diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
index 34deb0b0fca7..ef72bae11fd3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
@@ -81,8 +81,6 @@ public CppPistacheServerCodegen() {
 
         reservedWords = new HashSet<>();
 
-        supportingFiles.add(new SupportingFile("modelbase-header.mustache", "model", modelNamePrefix + "ModelBase.h"));
-        supportingFiles.add(new SupportingFile("modelbase-source.mustache", "model", modelNamePrefix + "ModelBase.cpp"));
         supportingFiles.add(new SupportingFile("helpers-header.mustache", "model", modelNamePrefix + "Helpers.h"));
         supportingFiles.add(new SupportingFile("helpers-source.mustache", "model", modelNamePrefix + "Helpers.cpp"));
         supportingFiles.add(new SupportingFile("main-api-server.mustache", "", modelNamePrefix + "main-api-server.cpp"));
@@ -124,8 +122,6 @@ public void processOpts() {
         if (additionalProperties.containsKey("modelNamePrefix")) {
             additionalProperties().put("prefix", modelNamePrefix);
             supportingFiles.clear();
-            supportingFiles.add(new SupportingFile("modelbase-header.mustache", "model", modelNamePrefix + "ModelBase.h"));
-            supportingFiles.add(new SupportingFile("modelbase-source.mustache", "model", modelNamePrefix + "ModelBase.cpp"));
             supportingFiles.add(new SupportingFile("helpers-header.mustache", "model", modelNamePrefix + "Helpers.h"));
             supportingFiles.add(new SupportingFile("helpers-source.mustache", "model", modelNamePrefix + "Helpers.cpp"));
             supportingFiles.add(new SupportingFile("main-api-server.mustache", "", modelNamePrefix + "main-api-server.cpp"));
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/README.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/README.mustache
index e6e1a0b2883d..c568d8316d49 100644
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/README.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-pistache-server/README.mustache
@@ -41,7 +41,7 @@ cd build
 ## Libraries required
 - [pistache](http://pistache.io/quickstart)
 - [JSON for Modern C++](https://github.com/nlohmann/json/#integration): Please download the `json.hpp` file and
-put it under the model folder
+put it under the model/nlohmann folder
 
 ## Namespaces
 {{{apiPackage}}}
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/api-source.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/api-source.mustache
index f1a7841c4020..c529fbea5799 100644
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/api-source.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-pistache-server/api-source.mustache
@@ -70,14 +70,7 @@ void {{classname}}::{{operationIdSnakeCase}}_handler(const Pistache::Rest::Reque
     try {
     {{#hasBodyParam}}
     {{#bodyParam}}
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    {{^isPrimitiveType}}{{^isContainer}}
-      {{paramName}}.fromJson(request_body);
-    {{/isContainer}}{{/isPrimitiveType}}{{#isContainer}}  {{paramName}} = {{#isListContainer}}  {{prefix}}ArrayHelper{{/isListContainer}}{{#isMapContainer}}  {{prefix}}MapHelper{{/isMapContainer}}::fromJson<{{items.baseType}}>(request_body);{{/isContainer}}
-    {{#isPrimitiveType}}
-      // The conversion is done automatically by the json library
-      {{paramName}} = request_body;
-    {{/isPrimitiveType}}
+      nlohmann::json::parse(request.body()).get_to({{paramName}});
     {{/bodyParam}}
     {{/hasBodyParam}}
       this->{{operationIdSnakeCase}}({{#allParams}}{{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}}{{#hasParams}}, {{/hasParams}}response);
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/cmake.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/cmake.mustache
index 115fac401ca0..a822ae28ae59 100644
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/cmake.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-pistache-server/cmake.mustache
@@ -20,7 +20,6 @@ ExternalProject_Add(NLOHMANN
 
 )
 include_directories(${EXTERNAL_INSTALL_LOCATION}/include)
-include_directories(${EXTERNAL_INSTALL_LOCATION}/include/nlohmann)
 link_directories(${EXTERNAL_INSTALL_LOCATION}/lib)
 {{/addExternalLibs}}
 
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-header.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-header.mustache
index b297ab131dbc..a05667766a9f 100644
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-header.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-header.mustache
@@ -9,10 +9,9 @@
 #define {{classname}}_H_
 
 {{{defaultInclude}}}
-#include "{{prefix}}ModelBase.h"
-
 {{#imports}}{{{this}}}
 {{/imports}}
+#include <nlohmann/json.hpp>
 
 {{#modelNamespaceDeclarations}}
 namespace {{this}} {
@@ -22,19 +21,12 @@ namespace {{this}} {
 /// {{description}}
 /// </summary>
 class {{declspec}} {{classname}}
-    : public {{prefix}}ModelBase
 {
 public:
     {{classname}}();
     virtual ~{{classname}}();
 
-    /////////////////////////////////////////////
-    /// {{prefix}}ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// {{classname}} members
@@ -51,6 +43,8 @@ public:
     {{/required}}
     {{/vars}}
 
