diff --git a/modules/swagger-codegen/src/main/resources/scala/api.mustache b/modules/swagger-codegen/src/main/resources/scala/api.mustache
index 584441ee14e..ce927fa304e 100644
--- a/modules/swagger-codegen/src/main/resources/scala/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/scala/api.mustache
@@ -31,7 +31,7 @@ class {{classname}}(val defBasePath: String = "{{basePath}}",
 {{#allParams}}   * @param {{paramName}} {{description}} {{^required}}(optional{{#defaultValue}}, default to {{{.}}}{{/defaultValue}}){{/required}}
 {{/allParams}}   * @return {{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}void{{/returnType}}
    */
-  def {{operationId}} ({{#allParams}}{{paramName}}: {{dataType}}{{#defaultValue}} /* = {{{defaultValue}}} */{{/defaultValue}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) {{#returnType}}: Option[{{returnType}}]{{/returnType}} = {
+  def {{operationId}}({{#allParams}}{{paramName}}: {{#required}}{{dataType}}{{#defaultValue}} /* = {{{defaultValue}}}*/{{/defaultValue}}{{/required}}{{^required}}Option[{{dataType}}]{{#defaultValue}} /* = {{{defaultValue}}}*/{{/defaultValue}}{{^defaultValue}} = None{{/defaultValue}}{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}: Option[{{returnType}}]{{/returnType}} = {
     // create path and map variables
     val path = "{{path}}".replaceAll("\\{format\\}","json"){{#pathParams}}.replaceAll("\\{" + "{{baseName}}" + "\\}",apiInvoker.escape({{paramName}}))
 
@@ -53,27 +53,57 @@ class {{classname}}(val defBasePath: String = "{{basePath}}",
     {{/isPrimitiveType}}
     {{/required}}
     {{/allParams}}
-    {{#queryParams}}if(String.valueOf({{paramName}}) != "null") queryParams += "{{baseName}}" -> {{paramName}}.toString
+    {{#queryParams}}
+    {{#required}}
+    if(String.valueOf({{paramName}}) != "null") queryParams += "{{baseName}}" -> {{paramName}}.toString
+    {{/required}}
+    {{^required}}
+    {{paramName}}.map(paramVal => queryParams += "{{baseName}}" -> paramVal.toString)
+    {{/required}}
     {{/queryParams}}
     
-    {{#headerParams}}headerParams += "{{baseName}}" -> {{paramName}}
+    {{#headerParams}}
+    {{#required}}
+    headerParams += "{{baseName}}" -> {{paramName}}
+    {{/required}}
+    {{^required}}
+    {{paramName}}.map(paramVal => headerParams += "{{baseName}}" -> paramVal)
+    {{/required}}
     {{/headerParams}}
 
-    var postBody: AnyRef = {{#bodyParam}}{{paramName}}{{/bodyParam}}{{^bodyParam}}null{{/bodyParam}}
+    var postBody: AnyRef = {{#bodyParam}}{{#required}}{{paramName}}{{/required}}{{^required}}{{paramName}}.map(paramVal => paramVal){{/required}}{{/bodyParam}}{{^bodyParam}}null{{/bodyParam}}
 
     if(contentType.startsWith("multipart/form-data")) {
       val mp = new FormDataMultiPart()
       {{#formParams}}{{#notFile}}
+      {{#required}}
       mp.field("{{baseName}}", {{paramName}}.toString(), MediaType.MULTIPART_FORM_DATA_TYPE)
+      {{/required}}
+      {{^required}}
+      {{paramName}}.map(paramVal => mp.field("{{baseName}}", paramVal.toString, MediaType.MULTIPART_FORM_DATA_TYPE))
+      {{/required}}
       {{/notFile}}{{#isFile}}
+      {{#required}}
       mp.field("{{baseName}}", file.getName)
       mp.bodyPart(new FileDataBodyPart("{{baseName}}", {{paramName}}, MediaType.MULTIPART_FORM_DATA_TYPE))
+      {{/required}}
+      {{^required}}
+      file.map(fileVal => mp.field("{{baseName}}", fileVal.getName))
+      {{paramName}}.map(paramVal => mp.bodyPart(new FileDataBodyPart("{{baseName}}", paramVal, MediaType.MULTIPART_FORM_DATA_TYPE)))
+      {{/required}}
       {{/isFile}}{{/formParams}}
       postBody = mp
     }
     else {
       {{#formParams}}
-      {{#notFile}}formParams += "{{baseName}}" -> {{paramName}}.toString(){{/notFile}}
+      {{#notFile}}
+      {{#required}}
+      formParams += "{{baseName}}" -> {{paramName}}.toString()
+      {{/required}}
+      {{^required}}
+      {{paramName}}.map(paramVal => formParams += "{{baseName}}" -> paramVal.toString)
+      {{/required}}
+      {{/notFile}}
       {{/formParams}}
     }
 
