diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/README.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/README.mustache
index d6dca22f5fc6..d805869f5ae0 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/README.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/README.mustache
@@ -20,8 +20,8 @@ For more information, please visit [{{{infoUrl}}}]({{{infoUrl}}})
 ## Requires
 
 {{#jvm}}
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 {{/jvm}}
 {{#multiplatform}}
 * Kotlin 1.5.10
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/build.gradle.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/build.gradle.mustache
index 5716f8656c32..e613a3d8f39d 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/build.gradle.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/build.gradle.mustache
@@ -11,7 +11,7 @@ wrapper {
 buildscript {
     ext.kotlin_version = '1.6.10'
     {{#jvm-ktor}}
-    ext.ktor_version = '2.0.3'
+    ext.ktor_version = '2.1.2'
     {{/jvm-ktor}}
     {{#jvm-retrofit2}}
     ext.retrofitVersion = '2.9.0'
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/infrastructure/ApiClient.kt.mustache
index 51a0a5f504e5..301af9194f8c 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/infrastructure/ApiClient.kt.mustache
@@ -12,6 +12,7 @@ import io.ktor.client.request.parameter
 import io.ktor.client.request.request
 import io.ktor.client.request.setBody
 import io.ktor.client.statement.HttpResponse
+import io.ktor.http.contentType
 import io.ktor.http.HttpHeaders
 import io.ktor.http.HttpMethod
 import io.ktor.http.Parameters
@@ -34,11 +35,6 @@ import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
 import com.fasterxml.jackson.core.util.DefaultIndenter
 import com.fasterxml.jackson.core.util.DefaultPrettyPrinter
 {{/jackson}}
-import org.openapitools.client.auth.ApiKeyAuth
-import org.openapitools.client.auth.Authentication
-import org.openapitools.client.auth.HttpBasicAuth
-import org.openapitools.client.auth.HttpBearerAuth
-import org.openapitools.client.auth.OAuth
 import {{packageName}}.auth.*
 
 {{#nonPublicApi}}internal {{/nonPublicApi}}open class ApiClient(
@@ -111,7 +107,7 @@ import {{packageName}}.auth.*
      * @param username Username
      */
     fun setUsername(username: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.username = username
     }
@@ -122,7 +118,7 @@ import {{packageName}}.auth.*
      * @param password Password
      */
     fun setPassword(password: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.password = password
     }
@@ -134,7 +130,7 @@ import {{packageName}}.auth.*
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKey(apiKey: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKey = apiKey
     }
@@ -146,7 +142,7 @@ import {{packageName}}.auth.*
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKeyPrefix(apiKeyPrefix: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKeyPrefix = apiKeyPrefix
     }
@@ -157,7 +153,7 @@ import {{packageName}}.auth.*
      * @param accessToken Access token
      */
     fun setAccessToken(accessToken: String) {
-        val auth = authentications.values.firstOrNull { it is OAuth } as OAuth?
+        val auth = authentications?.values?.firstOrNull { it is OAuth } as OAuth?
                 ?: throw Exception("No OAuth2 authentication configured")
         auth.accessToken = accessToken
     }
@@ -168,7 +164,7 @@ import {{packageName}}.auth.*
      * @param bearerToken The bearer token.
      */
     fun setBearerToken(bearerToken: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
                 ?: throw Exception("No Bearer authentication configured")
         auth.bearerToken = bearerToken
     }
@@ -199,8 +195,9 @@ import {{packageName}}.auth.*
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 setBody(body)
+            }
         }
     }
 