+    friend void to_json(nlohmann::json& j, const {{classname}}& o);
+    friend void from_json(const nlohmann::json& j, {{classname}}& o);
 protected:
     {{#vars}}
     {{{dataType}}} m_{{name}};
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-source.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-source.mustache
index 5ad0ef24006e..e6cf11ea5273 100644
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-source.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-pistache-server/model-source.mustache
@@ -25,126 +25,26 @@ void {{classname}}::validate()
     // TODO: implement validation
 }
 
-nlohmann::json {{classname}}::toJson() const
+void to_json(nlohmann::json& j, const {{classname}}& o)
 {
-    nlohmann::json val = nlohmann::json::object();
-
-    {{#vars}}{{#isPrimitiveType}}{{^isListContainer}}{{^required}}if(m_{{name}}IsSet)
-    {
-        val["{{baseName}}"] = m_{{name}};
-    }
-    {{/required}}{{#required}}val["{{baseName}}"] = m_{{name}};
-    {{/required}}{{/isListContainer}}{{/isPrimitiveType}}{{#isListContainer}}{
-        nlohmann::json jsonArray;
-        for( const auto& item : m_{{name}} )
-        {
-            jsonArray.push_back({{prefix}}ModelBase::toJson(item));
-        }
-        {{#required}}val["{{baseName}}"] = jsonArray;
-        {{/required}}{{^required}}
-        if(jsonArray.size() > 0)
-        {
-            val["{{baseName}}"] = jsonArray;
-        } {{/required}}
-    }
-    {{/isListContainer}}{{#isMapContainer}}{
-        nlohmann::json jsonObj;
-        for( const auto& item : m_{{name}} )
-        {   {{^items.isContainer}} 
-            jsonObj[item.first] = {{prefix}}ModelBase::toJson(item.second);{{/items.isContainer}} {{#items.isListContainer}} 
-            jsonObj[item.first] = {{prefix}}ArrayHelper::toJson<{{{items.items.datatype}}}>(item.second);
-            {{/items.isListContainer}} {{#items.isMapContainer}} 
-            jsonObj[item.first] = {{prefix}}MapHelper::toJson<{{{items.items.datatype}}}>(item.second); {{/items.isMapContainer}} 
-        }
-        {{#required}}val["{{baseName}}"] = jsonObj; {{/required}}{{^required}}
-        if(jsonObj.size() > 0)
-        {
-            val["{{baseName}}"] = jsonObj;
-        } {{/required}}
-    }
-    {{/isMapContainer}}{{^isContainer}}{{^isPrimitiveType}}{{^required}}if(m_{{name}}IsSet)
-    {
-        val["{{baseName}}"] = {{prefix}}ModelBase::toJson(m_{{name}});
-    }
-    {{/required}}{{#required}}val["{{baseName}}"] = {{prefix}}ModelBase::toJson(m_{{name}});
-    {{/required}}{{/isPrimitiveType}}{{/isContainer}}{{/vars}}
-
-    return val;
+    j = nlohmann::json();
+    {{#vars}}
+    {{#required}}j["{{baseName}}"] = o.m_{{name}};{{/required}}{{^required}}if(o.{{nameInCamelCase}}IsSet())
+        j["{{baseName}}"] = o.m_{{name}};{{/required}}
+    {{/vars}}
 }
 