diff --git a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/PetApi.scala b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/PetApi.scala
index 66ff610e9b3..52974fb7e86 100644
--- a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/PetApi.scala
+++ b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/PetApi.scala
@@ -25,8 +25,8 @@
 package io.swagger.client.api
 
 import io.swagger.client.model.Pet
-import io.swagger.client.model.ApiResponse
 import java.io.File
+import io.swagger.client.model.ApiResponse
 import io.swagger.client.ApiInvoker
 import io.swagger.client.ApiException
 
@@ -53,7 +53,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body Pet object that needs to be added to the store 
    * @return void
    */
-  def addPet (body: Pet)  = {
+  def addPet(body: Pet) = {
     // create path and map variables
     val path = "/pet".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json", "application/xml", "application/json")
@@ -66,8 +66,8 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling PetApi->addPet")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -96,7 +96,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param apiKey  (optional)
    * @return void
    */
-  def deletePet (petId: Long, apiKey: String)  = {
+  def deletePet(petId: Long, apiKey: Option[String] = None) = {
     // create path and map variables
     val path = "/pet/{petId}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "petId" + "\\}",apiInvoker.escape(petId))
 
@@ -109,8 +109,8 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
-    headerParams += "api_key" -> apiKey
+    
+    apiKey.map(paramVal => headerParams += "api_key" -> paramVal)
 
     var postBody: AnyRef = null
 
@@ -139,7 +139,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param status Status values that need to be considered for filter 
    * @return List[Pet]
    */
-  def findPetsByStatus (status: List[String]) : Option[List[Pet]] = {
+  def findPetsByStatus(status: List[String]): Option[List[Pet]] = {
     // create path and map variables
     val path = "/pet/findByStatus".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -154,7 +154,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if(String.valueOf(status) != "null") queryParams += "status" -> status.toString
     
-    
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -183,7 +183,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param tags Tags to filter by 
    * @return List[Pet]
    */
-  def findPetsByTags (tags: List[String]) : Option[List[Pet]] = {
+  def findPetsByTags(tags: List[String]): Option[List[Pet]] = {
     // create path and map variables
     val path = "/pet/findByTags".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -198,7 +198,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if(String.valueOf(tags) != "null") queryParams += "tags" -> tags.toString
     
-    
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -227,7 +227,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param petId ID of pet to return 
    * @return Pet
    */
-  def getPetById (petId: Long) : Option[Pet] = {
+  def getPetById(petId: Long): Option[Pet] = {
     // create path and map variables
     val path = "/pet/{petId}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "petId" + "\\}",apiInvoker.escape(petId))
 
@@ -240,8 +240,8 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -270,7 +270,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body Pet object that needs to be added to the store 
    * @return void
    */
-  def updatePet (body: Pet)  = {
+  def updatePet(body: Pet) = {
     // create path and map variables
     val path = "/pet".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json", "application/xml", "application/json")
@@ -283,8 +283,8 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling PetApi->updatePet")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -314,7 +314,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param status Updated status of the pet (optional)
    * @return void
    */
-  def updatePetWithForm (petId: Long, name: String, status: String)  = {
+  def updatePetWithForm(petId: Long, name: Option[String] = None, status: Option[String] = None) = {
     // create path and map variables
     val path = "/pet/{petId}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "petId" + "\\}",apiInvoker.escape(petId))
 