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/multiplatform/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/multiplatform/infrastructure/ApiClient.kt.mustache
index bc5d9b195081..bbed97d77aed 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/multiplatform/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/multiplatform/infrastructure/ApiClient.kt.mustache
@@ -4,13 +4,13 @@ import io.ktor.client.HttpClient
 import io.ktor.client.HttpClientConfig
 import io.ktor.client.engine.HttpClientEngine
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
-import io.ktor.serialization.kotlinx.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.FormDataContent
 import io.ktor.client.request.forms.MultiPartFormDataContent
 import io.ktor.client.request.header
 import io.ktor.client.request.parameter
 import io.ktor.client.statement.HttpResponse
+import io.ktor.serialization.kotlinx.json.json
 import io.ktor.http.*
 import io.ktor.http.content.PartData
 import kotlin.Unit
@@ -153,9 +153,9 @@ import {{packageName}}.auth.*
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 this.setBody(body)
-
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-allOff-discriminator/README.md b/samples/client/petstore/kotlin-allOff-discriminator/README.md
index 6b1ed0fb3219..b8f74b274242 100644
--- a/samples/client/petstore/kotlin-allOff-discriminator/README.md
+++ b/samples/client/petstore/kotlin-allOff-discriminator/README.md
@@ -12,8 +12,8 @@ For more information, please visit [https://example.org](https://example.org)
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/README.md b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/README.md
index be47543f9633..49b1c94dab68 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/README.md
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp3/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/README.md b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/README.md
index be47543f9633..49b1c94dab68 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/README.md
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-array-simple-string-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-array-simple-string-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index fd07e4229d10..529ae1e4d05f 100644
--- a/samples/client/petstore/kotlin-array-simple-string-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-array-simple-string-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -4,13 +4,13 @@ import io.ktor.client.HttpClient
 import io.ktor.client.HttpClientConfig
 import io.ktor.client.engine.HttpClientEngine
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
-import io.ktor.serialization.kotlinx.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.FormDataContent
 import io.ktor.client.request.forms.MultiPartFormDataContent
 import io.ktor.client.request.header
 import io.ktor.client.request.parameter
 import io.ktor.client.statement.HttpResponse
+import io.ktor.serialization.kotlinx.json.json
 import io.ktor.http.*
 import io.ktor.http.content.PartData
 import kotlin.Unit
@@ -142,9 +142,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 this.setBody(body)
-
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-bigdecimal-default-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-bigdecimal-default-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index fd07e4229d10..529ae1e4d05f 100644
--- a/samples/client/petstore/kotlin-bigdecimal-default-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-bigdecimal-default-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -4,13 +4,13 @@ import io.ktor.client.HttpClient
 import io.ktor.client.HttpClientConfig
 import io.ktor.client.engine.HttpClientEngine
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
-import io.ktor.serialization.kotlinx.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.FormDataContent
 import io.ktor.client.request.forms.MultiPartFormDataContent
 import io.ktor.client.request.header
 import io.ktor.client.request.parameter
 import io.ktor.client.statement.HttpResponse
+import io.ktor.serialization.kotlinx.json.json
 import io.ktor.http.*
 import io.ktor.http.content.PartData
 import kotlin.Unit
@@ -142,9 +142,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 this.setBody(body)
-
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/README.md b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/README.md
index e1589aead68a..ccbdb1a4e4a9 100644
--- a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/README.md
+++ b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp3/README.md b/samples/client/petstore/kotlin-default-values-jvm-okhttp3/README.md
index 96bddb2ac986..c1b435ada57c 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp3/README.md
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp3/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/README.md b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/README.md
index 96bddb2ac986..c1b435ada57c 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/README.md
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-default-values-jvm-retrofit2/README.md b/samples/client/petstore/kotlin-default-values-jvm-retrofit2/README.md
index 904786dd56bb..be72f0dfcf6c 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-retrofit2/README.md
+++ b/samples/client/petstore/kotlin-default-values-jvm-retrofit2/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-default-values-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-default-values-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index fd07e4229d10..529ae1e4d05f 100644
--- a/samples/client/petstore/kotlin-default-values-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-default-values-multiplatform/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -4,13 +4,13 @@ import io.ktor.client.HttpClient
 import io.ktor.client.HttpClientConfig
 import io.ktor.client.engine.HttpClientEngine
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
-import io.ktor.serialization.kotlinx.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.FormDataContent
 import io.ktor.client.request.forms.MultiPartFormDataContent
 import io.ktor.client.request.header
 import io.ktor.client.request.parameter
 import io.ktor.client.statement.HttpResponse
+import io.ktor.serialization.kotlinx.json.json
 import io.ktor.http.*
 import io.ktor.http.content.PartData
 import kotlin.Unit
@@ -142,9 +142,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 this.setBody(body)
-
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-enum-default-value/README.md b/samples/client/petstore/kotlin-enum-default-value/README.md
index df4685a2021a..665d73528702 100644
--- a/samples/client/petstore/kotlin-enum-default-value/README.md
+++ b/samples/client/petstore/kotlin-enum-default-value/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-gson/README.md b/samples/client/petstore/kotlin-gson/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-gson/README.md
+++ b/samples/client/petstore/kotlin-gson/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-jackson/README.md b/samples/client/petstore/kotlin-jackson/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-jackson/README.md
+++ b/samples/client/petstore/kotlin-jackson/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-json-request-string/README.md b/samples/client/petstore/kotlin-json-request-string/README.md
index eb18a4c21d8a..928a13052e77 100644
--- a/samples/client/petstore/kotlin-json-request-string/README.md
+++ b/samples/client/petstore/kotlin-json-request-string/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-jvm-ktor-gson/README.md b/samples/client/petstore/kotlin-jvm-ktor-gson/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-gson/README.md
+++ b/samples/client/petstore/kotlin-jvm-ktor-gson/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-jvm-ktor-gson/build.gradle b/samples/client/petstore/kotlin-jvm-ktor-gson/build.gradle
index 0c3e6b64c92a..67441d77a6a5 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-gson/build.gradle
+++ b/samples/client/petstore/kotlin-jvm-ktor-gson/build.gradle
@@ -8,7 +8,7 @@ wrapper {
 