-void {{classname}}::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, {{classname}}& o)
 {
-    {{#vars}}{{#isPrimitiveType}}{{^isListContainer}}{{^required}}if(val.find("{{baseName}}") != val.end())
-    {
-        {{setter}}(val.at("{{baseName}}"));
-    }
-    {{/required}}{{#required}}{{setter}}(val.at("{{baseName}}"));
-    {{/required}}{{/isListContainer}}{{/isPrimitiveType}}{{#isListContainer}}{
-        m_{{name}}.clear();
-        {{^required}}if(val.find("{{baseName}}") != val.end())
-        {
-        {{/required}}
-            for( const auto& item : val["{{baseName}}"] )
-            {
-                {{#isPrimitiveType}}m_{{name}}.push_back(item);
-                {{/isPrimitiveType}}{{^isPrimitiveType}}{{#items.isString}}m_{{name}}.push_back(item);
-                {{/items.isString}}{{^items.isString}}{{#items.isDateTime}}m_{{name}}.push_back(item);
-                {{/items.isDateTime}}{{^items.isDateTime}}
-                if(item.is_null())
-                {
-                    m_{{name}}.push_back( {{{items.datatype}}}() );
-                }
-                else
-                {
-                    {{{items.datatype}}} newItem;
-                    newItem.fromJson(item);
-                    m_{{name}}.push_back( newItem );
-                }
-                {{/items.isDateTime}}{{/items.isString}}{{/isPrimitiveType}}
-            }
-        {{^required}}
-        }
-        {{/required}}
-    }
-    {{/isListContainer}}{{#isMapContainer}}{
-        m_{{name}}.clear();
-        {{^required}}if(val.find("{{baseName}}") != val.end())
-        {
-        {{/required}}
-            if(val["{{baseName}}"].is_object()) { {{^items.isContainer}}
-                m_{{name}} = {{prefix}}MapHelper::fromJson<{{{items.datatype}}}>(val["{{baseName}}"]);
-                {{/items.isContainer}} {{#items.isContainer}}
-                for( const auto& item : val["{{baseName}}"].items() )
-                {   {{#items.isMapContainer}}
-                    {{{items.datatype}}} newItem = {{prefix}}MapHelper::fromJson<{{{items.items.datatype}}}>(item.value());
-                    {{/items.isMapContainer}}{{#items.isListContainer}} 
-                    {{{items.datatype}}} newItem = {{prefix}}ArrayHelper::fromJson<{{{items.items.datatype}}}>(item.value());
-                    {{/items.isListContainer}}
-                    m_{{name}}.insert(m_{{name}}.end(), std::pair< std::string, {{{items.datatype}}} >(item.key(), newItem));
-                } {{/items.isContainer}}
-            }
-        {{^required}}
-        }
-        {{/required}}
-    }
-    {{/isMapContainer}}{{^isContainer}}{{^isPrimitiveType}}{{^required}}if(val.find("{{baseName}}") != val.end())
+    {{#vars}}
+    {{#required}}j.at("{{baseName}}").get_to(o.m_{{name}});{{/required}}{{^required}}if(!j.at("{{baseName}}").is_null())
     {
-        {{#isString}}{{setter}}(val.at("{{baseName}}"));{{/isString}}{{#isByteArray}}{{setter}}(val.at("{{baseName}}"));{{/isByteArray}}{{#isBinary}}{{setter}}(val.at("{{baseName}}"));
-        {{/isBinary}}{{^isString}}{{#isDateTime}}{{setter}}(val.at("{{baseName}}"));
-        {{/isDateTime}}{{^isDateTime}}{{^isByteArray}}{{^isBinary}}if(!val["{{baseName}}"].is_null())
-        {
-            {{{dataType}}} newItem;
-            newItem.fromJson(val["{{baseName}}"]);
-            {{setter}}( newItem );
-        }
-        {{/isBinary}}{{/isByteArray}}{{/isDateTime}}{{/isString}}
-    }
-    {{/required}}{{#required}}{{#isString}}{{setter}}(val.at("{{baseName}}"));
-    {{/isString}}{{^isString}}{{#isDateTime}}{{setter}}(val.at("{{baseName}}"));
-    {{/isDateTime}}{{/isString}}{{/required}}{{/isPrimitiveType}}{{/isContainer}}{{/vars}}
+        j.at("{{baseName}}").get_to(o.m_{{name}});
+        o.m_{{name}}IsSet = true;
+    } {{/required}}
+    {{/vars}}
 }
 