@@ -327,22 +327,22 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
       val mp = new FormDataMultiPart()
       
-      mp.field("name", name.toString(), MediaType.MULTIPART_FORM_DATA_TYPE)
+      name.map(paramVal => mp.field("name", paramVal.toString, MediaType.MULTIPART_FORM_DATA_TYPE))
       
-      mp.field("status", status.toString(), MediaType.MULTIPART_FORM_DATA_TYPE)
+      status.map(paramVal => mp.field("status", paramVal.toString, MediaType.MULTIPART_FORM_DATA_TYPE))
       
       postBody = mp
     }
     else {
-      formParams += "name" -> name.toString()
-      formParams += "status" -> status.toString()
+      name.map(paramVal => formParams += "name" -> paramVal.toString)
+      status.map(paramVal => formParams += "status" -> paramVal.toString)
     }
 
     try {
@@ -364,7 +364,7 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param file file to upload (optional)
    * @return ApiResponse
    */
-  def uploadFile (petId: Long, additionalMetadata: String, file: File) : Option[ApiResponse] = {
+  def uploadFile(petId: Long, additionalMetadata: Option[String] = None, file: Option[File] = None): Option[ApiResponse] = {
     // create path and map variables
     val path = "/pet/{petId}/uploadImage".replaceAll("\\{format\\}","json").replaceAll("\\{" + "petId" + "\\}",apiInvoker.escape(petId))
 
@@ -377,23 +377,22 @@ class PetApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
       val mp = new FormDataMultiPart()
       
-      mp.field("additionalMetadata", additionalMetadata.toString(), MediaType.MULTIPART_FORM_DATA_TYPE)
+      additionalMetadata.map(paramVal => mp.field("additionalMetadata", paramVal.toString, MediaType.MULTIPART_FORM_DATA_TYPE))
       
-      mp.field("file", file.getName)
-      mp.bodyPart(new FileDataBodyPart("file", file, MediaType.MULTIPART_FORM_DATA_TYPE))
+      file.map(fileVal => mp.field("file", fileVal.getName))
+      file.map(paramVal => mp.bodyPart(new FileDataBodyPart("file", paramVal, MediaType.MULTIPART_FORM_DATA_TYPE)))
       
       postBody = mp
     }
     else {
-      formParams += "additionalMetadata" -> additionalMetadata.toString()
-      
+      additionalMetadata.map(paramVal => formParams += "additionalMetadata" -> paramVal.toString)
     }
 
     try {
diff --git a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/StoreApi.scala b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/StoreApi.scala
index 2d184550d13..94052904927 100644
--- a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/StoreApi.scala
+++ b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/StoreApi.scala
@@ -51,7 +51,7 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param orderId ID of the order that needs to be deleted 
    * @return void
    */
-  def deleteOrder (orderId: String)  = {
+  def deleteOrder(orderId: String) = {
     // create path and map variables
     val path = "/store/order/{orderId}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "orderId" + "\\}",apiInvoker.escape(orderId))
 
@@ -64,8 +64,8 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -92,7 +92,7 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * Returns a map of status codes to quantities
    * @return Map[String, Integer]
    */
-  def getInventory () : Option[Map[String, Integer]] = {
+  def getInventory(): Option[Map[String, Integer]] = {
     // create path and map variables
     val path = "/store/inventory".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -103,8 +103,8 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -133,7 +133,7 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param orderId ID of pet that needs to be fetched 
    * @return Order
    */
-  def getOrderById (orderId: Long) : Option[Order] = {
+  def getOrderById(orderId: Long): Option[Order] = {
     // create path and map variables
     val path = "/store/order/{orderId}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "orderId" + "\\}",apiInvoker.escape(orderId))
 
