diff --git a/modules/openapi-generator/src/main/resources/dart/api_client.mustache b/modules/openapi-generator/src/main/resources/dart/api_client.mustache
index e8e6a515b4..8d3e706d3e 100644
--- a/modules/openapi-generator/src/main/resources/dart/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/dart/api_client.mustache
@@ -109,7 +109,10 @@ class ApiClient {
 
     _updateParamsForAuth(authNames, queryParams, headerParams);
 
-    var ps = queryParams.where((p) => p.value != null).map((p) => '${p.name}=${p.value}');
+    var ps = queryParams
+      .where((p) => p.value != null)
+      .map((p) => '${p.name}=${Uri.encodeQueryComponent(p.value)}');
+
     String queryString = ps.isNotEmpty ?
                          '?' + ps.join('&') :
                          '';
diff --git a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
index a3cd3c2463..2a6c411a78 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
@@ -109,7 +109,10 @@ class ApiClient {
 
     _updateParamsForAuth(authNames, queryParams, headerParams);
 
-    var ps = queryParams.where((p) => p.value != null).map((p) => '${p.name}=${p.value}');
+    var ps = queryParams
+      .where((p) => p.value != null)
+      .map((p) => '${p.name}=${Uri.encodeQueryComponent(p.value)}');
+
     String queryString = ps.isNotEmpty ?
                          '?' + ps.join('&') :
                          '';
diff --git a/samples/client/petstore/dart-jaguar/flutter_petstore/openapi/README.md b/samples/client/petstore/dart-jaguar/flutter_petstore/openapi/README.md
index 666fd69e73..a87129d5a9 100644
--- a/samples/client/petstore/dart-jaguar/flutter_petstore/openapi/README.md
+++ b/samples/client/petstore/dart-jaguar/flutter_petstore/openapi/README.md
@@ -4,7 +4,7 @@ This is a sample server Petstore server. For this sample, you can use the api ke
 This Dart package is automatically generated by the [Open API Codegen](https://github.com/OpenAPITools/openapi-generator) project:
 
 - API version: 1.0.0
-- Build date: 2019-01-17T18:23:25.026381+01:00[Europe/Vienna]
+- Build date: 2019-02-26T17:35:06.224333+01:00[Europe/Vienna]
 - Build package: org.openapitools.codegen.languages.DartJaguarClientCodegen
 
 ## Requirements
diff --git a/samples/client/petstore/dart-jaguar/openapi/README.md b/samples/client/petstore/dart-jaguar/openapi/README.md
index 6bab772c25..77ff710e9f 100644
--- a/samples/client/petstore/dart-jaguar/openapi/README.md
+++ b/samples/client/petstore/dart-jaguar/openapi/README.md
@@ -4,7 +4,7 @@ This is a sample server Petstore server. For this sample, you can use the api ke
 This Dart package is automatically generated by the [Open API Codegen](https://github.com/OpenAPITools/openapi-generator) project:
 
 - API version: 1.0.0
-- Build date: 2019-01-17T18:23:23.279159+01:00[Europe/Vienna]
+- Build date: 2019-02-26T17:35:04.597991+01:00[Europe/Vienna]
 - Build package: org.openapitools.codegen.languages.DartJaguarClientCodegen
 
 ## Requirements
diff --git a/samples/client/petstore/dart/flutter_petstore/openapi/lib/api_client.dart b/samples/client/petstore/dart/flutter_petstore/openapi/lib/api_client.dart
index db4116dd96..b99ddeeccb 100644
--- a/samples/client/petstore/dart/flutter_petstore/openapi/lib/api_client.dart
+++ b/samples/client/petstore/dart/flutter_petstore/openapi/lib/api_client.dart
@@ -105,7 +105,10 @@ class ApiClient {
 
     _updateParamsForAuth(authNames, queryParams, headerParams);
 