-
 {{#vars}}{{#isContainer}}{{{dataType}}}& {{classname}}::{{getter}}()
 {
     return m_{{name}};
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-header.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-header.mustache
deleted file mode 100644
index 8840764a57a2..000000000000
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-header.mustache
+++ /dev/null
@@ -1,127 +0,0 @@
-{{>licenseInfo}}
-/*
- * {{prefix}}ModelBase.h
- *
- * This is the base class for all model classes
- */
-
-#ifndef {{prefix}}ModelBase_H_
-#define {{prefix}}ModelBase_H_
-
-{{{defaultInclude}}}
-#include "json.hpp"
-#include <ctime>
-#include <string>
-#include <vector>
-#include <map>
-
-{{#modelNamespaceDeclarations}}
-namespace {{this}} {
-{{/modelNamespaceDeclarations}}
-
-class {{declspec}} {{prefix}}ModelBase
-{
-public:
-    {{prefix}}ModelBase();
-    virtual ~{{prefix}}ModelBase();
-
-    virtual void validate() = 0;
-
-    virtual nlohmann::json toJson() const = 0;
-    virtual void fromJson(const nlohmann::json& json) = 0;
-
-    static std::string toJson(  std::string const& value );
-    static std::string toJson(  std::time_t const& value );
-    static int32_t toJson( int32_t const value );
-    static int64_t toJson( int64_t const value );
-    static double toJson( double const value );
-    static bool toJson( bool const value );
-    static nlohmann::json toJson({{prefix}}ModelBase const& content ); 
-};
-
-class {{prefix}}ArrayHelper {
-private:
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static void itemFromJson(T& item, const nlohmann::json& json){
-        item = json;
-    }
-    static void itemFromJson(ModelBase& item, const nlohmann::json& json){
-        item.fromJson(json);
-    }
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static nlohmann::json itemtoJson(const T& item){
-        return item;
-    }
-    static nlohmann::json itemtoJson(const ModelBase& item){
-        return item.toJson();
-    }
-public:
-    template<typename T>
-    static std::vector<T> fromJson(const nlohmann::json& json) {
-        std::vector<T> val;
-        if (!json.empty()) {
-            for (const auto& item : json.items()) {
-                T entry;
-                itemFromJson(entry, item.value());
-                val.push_back(entry);
-            }
-        }
-        return val;
-    }
-    template<typename T>
-    static nlohmann::json toJson(const std::vector<T>& val) {
-        nlohmann::json json;
-        for(const auto& item : val){
-            json.push_back(itemtoJson(item));
-        }
-        return json;
-    }
-};
-
-class {{prefix}}MapHelper {
-private:
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static void itemFromJson(T &item, const nlohmann::json& json){
-        item = json;
-    }
-    static void itemFromJson(ModelBase &item, const nlohmann::json& json){
-        item.fromJson(json);
-    }
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static nlohmann::json itemtoJson(const T& item){
-        return item;
-    }
-    static nlohmann::json itemtoJson(const ModelBase& item){
-        return item.toJson();
-    }
-
-public:
-    template<typename T>
-    static std::map<std::string, T> fromJson(const nlohmann::json& json) {
-        std::map<std::string, T> val;
-        if (!json.empty()) {
-            for (const auto& item : json.items()) {
-                T entry;
-                itemfromJson(entry, item.value());
-                val.insert(val.end(),
-                        std::pair<std::string, T>(item.key(), entry));
-            }
-        }
-        return val;
-    }
-    template<typename T>
-    static nlohmann::json toJson(const std::map<std::string, T>& val) {
-        nlohmann::json json;
-        for (const auto& item : val) {
-          nlohmann::json jitem = itemtoJson(item.second);
-          json[item.first] = jitem;
-        }
-        return json;
-    }
-};
-
-{{#modelNamespaceDeclarations}}
-}
-{{/modelNamespaceDeclarations}}
-
-#endif /* {{prefix}}ModelBase_H_ */
diff --git a/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-source.mustache b/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-source.mustache
deleted file mode 100644
index f097c3a4a199..000000000000
--- a/modules/openapi-generator/src/main/resources/cpp-pistache-server/modelbase-source.mustache
+++ /dev/null
@@ -1,54 +0,0 @@
-{{>licenseInfo}}
-#include "{{prefix}}ModelBase.h"
-
-{{#modelNamespaceDeclarations}}
-namespace {{this}} {
-{{/modelNamespaceDeclarations}}
-
-{{prefix}}ModelBase::{{prefix}}ModelBase()
-{
-}
-{{prefix}}ModelBase::~{{prefix}}ModelBase()
-{
-}
-
-std::string {{prefix}}ModelBase::toJson( std::string const& value )
-{
-    return value;
-}
-
-std::string {{prefix}}ModelBase::toJson( std::time_t const& value )
-{
-    char buf[sizeof "2011-10-08T07:07:09Z"];
-    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&value));
-    return buf;
-}
-
-int32_t {{prefix}}ModelBase::toJson( int32_t const value )
-{
-    return value;
-}
-
-int64_t {{prefix}}ModelBase::toJson( int64_t const value )
-{
-    return value;
-}
-
-double {{prefix}}ModelBase::toJson( double const value )
-{
-    return value;
-}
-
-bool {{prefix}}ModelBase::toJson( bool const value )
-{
-    return value;
-}
-
-nlohmann::json {{prefix}}ModelBase::toJson({{prefix}}ModelBase const& content )
-{
-    return content.toJson();
-}
-
-{{#modelNamespaceDeclarations}}
-}
-{{/modelNamespaceDeclarations}}
diff --git a/samples/server/petstore/cpp-pistache/.openapi-generator/VERSION b/samples/server/petstore/cpp-pistache/.openapi-generator/VERSION
index 0f58aa041419..afa636560641 100644
--- a/samples/server/petstore/cpp-pistache/.openapi-generator/VERSION
+++ b/samples/server/petstore/cpp-pistache/.openapi-generator/VERSION
@@ -1 +1 @@
-3.1.2-SNAPSHOT
\ No newline at end of file
+4.0.0-SNAPSHOT
\ No newline at end of file
diff --git a/samples/server/petstore/cpp-pistache/CMakeLists.txt b/samples/server/petstore/cpp-pistache/CMakeLists.txt
index 278caa8ab3d2..0cd21eda2986 100644
--- a/samples/server/petstore/cpp-pistache/CMakeLists.txt
+++ b/samples/server/petstore/cpp-pistache/CMakeLists.txt
@@ -19,7 +19,6 @@ ExternalProject_Add(NLOHMANN
 
 )
 include_directories(${EXTERNAL_INSTALL_LOCATION}/include)
-include_directories(${EXTERNAL_INSTALL_LOCATION}/include/nlohmann)
 link_directories(${EXTERNAL_INSTALL_LOCATION}/lib)
 
 include_directories(model)
diff --git a/samples/server/petstore/cpp-pistache/README.md b/samples/server/petstore/cpp-pistache/README.md
index c8587ab3d706..7d4392fde7e9 100644
--- a/samples/server/petstore/cpp-pistache/README.md
+++ b/samples/server/petstore/cpp-pistache/README.md
@@ -41,7 +41,7 @@ cd build
 ## Libraries required
 - [pistache](http://pistache.io/quickstart)
 - [JSON for Modern C++](https://github.com/nlohmann/json/#integration): Please download the `json.hpp` file and
-put it under the model folder
+put it under the model/nlohmann folder
 