 buildscript {
     ext.kotlin_version = '1.6.10'
-    ext.ktor_version = '2.0.3'
+    ext.ktor_version = '2.1.2'
 
     repositories {
         maven { url "https://repo1.maven.org/maven2" }
diff --git a/samples/client/petstore/kotlin-jvm-ktor-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jvm-ktor-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 5d6fc3af68b6..69c803dfbcf6 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jvm-ktor-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -12,6 +12,7 @@ import io.ktor.client.request.parameter
 import io.ktor.client.request.request
 import io.ktor.client.request.setBody
 import io.ktor.client.statement.HttpResponse
+import io.ktor.http.contentType
 import io.ktor.http.HttpHeaders
 import io.ktor.http.HttpMethod
 import io.ktor.http.Parameters
@@ -23,11 +24,6 @@ import io.ktor.http.takeFrom
 import io.ktor.serialization.gson.*
 import com.google.gson.GsonBuilder
 import java.text.DateFormat
-import org.openapitools.client.auth.ApiKeyAuth
-import org.openapitools.client.auth.Authentication
-import org.openapitools.client.auth.HttpBasicAuth
-import org.openapitools.client.auth.HttpBearerAuth
-import org.openapitools.client.auth.OAuth
 import org.openapitools.client.auth.*
 
 open class ApiClient(
@@ -71,7 +67,7 @@ open class ApiClient(
      * @param username Username
      */
     fun setUsername(username: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.username = username
     }
@@ -82,7 +78,7 @@ open class ApiClient(
      * @param password Password
      */
     fun setPassword(password: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.password = password
     }
@@ -94,7 +90,7 @@ open class ApiClient(
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKey(apiKey: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKey = apiKey
     }
@@ -106,7 +102,7 @@ open class ApiClient(
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKeyPrefix(apiKeyPrefix: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKeyPrefix = apiKeyPrefix
     }
@@ -117,7 +113,7 @@ open class ApiClient(
      * @param accessToken Access token
      */
     fun setAccessToken(accessToken: String) {
-        val auth = authentications.values.firstOrNull { it is OAuth } as OAuth?
+        val auth = authentications?.values?.firstOrNull { it is OAuth } as OAuth?
                 ?: throw Exception("No OAuth2 authentication configured")
         auth.accessToken = accessToken
     }
@@ -128,7 +124,7 @@ open class ApiClient(
      * @param bearerToken The bearer token.
      */
     fun setBearerToken(bearerToken: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
                 ?: throw Exception("No Bearer authentication configured")
         auth.bearerToken = bearerToken
     }
@@ -159,8 +155,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 setBody(body)
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-jvm-ktor-jackson/README.md b/samples/client/petstore/kotlin-jvm-ktor-jackson/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-jackson/README.md
+++ b/samples/client/petstore/kotlin-jvm-ktor-jackson/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-jvm-ktor-jackson/build.gradle b/samples/client/petstore/kotlin-jvm-ktor-jackson/build.gradle
index febcd440b1e9..072128b1cecb 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-jackson/build.gradle
+++ b/samples/client/petstore/kotlin-jvm-ktor-jackson/build.gradle
@@ -8,7 +8,7 @@ wrapper {
 