-    var ps = queryParams.where((p) => p.value != null).map((p) => '${p.name}=${p.value}');
+    var ps = queryParams
+      .where((p) => p.value != null)
+      .map((p) => '${p.name}=${Uri.encodeQueryComponent(p.value)}');
+
     String queryString = ps.isNotEmpty ?
                          '?' + ps.join('&') :
                          '';
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/pet_api.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/pet_api.dart
index abe86a5698..2ded9e38bf 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/pet_api.dart
@@ -50,7 +50,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -100,7 +100,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -150,9 +150,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -201,9 +201,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -251,9 +251,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return apiClient.deserialize(response.body, 'Pet') as Pet;
     } else {
       return null;
     }
@@ -301,7 +301,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -362,7 +362,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -422,9 +422,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return apiClient.deserialize(response.body, 'ApiResponse') as ApiResponse;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/store_api.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/store_api.dart
index 75d6ef034c..0d05ff39bc 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/store_api.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/store_api.dart
@@ -50,7 +50,7 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -96,9 +96,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return new Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return new Map<String, int>.from(apiClient.deserialize(response.body, 'Map<String, int>'));
           ;
     } else {
       return null;
@@ -147,9 +147,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
@@ -197,9 +197,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/user_api.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/user_api.dart
index a4be03b431..91d35801e4 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/user_api.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api/user_api.dart
@@ -50,7 +50,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -99,7 +99,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -148,7 +148,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -197,7 +197,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -246,9 +246,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return apiClient.deserialize(response.body, 'User') as User;
     } else {
       return null;
     }
@@ -301,9 +301,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return apiClient.deserialize(response.body, 'String') as String;
     } else {
       return null;
     }
@@ -348,7 +348,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -400,7 +400,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api_helper.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api_helper.dart
index c57b111ca8..a516a68d26 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/api_helper.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/api_helper.dart
@@ -42,15 +42,3 @@ String parameterToString(dynamic value) {
     return value.toString();
   }
 }
-
-/// Returns the decoded body by utf-8 if application/json with the given headers.
-/// Else, returns the decoded body by default algorithm of dart:http.
-/// Because avoid to text garbling when header only contains "application/json" without "; charset=utf-8".
-String _decodeBodyBytes(Response response) {
-  var contentType = response.headers['content-type'];
-  if (contentType != null && contentType.contains("application/json")) {
-    return utf8.decode(response.bodyBytes);
-  } else {
-    return response.body;
-  }
-}
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/api_response.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/api_response.dart
index 99ffe708ae..37c961b732 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/api_response.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/api_response.dart
@@ -19,17 +19,17 @@ class ApiResponse {
     if (json['code'] == null) {
       code = null;
     } else {
-          code = json['code'];
+      code = json['code'];
     }
     if (json['type'] == null) {
       type = null;
     } else {
-          type = json['type'];
+      type = json['type'];
     }
     if (json['message'] == null) {
       message = null;
     } else {
-          message = json['message'];
+      message = json['message'];
     }
   }
 
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/category.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/category.dart
index 19386463ba..862b2c5b38 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/category.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/category.dart
@@ -17,12 +17,12 @@ class Category {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/order.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/order.dart
index e9dfcfeaa9..42dc28f0fa 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/order.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/order.dart
@@ -26,17 +26,17 @@ class Order {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['petId'] == null) {
       petId = null;
     } else {
-          petId = json['petId'];
+      petId = json['petId'];
     }
     if (json['quantity'] == null) {
       quantity = null;
     } else {
-          quantity = json['quantity'];
+      quantity = json['quantity'];
     }
     if (json['shipDate'] == null) {
       shipDate = null;
@@ -46,12 +46,12 @@ class Order {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
     if (json['complete'] == null) {
       complete = null;
     } else {
-          complete = json['complete'];
+      complete = json['complete'];
     }
   }
 
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/pet.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/pet.dart
index 73407dc7dd..f7747b01cf 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/pet.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/pet.dart
@@ -26,7 +26,7 @@ class Pet {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['category'] == null) {
       category = null;
@@ -36,12 +36,12 @@ class Pet {
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
     if (json['photoUrls'] == null) {
       photoUrls = null;
     } else {
-      photoUrls = (json['photoUrls'] as List).cast<String>();
+      photoUrls = ((json['photoUrls'] ?? []) as List).map((item) => item as String).toList();
     }
     if (json['tags'] == null) {
       tags = null;
@@ -51,7 +51,7 @@ class Pet {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
   }
 