 ## Namespaces
 org.openapitools.server.api
diff --git a/samples/server/petstore/cpp-pistache/api/PetApi.cpp b/samples/server/petstore/cpp-pistache/api/PetApi.cpp
index c62755f78de7..5ffab955c55c 100644
--- a/samples/server/petstore/cpp-pistache/api/PetApi.cpp
+++ b/samples/server/petstore/cpp-pistache/api/PetApi.cpp
@@ -49,14 +49,11 @@ void PetApi::add_pet_handler(const Pistache::Rest::Request &request, Pistache::H
 
     // Getting the body param
     
-    Pet pet;
+    Pet body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    
-      pet.fromJson(request_body);
-    
-      this->add_pet(pet, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->add_pet(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
@@ -139,14 +136,11 @@ void PetApi::update_pet_handler(const Pistache::Rest::Request &request, Pistache
 
     // Getting the body param
     
-    Pet pet;
+    Pet body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    
-      pet.fromJson(request_body);
-    
-      this->update_pet(pet, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->update_pet(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
diff --git a/samples/server/petstore/cpp-pistache/api/PetApi.h b/samples/server/petstore/cpp-pistache/api/PetApi.h
index d34ff4afa7ef..c84ca384279e 100644
--- a/samples/server/petstore/cpp-pistache/api/PetApi.h
+++ b/samples/server/petstore/cpp-pistache/api/PetApi.h
@@ -65,8 +65,8 @@ class  PetApi {
     /// <remarks>
     /// 
     /// </remarks>
-    /// <param name="pet">Pet object that needs to be added to the store</param>
-    virtual void add_pet(const Pet &pet, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">Pet object that needs to be added to the store</param>
+    virtual void add_pet(const Pet &body, Pistache::Http::ResponseWriter &response) = 0;
 
     /// <summary>
     /// Deletes a pet
@@ -111,8 +111,8 @@ class  PetApi {
     /// <remarks>
     /// 
     /// </remarks>
-    /// <param name="pet">Pet object that needs to be added to the store</param>
-    virtual void update_pet(const Pet &pet, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">Pet object that needs to be added to the store</param>
+    virtual void update_pet(const Pet &body, Pistache::Http::ResponseWriter &response) = 0;
 
     /// <summary>
     /// Updates a pet in the store with form data
diff --git a/samples/server/petstore/cpp-pistache/api/StoreApi.cpp b/samples/server/petstore/cpp-pistache/api/StoreApi.cpp
index 58b9b28986d8..98e4d387a190 100644
--- a/samples/server/petstore/cpp-pistache/api/StoreApi.cpp
+++ b/samples/server/petstore/cpp-pistache/api/StoreApi.cpp
@@ -82,14 +82,11 @@ void StoreApi::place_order_handler(const Pistache::Rest::Request &request, Pista
 
     // Getting the body param
     
-    Order order;
+    Order body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    
-      order.fromJson(request_body);
-    
-      this->place_order(order, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->place_order(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
diff --git a/samples/server/petstore/cpp-pistache/api/StoreApi.h b/samples/server/petstore/cpp-pistache/api/StoreApi.h
index 53117f32a2e4..cde0755f1383 100644
--- a/samples/server/petstore/cpp-pistache/api/StoreApi.h
+++ b/samples/server/petstore/cpp-pistache/api/StoreApi.h
@@ -87,8 +87,8 @@ class  StoreApi {
     /// <remarks>
     /// 
     /// </remarks>
-    /// <param name="order">order placed for purchasing the pet</param>
-    virtual void place_order(const Order &order, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">order placed for purchasing the pet</param>
+    virtual void place_order(const Order &body, Pistache::Http::ResponseWriter &response) = 0;
 
 };
 
diff --git a/samples/server/petstore/cpp-pistache/api/UserApi.cpp b/samples/server/petstore/cpp-pistache/api/UserApi.cpp
index b534b87f2190..f539a61c7e96 100644
--- a/samples/server/petstore/cpp-pistache/api/UserApi.cpp
+++ b/samples/server/petstore/cpp-pistache/api/UserApi.cpp
@@ -49,14 +49,11 @@ void UserApi::create_user_handler(const Pistache::Rest::Request &request, Pistac
 
     // Getting the body param
     
-    User user;
+    User body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    
-      user.fromJson(request_body);
-    
-      this->create_user(user, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->create_user(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
@@ -67,12 +64,11 @@ void UserApi::create_user_handler(const Pistache::Rest::Request &request, Pistac
 void UserApi::create_users_with_array_input_handler(const Pistache::Rest::Request &request, Pistache::Http::ResponseWriter response) {
 
     // Getting the body param
-    std::vector<User> user;
+    std::vector<User> body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-      user =   ArrayHelper::fromJson<User>(request_body);
-      this->create_users_with_array_input(user, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->create_users_with_array_input(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
@@ -83,12 +79,11 @@ void UserApi::create_users_with_array_input_handler(const Pistache::Rest::Reques
 void UserApi::create_users_with_list_input_handler(const Pistache::Rest::Request &request, Pistache::Http::ResponseWriter response) {
 