 buildscript {
     ext.kotlin_version = '1.6.10'
-    ext.ktor_version = '2.0.3'
+    ext.ktor_version = '2.1.2'
 
     repositories {
         maven { url "https://repo1.maven.org/maven2" }
diff --git a/samples/client/petstore/kotlin-jvm-ktor-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jvm-ktor-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index e21bccb90604..bb3a5290cf6e 100644
--- a/samples/client/petstore/kotlin-jvm-ktor-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jvm-ktor-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -12,6 +12,7 @@ import io.ktor.client.request.parameter
 import io.ktor.client.request.request
 import io.ktor.client.request.setBody
 import io.ktor.client.statement.HttpResponse
+import io.ktor.http.contentType
 import io.ktor.http.HttpHeaders
 import io.ktor.http.HttpMethod
 import io.ktor.http.Parameters
@@ -27,11 +28,6 @@ import com.fasterxml.jackson.databind.SerializationFeature
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
 import com.fasterxml.jackson.core.util.DefaultIndenter
 import com.fasterxml.jackson.core.util.DefaultPrettyPrinter
-import org.openapitools.client.auth.ApiKeyAuth
-import org.openapitools.client.auth.Authentication
-import org.openapitools.client.auth.HttpBasicAuth
-import org.openapitools.client.auth.HttpBearerAuth
-import org.openapitools.client.auth.OAuth
 import org.openapitools.client.auth.*
 
 open class ApiClient(
@@ -79,7 +75,7 @@ open class ApiClient(
      * @param username Username
      */
     fun setUsername(username: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.username = username
     }
@@ -90,7 +86,7 @@ open class ApiClient(
      * @param password Password
      */
     fun setPassword(password: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBasicAuth } as HttpBasicAuth?
                 ?: throw Exception("No HTTP basic authentication configured")
         auth.password = password
     }
@@ -102,7 +98,7 @@ open class ApiClient(
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKey(apiKey: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName)} as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKey = apiKey
     }
@@ -114,7 +110,7 @@ open class ApiClient(
      * @param paramName The name of the API key parameter, or null or set the first key.
      */
     fun setApiKeyPrefix(apiKeyPrefix: String, paramName: String? = null) {
-        val auth = authentications.values.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
+        val auth = authentications?.values?.firstOrNull { it is ApiKeyAuth && (paramName == null || paramName == it.paramName) } as ApiKeyAuth?
                 ?: throw Exception("No API key authentication configured")
         auth.apiKeyPrefix = apiKeyPrefix
     }
@@ -125,7 +121,7 @@ open class ApiClient(
      * @param accessToken Access token
      */
     fun setAccessToken(accessToken: String) {
-        val auth = authentications.values.firstOrNull { it is OAuth } as OAuth?
+        val auth = authentications?.values?.firstOrNull { it is OAuth } as OAuth?
                 ?: throw Exception("No OAuth2 authentication configured")
         auth.accessToken = accessToken
     }
@@ -136,7 +132,7 @@ open class ApiClient(
      * @param bearerToken The bearer token.
      */
     fun setBearerToken(bearerToken: String) {
-        val auth = authentications.values.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
+        val auth = authentications?.values?.firstOrNull { it is HttpBearerAuth } as HttpBearerAuth?
                 ?: throw Exception("No Bearer authentication configured")
         auth.bearerToken = bearerToken
     }
@@ -167,8 +163,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 setBody(body)
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/README.md b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/README.md
+++ b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-modelMutable/README.md b/samples/client/petstore/kotlin-modelMutable/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-modelMutable/README.md
+++ b/samples/client/petstore/kotlin-modelMutable/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-moshi-codegen/README.md b/samples/client/petstore/kotlin-moshi-codegen/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-moshi-codegen/README.md
+++ b/samples/client/petstore/kotlin-moshi-codegen/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-multiplatform/src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-multiplatform/src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index dc660734191a..35e549b98296 100644
--- a/samples/client/petstore/kotlin-multiplatform/src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-multiplatform/src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -4,13 +4,13 @@ import io.ktor.client.HttpClient
 import io.ktor.client.HttpClientConfig
 import io.ktor.client.engine.HttpClientEngine
 import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
-import io.ktor.serialization.kotlinx.json.*
 import io.ktor.client.request.*
 import io.ktor.client.request.forms.FormDataContent
 import io.ktor.client.request.forms.MultiPartFormDataContent
 import io.ktor.client.request.header
 import io.ktor.client.request.parameter
 import io.ktor.client.statement.HttpResponse
+import io.ktor.serialization.kotlinx.json.json
 import io.ktor.http.*
 import io.ktor.http.content.PartData
 import kotlin.Unit
@@ -146,9 +146,9 @@ open class ApiClient(
             }
             this.method = requestConfig.method.httpMethod
             headers.filter { header -> !UNSAFE_HEADERS.contains(header.key) }.forEach { header -> this.header(header.key, header.value) }
-            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH))
+            if (requestConfig.method in listOf(RequestMethod.PUT, RequestMethod.POST, RequestMethod.PATCH)) {
                 this.setBody(body)
-
+            }
         }
     }
 