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/tag.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/tag.dart
index 7bd96004c2..964fa48e0e 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/tag.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/tag.dart
@@ -17,12 +17,12 @@ class Tag {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/user.dart b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/user.dart
index 0178b53944..067ce8f5c8 100644
--- a/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/user.dart
+++ b/samples/client/petstore/dart/flutter_petstore/swagger/lib/model/user.dart
@@ -29,42 +29,42 @@ class User {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['username'] == null) {
       username = null;
     } else {
-          username = json['username'];
+      username = json['username'];
     }
     if (json['firstName'] == null) {
       firstName = null;
     } else {
-          firstName = json['firstName'];
+      firstName = json['firstName'];
     }
     if (json['lastName'] == null) {
       lastName = null;
     } else {
-          lastName = json['lastName'];
+      lastName = json['lastName'];
     }
     if (json['email'] == null) {
       email = null;
     } else {
-          email = json['email'];
+      email = json['email'];
     }
     if (json['password'] == null) {
       password = null;
     } else {
-          password = json['password'];
+      password = json['password'];
     }
     if (json['phone'] == null) {
       phone = null;
     } else {
-          phone = json['phone'];
+      phone = json['phone'];
     }
     if (json['userStatus'] == null) {
       userStatus = null;
     } else {
-          userStatus = json['userStatus'];
+      userStatus = json['userStatus'];
     }
   }
 
diff --git a/samples/client/petstore/dart/openapi-browser-client/lib/api_client.dart b/samples/client/petstore/dart/openapi-browser-client/lib/api_client.dart
index 7cca5bef5f..4875b70b97 100644
--- a/samples/client/petstore/dart/openapi-browser-client/lib/api_client.dart
+++ b/samples/client/petstore/dart/openapi-browser-client/lib/api_client.dart
@@ -105,7 +105,10 @@ class ApiClient {
 
     _updateParamsForAuth(authNames, queryParams, headerParams);
 
-    var ps = queryParams.where((p) => p.value != null).map((p) => '${p.name}=${p.value}');
+    var ps = queryParams
+      .where((p) => p.value != null)
+      .map((p) => '${p.name}=${Uri.encodeQueryComponent(p.value)}');
+
     String queryString = ps.isNotEmpty ?
                          '?' + ps.join('&') :
                          '';
diff --git a/samples/client/petstore/dart/openapi/lib/api_client.dart b/samples/client/petstore/dart/openapi/lib/api_client.dart
index db4116dd96..b99ddeeccb 100644
--- a/samples/client/petstore/dart/openapi/lib/api_client.dart
+++ b/samples/client/petstore/dart/openapi/lib/api_client.dart
@@ -105,7 +105,10 @@ class ApiClient {
 
     _updateParamsForAuth(authNames, queryParams, headerParams);
 