     // Getting the body param
-    std::vector<User> user;
+    std::vector<User> body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-      user =   ArrayHelper::fromJson<User>(request_body);
-      this->create_users_with_list_input(user, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->create_users_with_list_input(body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
@@ -168,14 +163,11 @@ void UserApi::update_user_handler(const Pistache::Rest::Request &request, Pistac
     
     // Getting the body param
     
-    User user;
+    User body;
     
     try {
-      nlohmann::json request_body = nlohmann::json::parse(request.body());
-    
-      user.fromJson(request_body);
-    
-      this->update_user(username, user, response);
+      nlohmann::json::parse(request.body()).get_to(body);
+      this->update_user(username, body, response);
     } catch (std::runtime_error & e) {
       //send a 400 error
       response.send(Pistache::Http::Code::Bad_Request, e.what());
diff --git a/samples/server/petstore/cpp-pistache/api/UserApi.h b/samples/server/petstore/cpp-pistache/api/UserApi.h
index 8ec6bb5692f7..7083c7643070 100644
--- a/samples/server/petstore/cpp-pistache/api/UserApi.h
+++ b/samples/server/petstore/cpp-pistache/api/UserApi.h
@@ -65,8 +65,8 @@ class  UserApi {
     /// <remarks>
     /// This can only be done by the logged in user.
     /// </remarks>
-    /// <param name="user">Created user object</param>
-    virtual void create_user(const User &user, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">Created user object</param>
+    virtual void create_user(const User &body, Pistache::Http::ResponseWriter &response) = 0;
 
     /// <summary>
     /// Creates list of users with given input array
@@ -74,8 +74,8 @@ class  UserApi {
     /// <remarks>
     /// 
     /// </remarks>
-    /// <param name="user">List of user object</param>
-    virtual void create_users_with_array_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">List of user object</param>
+    virtual void create_users_with_array_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response) = 0;
 
     /// <summary>
     /// Creates list of users with given input array
@@ -83,8 +83,8 @@ class  UserApi {
     /// <remarks>
     /// 
     /// </remarks>
-    /// <param name="user">List of user object</param>
-    virtual void create_users_with_list_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">List of user object</param>
+    virtual void create_users_with_list_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response) = 0;
 
     /// <summary>
     /// Delete user
@@ -129,8 +129,8 @@ class  UserApi {
     /// This can only be done by the logged in user.
     /// </remarks>
     /// <param name="username">name that need to be deleted</param>
-    /// <param name="user">Updated user object</param>
-    virtual void update_user(const std::string &username, const User &user, Pistache::Http::ResponseWriter &response) = 0;
+    /// <param name="body">Updated user object</param>
+    virtual void update_user(const std::string &username, const User &body, Pistache::Http::ResponseWriter &response) = 0;
 
 };
 
diff --git a/samples/server/petstore/cpp-pistache/impl/PetApiImpl.cpp b/samples/server/petstore/cpp-pistache/impl/PetApiImpl.cpp
index 6e8801d1a30b..b35b40899b01 100644
--- a/samples/server/petstore/cpp-pistache/impl/PetApiImpl.cpp
+++ b/samples/server/petstore/cpp-pistache/impl/PetApiImpl.cpp
@@ -23,7 +23,7 @@ PetApiImpl::PetApiImpl(std::shared_ptr<Pistache::Rest::Router> rtr)
     : PetApi(rtr)
     { }
 
-void PetApiImpl::add_pet(const Pet &pet, Pistache::Http::ResponseWriter &response) {
+void PetApiImpl::add_pet(const Pet &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
 void PetApiImpl::delete_pet(const int64_t &petId, const Pistache::Optional<Pistache::Http::Header::Raw> &apiKey, Pistache::Http::ResponseWriter &response) {
@@ -38,7 +38,7 @@ void PetApiImpl::find_pets_by_tags(const Pistache::Optional<std::vector<std::str
 void PetApiImpl::get_pet_by_id(const int64_t &petId, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
-void PetApiImpl::update_pet(const Pet &pet, Pistache::Http::ResponseWriter &response) {
+void PetApiImpl::update_pet(const Pet &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
 void PetApiImpl::update_pet_with_form(const Pistache::Rest::Request &request, Pistache::Http::ResponseWriter &response){
diff --git a/samples/server/petstore/cpp-pistache/impl/PetApiImpl.h b/samples/server/petstore/cpp-pistache/impl/PetApiImpl.h
index 3cca98421fdb..7b4f3d324050 100644
--- a/samples/server/petstore/cpp-pistache/impl/PetApiImpl.h
+++ b/samples/server/petstore/cpp-pistache/impl/PetApiImpl.h
@@ -45,12 +45,12 @@ class PetApiImpl : public org::openapitools::server::api::PetApi {
     PetApiImpl(std::shared_ptr<Pistache::Rest::Router>);
     ~PetApiImpl() {}
 