@@ -146,8 +146,8 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -176,7 +176,7 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body order placed for purchasing the pet 
    * @return Order
    */
-  def placeOrder (body: Order) : Option[Order] = {
+  def placeOrder(body: Order): Option[Order] = {
     // create path and map variables
     val path = "/store/order".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -189,8 +189,8 @@ class StoreApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling StoreApi->placeOrder")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
diff --git a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/UserApi.scala b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/UserApi.scala
index db6ada19ebc..d996b7f4f16 100644
--- a/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/UserApi.scala
+++ b/samples/client/petstore/scala/src/main/scala/io/swagger/client/api/UserApi.scala
@@ -51,7 +51,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body Created user object 
    * @return void
    */
-  def createUser (body: User)  = {
+  def createUser(body: User) = {
     // create path and map variables
     val path = "/user".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -64,8 +64,8 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling UserApi->createUser")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -93,7 +93,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body List of user object 
    * @return void
    */
-  def createUsersWithArrayInput (body: List[User])  = {
+  def createUsersWithArrayInput(body: List[User]) = {
     // create path and map variables
     val path = "/user/createWithArray".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -106,8 +106,8 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling UserApi->createUsersWithArrayInput")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -135,7 +135,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param body List of user object 
    * @return void
    */
-  def createUsersWithListInput (body: List[User])  = {
+  def createUsersWithListInput(body: List[User]) = {
     // create path and map variables
     val path = "/user/createWithList".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -148,8 +148,8 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling UserApi->createUsersWithListInput")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -177,7 +177,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param username The name that needs to be deleted 
    * @return void
    */
-  def deleteUser (username: String)  = {
+  def deleteUser(username: String) = {
     // create path and map variables
     val path = "/user/{username}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "username" + "\\}",apiInvoker.escape(username))
 
@@ -190,8 +190,8 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -219,7 +219,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param username The name that needs to be fetched. Use user1 for testing.  
    * @return User
    */
-  def getUserByName (username: String) : Option[User] = {
+  def getUserByName(username: String): Option[User] = {
     // create path and map variables
     val path = "/user/{username}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "username" + "\\}",apiInvoker.escape(username))
 
@@ -232,8 +232,8 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -263,7 +263,7 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
    * @param password The password for login in clear text 
    * @return String
    */
-  def loginUser (username: String, password: String) : Option[String] = {
+  def loginUser(username: String, password: String): Option[String] = {
     // create path and map variables
     val path = "/user/login".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -275,9 +275,9 @@ class UserApi(val defBasePath: String = "http://petstore.swagger.io/v2",
     val formParams = new HashMap[String, String]
 
     if(String.valueOf(username) != "null") queryParams += "username" -> username.toString
-if(String.valueOf(password) != "null") queryParams += "password" -> password.toString
-    
+    if(String.valueOf(password) != "null") queryParams += "password" -> password.toString
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -305,7 +305,7 @@ if(String.valueOf(password) != "null") queryParams += "password" -> password.toS
    * 
    * @return void
    */
-  def logoutUser ()  = {
+  def logoutUser() = {
     // create path and map variables
     val path = "/user/logout".replaceAll("\\{format\\}","json")
     val contentTypes = List("application/json")
@@ -316,8 +316,8 @@ if(String.valueOf(password) != "null") queryParams += "password" -> password.toS
     val headerParams = new HashMap[String, String]
     val formParams = new HashMap[String, String]
 
-        
     
+
     var postBody: AnyRef = null
 
     if(contentType.startsWith("multipart/form-data")) {
@@ -346,7 +346,7 @@ if(String.valueOf(password) != "null") queryParams += "password" -> password.toS
    * @param body Updated user object 
    * @return void
    */
-  def updateUser (username: String, body: User)  = {
+  def updateUser(username: String, body: User) = {
     // create path and map variables
     val path = "/user/{username}".replaceAll("\\{format\\}","json").replaceAll("\\{" + "username" + "\\}",apiInvoker.escape(username))
 
@@ -361,8 +361,8 @@ if(String.valueOf(password) != "null") queryParams += "password" -> password.toS
 
     if (body == null) throw new Exception("Missing required parameter 'body' when calling UserApi->updateUser")
 
-        
     
+
     var postBody: AnyRef = body
 
     if(contentType.startsWith("multipart/form-data")) {