-    var ps = queryParams.where((p) => p.value != null).map((p) => '${p.name}=${p.value}');
+    var ps = queryParams
+      .where((p) => p.value != null)
+      .map((p) => '${p.name}=${Uri.encodeQueryComponent(p.value)}');
+
     String queryString = ps.isNotEmpty ?
                          '?' + ps.join('&') :
                          '';
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/pet_api.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/pet_api.dart
index abe86a5698..2ded9e38bf 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/pet_api.dart
@@ -50,7 +50,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -100,7 +100,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -150,9 +150,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -201,9 +201,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -251,9 +251,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return apiClient.deserialize(response.body, 'Pet') as Pet;
     } else {
       return null;
     }
@@ -301,7 +301,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -362,7 +362,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -422,9 +422,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return apiClient.deserialize(response.body, 'ApiResponse') as ApiResponse;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/store_api.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/store_api.dart
index 75d6ef034c..0d05ff39bc 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/store_api.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/store_api.dart
@@ -50,7 +50,7 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -96,9 +96,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return new Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return new Map<String, int>.from(apiClient.deserialize(response.body, 'Map<String, int>'));
           ;
     } else {
       return null;
@@ -147,9 +147,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
@@ -197,9 +197,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/user_api.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/user_api.dart
index a4be03b431..91d35801e4 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api/user_api.dart
@@ -50,7 +50,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -99,7 +99,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -148,7 +148,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -197,7 +197,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -246,9 +246,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return apiClient.deserialize(response.body, 'User') as User;
     } else {
       return null;
     }
@@ -301,9 +301,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return apiClient.deserialize(response.body, 'String') as String;
     } else {
       return null;
     }
@@ -348,7 +348,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -400,7 +400,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api_helper.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api_helper.dart
index c57b111ca8..a516a68d26 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api_helper.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/api_helper.dart
@@ -42,15 +42,3 @@ String parameterToString(dynamic value) {
     return value.toString();
   }
 }
-
-/// Returns the decoded body by utf-8 if application/json with the given headers.
-/// Else, returns the decoded body by default algorithm of dart:http.
-/// Because avoid to text garbling when header only contains "application/json" without "; charset=utf-8".
-String _decodeBodyBytes(Response response) {
-  var contentType = response.headers['content-type'];
-  if (contentType != null && contentType.contains("application/json")) {
-    return utf8.decode(response.bodyBytes);
-  } else {
-    return response.body;
-  }
-}
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/api_response.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/api_response.dart
index 99ffe708ae..37c961b732 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/api_response.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/api_response.dart
@@ -19,17 +19,17 @@ class ApiResponse {
     if (json['code'] == null) {
       code = null;
     } else {
-          code = json['code'];
+      code = json['code'];
     }
     if (json['type'] == null) {
       type = null;
     } else {
-          type = json['type'];
+      type = json['type'];
     }
     if (json['message'] == null) {
       message = null;
     } else {
-          message = json['message'];
+      message = json['message'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/category.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/category.dart
index 19386463ba..862b2c5b38 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/category.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/category.dart
@@ -17,12 +17,12 @@ class Category {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/order.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/order.dart
index e9dfcfeaa9..42dc28f0fa 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/order.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/order.dart
@@ -26,17 +26,17 @@ class Order {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['petId'] == null) {
       petId = null;
     } else {
-          petId = json['petId'];
+      petId = json['petId'];
     }
     if (json['quantity'] == null) {
       quantity = null;
     } else {
-          quantity = json['quantity'];
+      quantity = json['quantity'];
     }
     if (json['shipDate'] == null) {
       shipDate = null;
@@ -46,12 +46,12 @@ class Order {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
     if (json['complete'] == null) {
       complete = null;
     } else {
-          complete = json['complete'];
+      complete = json['complete'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/pet.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/pet.dart
index 73407dc7dd..f7747b01cf 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/pet.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/pet.dart
@@ -26,7 +26,7 @@ class Pet {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['category'] == null) {
       category = null;
@@ -36,12 +36,12 @@ class Pet {
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
     if (json['photoUrls'] == null) {
       photoUrls = null;
     } else {
-      photoUrls = (json['photoUrls'] as List).cast<String>();
+      photoUrls = ((json['photoUrls'] ?? []) as List).map((item) => item as String).toList();
     }
     if (json['tags'] == null) {
       tags = null;
@@ -51,7 +51,7 @@ class Pet {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/tag.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/tag.dart
index 7bd96004c2..964fa48e0e 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/tag.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/tag.dart
@@ -17,12 +17,12 @@ class Tag {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/user.dart b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/user.dart
index 0178b53944..067ce8f5c8 100644
--- a/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/user.dart
+++ b/samples/client/petstore/dart2/flutter_petstore/openapi/lib/model/user.dart
@@ -29,42 +29,42 @@ class User {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['username'] == null) {
       username = null;
     } else {
-          username = json['username'];
+      username = json['username'];
     }
     if (json['firstName'] == null) {
       firstName = null;
     } else {
-          firstName = json['firstName'];
+      firstName = json['firstName'];
     }
     if (json['lastName'] == null) {
       lastName = null;
     } else {
-          lastName = json['lastName'];
+      lastName = json['lastName'];
     }
     if (json['email'] == null) {
       email = null;
     } else {
-          email = json['email'];
+      email = json['email'];
     }
     if (json['password'] == null) {
       password = null;
     } else {
-          password = json['password'];
+      password = json['password'];
     }
     if (json['phone'] == null) {
       phone = null;
     } else {
-          phone = json['phone'];
+      phone = json['phone'];
     }
     if (json['userStatus'] == null) {
       userStatus = null;
     } else {
-          userStatus = json['userStatus'];
+      userStatus = json['userStatus'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/api/pet_api.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/api/pet_api.dart
index abe86a5698..2ded9e38bf 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/api/pet_api.dart
@@ -50,7 +50,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -100,7 +100,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -150,9 +150,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -201,9 +201,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -251,9 +251,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return apiClient.deserialize(response.body, 'Pet') as Pet;
     } else {
       return null;
     }
@@ -301,7 +301,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -362,7 +362,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -422,9 +422,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return apiClient.deserialize(response.body, 'ApiResponse') as ApiResponse;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/api/store_api.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/api/store_api.dart
index 75d6ef034c..0d05ff39bc 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/api/store_api.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/api/store_api.dart
@@ -50,7 +50,7 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -96,9 +96,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return new Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return new Map<String, int>.from(apiClient.deserialize(response.body, 'Map<String, int>'));