-    void add_pet(const Pet &pet, Pistache::Http::ResponseWriter &response);
+    void add_pet(const Pet &body, Pistache::Http::ResponseWriter &response);
     void delete_pet(const int64_t &petId, const Pistache::Optional<Pistache::Http::Header::Raw> &apiKey, Pistache::Http::ResponseWriter &response);
     void find_pets_by_status(const Pistache::Optional<std::vector<std::string>> &status, Pistache::Http::ResponseWriter &response);
     void find_pets_by_tags(const Pistache::Optional<std::vector<std::string>> &tags, Pistache::Http::ResponseWriter &response);
     void get_pet_by_id(const int64_t &petId, Pistache::Http::ResponseWriter &response);
-    void update_pet(const Pet &pet, Pistache::Http::ResponseWriter &response);
+    void update_pet(const Pet &body, Pistache::Http::ResponseWriter &response);
     void update_pet_with_form(const Pistache::Rest::Request &request, Pistache::Http::ResponseWriter &response);
     void upload_file(const Pistache::Rest::Request &request, Pistache::Http::ResponseWriter &response);
 
diff --git a/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.cpp b/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.cpp
index f5367c72b7f9..63030737b61e 100644
--- a/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.cpp
+++ b/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.cpp
@@ -32,7 +32,7 @@ void StoreApiImpl::get_inventory(Pistache::Http::ResponseWriter &response) {
 void StoreApiImpl::get_order_by_id(const int64_t &orderId, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
-void StoreApiImpl::place_order(const Order &order, Pistache::Http::ResponseWriter &response) {
+void StoreApiImpl::place_order(const Order &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
 
diff --git a/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.h b/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.h
index d28acea1f670..71689ae18b1d 100644
--- a/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.h
+++ b/samples/server/petstore/cpp-pistache/impl/StoreApiImpl.h
@@ -48,7 +48,7 @@ class StoreApiImpl : public org::openapitools::server::api::StoreApi {
     void delete_order(const std::string &orderId, Pistache::Http::ResponseWriter &response);
     void get_inventory(Pistache::Http::ResponseWriter &response);
     void get_order_by_id(const int64_t &orderId, Pistache::Http::ResponseWriter &response);
-    void place_order(const Order &order, Pistache::Http::ResponseWriter &response);
+    void place_order(const Order &body, Pistache::Http::ResponseWriter &response);
 
 };
 
diff --git a/samples/server/petstore/cpp-pistache/impl/UserApiImpl.cpp b/samples/server/petstore/cpp-pistache/impl/UserApiImpl.cpp
index a810c266fdf0..2e7b06d956d8 100644
--- a/samples/server/petstore/cpp-pistache/impl/UserApiImpl.cpp
+++ b/samples/server/petstore/cpp-pistache/impl/UserApiImpl.cpp
@@ -23,13 +23,13 @@ UserApiImpl::UserApiImpl(std::shared_ptr<Pistache::Rest::Router> rtr)
     : UserApi(rtr)
     { }
 
-void UserApiImpl::create_user(const User &user, Pistache::Http::ResponseWriter &response) {
+void UserApiImpl::create_user(const User &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
-void UserApiImpl::create_users_with_array_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response) {
+void UserApiImpl::create_users_with_array_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
-void UserApiImpl::create_users_with_list_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response) {
+void UserApiImpl::create_users_with_list_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
 void UserApiImpl::delete_user(const std::string &username, Pistache::Http::ResponseWriter &response) {
@@ -44,7 +44,7 @@ void UserApiImpl::login_user(const Pistache::Optional<std::string> &username, co
 void UserApiImpl::logout_user(Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
-void UserApiImpl::update_user(const std::string &username, const User &user, Pistache::Http::ResponseWriter &response) {
+void UserApiImpl::update_user(const std::string &username, const User &body, Pistache::Http::ResponseWriter &response) {
     response.send(Pistache::Http::Code::Ok, "Do some magic\n");
 }
 
diff --git a/samples/server/petstore/cpp-pistache/impl/UserApiImpl.h b/samples/server/petstore/cpp-pistache/impl/UserApiImpl.h
index 771f3eaeef24..9bde4fc572a2 100644
--- a/samples/server/petstore/cpp-pistache/impl/UserApiImpl.h
+++ b/samples/server/petstore/cpp-pistache/impl/UserApiImpl.h
@@ -45,14 +45,14 @@ class UserApiImpl : public org::openapitools::server::api::UserApi {
     UserApiImpl(std::shared_ptr<Pistache::Rest::Router>);
     ~UserApiImpl() {}
 
-    void create_user(const User &user, Pistache::Http::ResponseWriter &response);
-    void create_users_with_array_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response);
-    void create_users_with_list_input(const std::vector<User> &user, Pistache::Http::ResponseWriter &response);
+    void create_user(const User &body, Pistache::Http::ResponseWriter &response);
+    void create_users_with_array_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response);
+    void create_users_with_list_input(const std::vector<User> &body, Pistache::Http::ResponseWriter &response);
     void delete_user(const std::string &username, Pistache::Http::ResponseWriter &response);
     void get_user_by_name(const std::string &username, Pistache::Http::ResponseWriter &response);
     void login_user(const Pistache::Optional<std::string> &username, const Pistache::Optional<std::string> &password, Pistache::Http::ResponseWriter &response);
     void logout_user(Pistache::Http::ResponseWriter &response);
-    void update_user(const std::string &username, const User &user, Pistache::Http::ResponseWriter &response);
+    void update_user(const std::string &username, const User &body, Pistache::Http::ResponseWriter &response);
 