diff --git a/samples/client/petstore/kotlin-nonpublic/README.md b/samples/client/petstore/kotlin-nonpublic/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-nonpublic/README.md
+++ b/samples/client/petstore/kotlin-nonpublic/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-nullable/README.md b/samples/client/petstore/kotlin-nullable/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-nullable/README.md
+++ b/samples/client/petstore/kotlin-nullable/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-okhttp3/README.md b/samples/client/petstore/kotlin-okhttp3/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-okhttp3/README.md
+++ b/samples/client/petstore/kotlin-okhttp3/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/README.md b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/README.md
index 1bd530b89967..473c874b300b 100644
--- a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/README.md
+++ b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-retrofit2-rx3/README.md b/samples/client/petstore/kotlin-retrofit2-rx3/README.md
index 1bd530b89967..473c874b300b 100644
--- a/samples/client/petstore/kotlin-retrofit2-rx3/README.md
+++ b/samples/client/petstore/kotlin-retrofit2-rx3/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-retrofit2/README.md b/samples/client/petstore/kotlin-retrofit2/README.md
index 1bd530b89967..473c874b300b 100644
--- a/samples/client/petstore/kotlin-retrofit2/README.md
+++ b/samples/client/petstore/kotlin-retrofit2/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-string/README.md b/samples/client/petstore/kotlin-string/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-string/README.md
+++ b/samples/client/petstore/kotlin-string/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-threetenbp/README.md b/samples/client/petstore/kotlin-threetenbp/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin-threetenbp/README.md
+++ b/samples/client/petstore/kotlin-threetenbp/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin-uppercase-enum/README.md b/samples/client/petstore/kotlin-uppercase-enum/README.md
index 9b3bfe4e89ef..40a6b5fa1abb 100644
--- a/samples/client/petstore/kotlin-uppercase-enum/README.md
+++ b/samples/client/petstore/kotlin-uppercase-enum/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build
 
diff --git a/samples/client/petstore/kotlin/README.md b/samples/client/petstore/kotlin/README.md
index e8336e9f36b1..e3f2108bfcdc 100644
--- a/samples/client/petstore/kotlin/README.md
+++ b/samples/client/petstore/kotlin/README.md
@@ -11,8 +11,8 @@ This API client was generated by the [OpenAPI Generator](https://openapi-generat
 
 ## Requires
 
-* Kotlin 1.4.30
-* Gradle 6.8.3
+* Kotlin 1.6.10
+* Gradle 7.5
 
 ## Build