           ;
     } else {
       return null;
@@ -147,9 +147,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
@@ -197,9 +197,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/api/user_api.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/api/user_api.dart
index a4be03b431..91d35801e4 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/api/user_api.dart
@@ -50,7 +50,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -99,7 +99,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -148,7 +148,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -197,7 +197,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -246,9 +246,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return apiClient.deserialize(response.body, 'User') as User;
     } else {
       return null;
     }
@@ -301,9 +301,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return apiClient.deserialize(response.body, 'String') as String;
     } else {
       return null;
     }
@@ -348,7 +348,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -400,7 +400,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/api_helper.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/api_helper.dart
index c57b111ca8..a516a68d26 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/api_helper.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/api_helper.dart
@@ -42,15 +42,3 @@ String parameterToString(dynamic value) {
     return value.toString();
   }
 }
-
-/// Returns the decoded body by utf-8 if application/json with the given headers.
-/// Else, returns the decoded body by default algorithm of dart:http.
-/// Because avoid to text garbling when header only contains "application/json" without "; charset=utf-8".
-String _decodeBodyBytes(Response response) {
-  var contentType = response.headers['content-type'];
-  if (contentType != null && contentType.contains("application/json")) {
-    return utf8.decode(response.bodyBytes);
-  } else {
-    return response.body;
-  }
-}
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/api_response.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/api_response.dart
index 99ffe708ae..37c961b732 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/api_response.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/api_response.dart
@@ -19,17 +19,17 @@ class ApiResponse {
     if (json['code'] == null) {
       code = null;
     } else {
-          code = json['code'];
+      code = json['code'];
     }
     if (json['type'] == null) {
       type = null;
     } else {
-          type = json['type'];
+      type = json['type'];
     }
     if (json['message'] == null) {
       message = null;
     } else {
-          message = json['message'];
+      message = json['message'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/category.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/category.dart
index 19386463ba..862b2c5b38 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/category.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/category.dart
@@ -17,12 +17,12 @@ class Category {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/order.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/order.dart
index e9dfcfeaa9..42dc28f0fa 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/order.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/order.dart
@@ -26,17 +26,17 @@ class Order {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['petId'] == null) {
       petId = null;
     } else {
-          petId = json['petId'];
+      petId = json['petId'];
     }
     if (json['quantity'] == null) {
       quantity = null;
     } else {
-          quantity = json['quantity'];
+      quantity = json['quantity'];
     }
     if (json['shipDate'] == null) {
       shipDate = null;
@@ -46,12 +46,12 @@ class Order {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
     if (json['complete'] == null) {
       complete = null;
     } else {
-          complete = json['complete'];
+      complete = json['complete'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/pet.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/pet.dart
index 73407dc7dd..f7747b01cf 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/pet.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/pet.dart
@@ -26,7 +26,7 @@ class Pet {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['category'] == null) {
       category = null;
@@ -36,12 +36,12 @@ class Pet {
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
     if (json['photoUrls'] == null) {
       photoUrls = null;
     } else {
-      photoUrls = (json['photoUrls'] as List).cast<String>();
+      photoUrls = ((json['photoUrls'] ?? []) as List).map((item) => item as String).toList();
     }
     if (json['tags'] == null) {
       tags = null;
@@ -51,7 +51,7 @@ class Pet {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/tag.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/tag.dart
index 7bd96004c2..964fa48e0e 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/tag.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/tag.dart
@@ -17,12 +17,12 @@ class Tag {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi-browser-client/lib/model/user.dart b/samples/client/petstore/dart2/openapi-browser-client/lib/model/user.dart
index 0178b53944..067ce8f5c8 100644
--- a/samples/client/petstore/dart2/openapi-browser-client/lib/model/user.dart
+++ b/samples/client/petstore/dart2/openapi-browser-client/lib/model/user.dart
@@ -29,42 +29,42 @@ class User {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['username'] == null) {
       username = null;
     } else {
-          username = json['username'];
+      username = json['username'];
     }
     if (json['firstName'] == null) {
       firstName = null;
     } else {
-          firstName = json['firstName'];
+      firstName = json['firstName'];
     }
     if (json['lastName'] == null) {
       lastName = null;
     } else {
-          lastName = json['lastName'];
+      lastName = json['lastName'];
     }
     if (json['email'] == null) {
       email = null;
     } else {
-          email = json['email'];
+      email = json['email'];
     }
     if (json['password'] == null) {
       password = null;
     } else {
-          password = json['password'];
+      password = json['password'];
     }
     if (json['phone'] == null) {
       phone = null;
     } else {
-          phone = json['phone'];
+      phone = json['phone'];
     }
     if (json['userStatus'] == null) {
       userStatus = null;
     } else {
-          userStatus = json['userStatus'];
+      userStatus = json['userStatus'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/api/pet_api.dart b/samples/client/petstore/dart2/openapi/lib/api/pet_api.dart
index abe86a5698..2ded9e38bf 100644
--- a/samples/client/petstore/dart2/openapi/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/openapi/lib/api/pet_api.dart
@@ -50,7 +50,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -100,7 +100,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -150,9 +150,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -201,9 +201,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List).map((item) => item as Pet).toList();
+      return (apiClient.deserialize(response.body, 'List<Pet>') as List).map((item) => item as Pet).toList();
     } else {
       return null;
     }
@@ -251,9 +251,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return apiClient.deserialize(response.body, 'Pet') as Pet;
     } else {
       return null;
     }
@@ -301,7 +301,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -362,7 +362,7 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -422,9 +422,9 @@ class PetApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return apiClient.deserialize(response.body, 'ApiResponse') as ApiResponse;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/openapi/lib/api/store_api.dart b/samples/client/petstore/dart2/openapi/lib/api/store_api.dart
index 75d6ef034c..0d05ff39bc 100644
--- a/samples/client/petstore/dart2/openapi/lib/api/store_api.dart
+++ b/samples/client/petstore/dart2/openapi/lib/api/store_api.dart
@@ -50,7 +50,7 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -96,9 +96,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return new Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return new Map<String, int>.from(apiClient.deserialize(response.body, 'Map<String, int>'));
           ;
     } else {
       return null;
@@ -147,9 +147,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
@@ -197,9 +197,9 @@ class StoreApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return apiClient.deserialize(response.body, 'Order') as Order;
     } else {
       return null;
     }
diff --git a/samples/client/petstore/dart2/openapi/lib/api/user_api.dart b/samples/client/petstore/dart2/openapi/lib/api/user_api.dart
index a4be03b431..91d35801e4 100644
--- a/samples/client/petstore/dart2/openapi/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/openapi/lib/api/user_api.dart
@@ -50,7 +50,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -99,7 +99,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -148,7 +148,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -197,7 +197,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -246,9 +246,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return apiClient.deserialize(response.body, 'User') as User;
     } else {
       return null;
     }
@@ -301,9 +301,9 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return apiClient.deserialize(response.body, 'String') as String;
     } else {
       return null;
     }
@@ -348,7 +348,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
@@ -400,7 +400,7 @@ class UserApi {
                                              authNames);
 
