             
             when (exampleContentType) {
-                "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+                "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
                 "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
                 else -> call.respondText(exampleContentString)
             }
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
index fe780f7feb46..4a4395778401 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/StoreApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -29,7 +28,6 @@ import org.openapitools.server.infrastructure.ApiPrincipal
 import org.openapitools.server.models.Order
 
 fun Route.StoreApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     delete<Paths.deleteOrder> {
@@ -40,7 +38,7 @@ fun Route.StoreApi() {
     authenticate("api_key") {
     get<Paths.getInventory> {
         
-        val principal = call.authentication.principal<ApiPrincipal>()!!
+        val principal = call.authentication.principal<ApiPrincipal>()
         
         
         call.respond(HttpStatusCode.NotImplemented)
@@ -60,7 +58,7 @@ fun Route.StoreApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
@@ -79,7 +77,7 @@ fun Route.StoreApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/UserApi.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
index ccf0509fca2e..299f743e141d 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/apis/UserApi.kt
@@ -11,7 +11,6 @@
 */
 package org.openapitools.server.apis
 
-import com.google.gson.Gson
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.auth.*
@@ -29,7 +28,6 @@ import org.openapitools.server.infrastructure.ApiPrincipal
 import org.openapitools.server.models.User
 
 fun Route.UserApi() {
-    val gson = Gson()
     val empty = mutableMapOf<String, Any?>()
 
     post<Paths.createUser> {
@@ -66,7 +64,7 @@ fun Route.UserApi() {
         }"""
         
         when (exampleContentType) {
-            "application/json" -> call.respond(gson.fromJson(exampleContentString, empty::class.java))
+            "application/json" -> call.respondText(exampleContentType, ContentType.Application.Json)
             "application/xml" -> call.respondText(exampleContentString, ContentType.Text.Xml)
             else -> call.respondText(exampleContentString)
         }
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Category.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Category.kt
index 9d8571921384..7647c2d227e0 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Category.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Category.kt
@@ -12,19 +12,17 @@
 package org.openapitools.server.models
 
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * A category for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Category(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
index 5548175d9048..e16d42e86a4e 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/ModelApiResponse.kt
@@ -12,21 +12,19 @@
 package org.openapitools.server.models
 
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * Describes the result of uploading an image resource
  * @param code 
  * @param type 
  * @param message 
  */
+@Serializable
 data class ModelApiResponse(
     val code: kotlin.Int? = null,
     val type: kotlin.String? = null,
     val message: kotlin.String? = null
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Order.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Order.kt
index 79dce95e1e47..b1a711510fc6 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Order.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Order.kt
@@ -12,7 +12,7 @@
 package org.openapitools.server.models
 
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * An order for a pets from the pet store
  * @param id 
@@ -22,19 +22,17 @@ import java.io.Serializable
  * @param status Order Status
  * @param complete 
  */
+@Serializable
 data class Order(
     val id: kotlin.Long? = null,
     val petId: kotlin.Long? = null,
     val quantity: kotlin.Int? = null,
-    val shipDate: java.time.OffsetDateTime? = null,
+    val shipDate: kotlin.String? = null,
     /* Order Status */
     val status: Order.Status? = null,
     val complete: kotlin.Boolean? = false
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
     /**
     * Order Status
     * Values: placed,approved,delivered
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Pet.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Pet.kt
index 8b98ce0469c5..8fe934cc3ff3 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Pet.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Pet.kt
@@ -14,7 +14,7 @@ package org.openapitools.server.models
 import org.openapitools.server.models.Category
 import org.openapitools.server.models.Tag
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * A pet for sale in the pet store
  * @param name 
@@ -24,6 +24,7 @@ import java.io.Serializable
  * @param tags 
  * @param status pet status in the store
  */
+@Serializable
 data class Pet(
     val name: kotlin.String,
     val photoUrls: kotlin.collections.List<kotlin.String>,
@@ -32,11 +33,8 @@ data class Pet(
     val tags: kotlin.collections.List<Tag>? = null,
     /* pet status in the store */
     val status: Pet.Status? = null
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
     /**
     * pet status in the store
     * Values: available,pending,sold
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Tag.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Tag.kt
index e9626b25c6d1..fae4d9d0ba3c 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Tag.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/Tag.kt
@@ -12,19 +12,17 @@
 package org.openapitools.server.models
 
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * A tag for a pet
  * @param id 
  * @param name 
  */
+@Serializable
 data class Tag(
     val id: kotlin.Long? = null,
     val name: kotlin.String? = null
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
 }
 
diff --git a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/User.kt b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/User.kt
index fdbdb4e1cff4..af04fd61c1cf 100644
--- a/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/User.kt
+++ b/samples/server/petstore/kotlin-server/ktor/src/main/kotlin/org/openapitools/server/models/User.kt
@@ -12,7 +12,7 @@
 package org.openapitools.server.models
 
 
-import java.io.Serializable
+import kotlinx.serialization.Serializable
 /**
  * A User who is purchasing from the pet store
  * @param id 
@@ -24,6 +24,7 @@ import java.io.Serializable
  * @param phone 
  * @param userStatus User Status
  */
+@Serializable
 data class User(
     val id: kotlin.Long? = null,
     val username: kotlin.String? = null,
@@ -34,10 +35,7 @@ data class User(
     val phone: kotlin.String? = null,
     /* User Status */
     val userStatus: kotlin.Int? = null
-) : Serializable 
+)
 {
-    companion object {
-        private const val serialVersionUID: Long = 123
-    }
 }