     if(response.statusCode >= 400) {
-      throw new ApiException(response.statusCode, _decodeBodyBytes(response));
+      throw new ApiException(response.statusCode, response.body);
     } else if(response.body != null) {
     } else {
       return;
diff --git a/samples/client/petstore/dart2/openapi/lib/api_helper.dart b/samples/client/petstore/dart2/openapi/lib/api_helper.dart
index c57b111ca8..a516a68d26 100644
--- a/samples/client/petstore/dart2/openapi/lib/api_helper.dart
+++ b/samples/client/petstore/dart2/openapi/lib/api_helper.dart
@@ -42,15 +42,3 @@ String parameterToString(dynamic value) {
     return value.toString();
   }
 }
-
-/// Returns the decoded body by utf-8 if application/json with the given headers.
-/// Else, returns the decoded body by default algorithm of dart:http.
-/// Because avoid to text garbling when header only contains "application/json" without "; charset=utf-8".
-String _decodeBodyBytes(Response response) {
-  var contentType = response.headers['content-type'];
-  if (contentType != null && contentType.contains("application/json")) {
-    return utf8.decode(response.bodyBytes);
-  } else {
-    return response.body;
-  }
-}
diff --git a/samples/client/petstore/dart2/openapi/lib/model/api_response.dart b/samples/client/petstore/dart2/openapi/lib/model/api_response.dart
index 99ffe708ae..37c961b732 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/api_response.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/api_response.dart
@@ -19,17 +19,17 @@ class ApiResponse {
     if (json['code'] == null) {
       code = null;
     } else {
-          code = json['code'];
+      code = json['code'];
     }
     if (json['type'] == null) {
       type = null;
     } else {
-          type = json['type'];
+      type = json['type'];
     }
     if (json['message'] == null) {
       message = null;
     } else {
-          message = json['message'];
+      message = json['message'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/model/category.dart b/samples/client/petstore/dart2/openapi/lib/model/category.dart
index 19386463ba..862b2c5b38 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/category.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/category.dart
@@ -17,12 +17,12 @@ class Category {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/model/order.dart b/samples/client/petstore/dart2/openapi/lib/model/order.dart
index e9dfcfeaa9..42dc28f0fa 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/order.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/order.dart
@@ -26,17 +26,17 @@ class Order {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['petId'] == null) {
       petId = null;
     } else {
-          petId = json['petId'];
+      petId = json['petId'];
     }
     if (json['quantity'] == null) {
       quantity = null;
     } else {
-          quantity = json['quantity'];
+      quantity = json['quantity'];
     }
     if (json['shipDate'] == null) {
       shipDate = null;
@@ -46,12 +46,12 @@ class Order {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
     if (json['complete'] == null) {
       complete = null;
     } else {
-          complete = json['complete'];
+      complete = json['complete'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/model/pet.dart b/samples/client/petstore/dart2/openapi/lib/model/pet.dart
index 73407dc7dd..f7747b01cf 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/pet.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/pet.dart
@@ -26,7 +26,7 @@ class Pet {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['category'] == null) {
       category = null;
@@ -36,12 +36,12 @@ class Pet {
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
     if (json['photoUrls'] == null) {
       photoUrls = null;
     } else {
-      photoUrls = (json['photoUrls'] as List).cast<String>();
+      photoUrls = ((json['photoUrls'] ?? []) as List).map((item) => item as String).toList();
     }
     if (json['tags'] == null) {
       tags = null;
@@ -51,7 +51,7 @@ class Pet {
     if (json['status'] == null) {
       status = null;
     } else {
-          status = json['status'];
+      status = json['status'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/model/tag.dart b/samples/client/petstore/dart2/openapi/lib/model/tag.dart
index 7bd96004c2..964fa48e0e 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/tag.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/tag.dart
@@ -17,12 +17,12 @@ class Tag {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['name'] == null) {
       name = null;
     } else {
-          name = json['name'];
+      name = json['name'];
     }
   }
 
diff --git a/samples/client/petstore/dart2/openapi/lib/model/user.dart b/samples/client/petstore/dart2/openapi/lib/model/user.dart
index 0178b53944..067ce8f5c8 100644
--- a/samples/client/petstore/dart2/openapi/lib/model/user.dart
+++ b/samples/client/petstore/dart2/openapi/lib/model/user.dart
@@ -29,42 +29,42 @@ class User {
     if (json['id'] == null) {
       id = null;
     } else {
-          id = json['id'];
+      id = json['id'];
     }
     if (json['username'] == null) {
       username = null;
     } else {
-          username = json['username'];
+      username = json['username'];
     }
     if (json['firstName'] == null) {
       firstName = null;
     } else {
-          firstName = json['firstName'];
+      firstName = json['firstName'];
     }
     if (json['lastName'] == null) {
       lastName = null;
     } else {
-          lastName = json['lastName'];
+      lastName = json['lastName'];
     }
     if (json['email'] == null) {
       email = null;
     } else {
-          email = json['email'];
+      email = json['email'];
     }
     if (json['password'] == null) {
       password = null;
     } else {
-          password = json['password'];
+      password = json['password'];
     }
     if (json['phone'] == null) {
       phone = null;
     } else {
-          phone = json['phone'];
+      phone = json['phone'];
     }
     if (json['userStatus'] == null) {
       userStatus = null;
     } else {
-          userStatus = json['userStatus'];
+      userStatus = json['userStatus'];
     }
   }