 };
 
diff --git a/samples/server/petstore/cpp-pistache/model/ApiResponse.cpp b/samples/server/petstore/cpp-pistache/model/ApiResponse.cpp
index d316194ce8cb..abcbbf3db084 100644
--- a/samples/server/petstore/cpp-pistache/model/ApiResponse.cpp
+++ b/samples/server/petstore/cpp-pistache/model/ApiResponse.cpp
@@ -38,45 +38,36 @@ void ApiResponse::validate()
     // TODO: implement validation
 }
 
-nlohmann::json ApiResponse::toJson() const
+void to_json(nlohmann::json& j, const ApiResponse& o)
 {
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_CodeIsSet)
-    {
-        val["code"] = m_Code;
-    }
-    if(m_TypeIsSet)
-    {
-        val["type"] = ModelBase::toJson(m_Type);
-    }
-    if(m_MessageIsSet)
-    {
-        val["message"] = ModelBase::toJson(m_Message);
-    }
-    
-
-    return val;
+    j = nlohmann::json();
+    if(o.codeIsSet())
+        j["code"] = o.m_Code;
+    if(o.typeIsSet())
+        j["type"] = o.m_Type;
+    if(o.messageIsSet())
+        j["message"] = o.m_Message;
 }
 
-void ApiResponse::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, ApiResponse& o)
 {
-    if(val.find("code") != val.end())
+    if(!j.at("code").is_null())
     {
-        setCode(val.at("code"));
-    }
-    if(val.find("type") != val.end())
+        j.at("code").get_to(o.m_Code);
+        o.m_CodeIsSet = true;
+    } 
+    if(!j.at("type").is_null())
     {
-        setType(val.at("type"));
-    }
-    if(val.find("message") != val.end())
+        j.at("type").get_to(o.m_Type);
+        o.m_TypeIsSet = true;
+    } 
+    if(!j.at("message").is_null())
     {
-        setMessage(val.at("message"));
-    }
-    
+        j.at("message").get_to(o.m_Message);
+        o.m_MessageIsSet = true;
+    } 
 }
 
-
 int32_t ApiResponse::getCode() const
 {
     return m_Code;
diff --git a/samples/server/petstore/cpp-pistache/model/ApiResponse.h b/samples/server/petstore/cpp-pistache/model/ApiResponse.h
index fb8cc43693fa..3291251d8cb5 100644
--- a/samples/server/petstore/cpp-pistache/model/ApiResponse.h
+++ b/samples/server/petstore/cpp-pistache/model/ApiResponse.h
@@ -19,9 +19,8 @@
 #define ApiResponse_H_
 
 
-#include "ModelBase.h"
-
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -32,19 +31,12 @@ namespace model {
 /// Describes the result of uploading an image resource
 /// </summary>
 class  ApiResponse
-    : public ModelBase
 {
 public:
     ApiResponse();
     virtual ~ApiResponse();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// ApiResponse members
@@ -71,6 +63,8 @@ class  ApiResponse
     bool messageIsSet() const;
     void unsetMessage();
 
+    friend void to_json(nlohmann::json& j, const ApiResponse& o);
+    friend void from_json(const nlohmann::json& j, ApiResponse& o);
 protected:
     int32_t m_Code;
     bool m_CodeIsSet;
diff --git a/samples/server/petstore/cpp-pistache/model/Category.cpp b/samples/server/petstore/cpp-pistache/model/Category.cpp
index 9ae18edc686d..856540a37542 100644
--- a/samples/server/petstore/cpp-pistache/model/Category.cpp
+++ b/samples/server/petstore/cpp-pistache/model/Category.cpp
@@ -36,37 +36,29 @@ void Category::validate()
     // TODO: implement validation
 }
 
-nlohmann::json Category::toJson() const
+void to_json(nlohmann::json& j, const Category& o)
 {
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_IdIsSet)
-    {
-        val["id"] = m_Id;
-    }
-    if(m_NameIsSet)
-    {
-        val["name"] = ModelBase::toJson(m_Name);
-    }
-    
-
-    return val;
+    j = nlohmann::json();
+    if(o.idIsSet())
+        j["id"] = o.m_Id;
+    if(o.nameIsSet())
+        j["name"] = o.m_Name;
 }
 
-void Category::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, Category& o)
 {
-    if(val.find("id") != val.end())
+    if(!j.at("id").is_null())
     {
-        setId(val.at("id"));
-    }
-    if(val.find("name") != val.end())
+        j.at("id").get_to(o.m_Id);
+        o.m_IdIsSet = true;
+    } 
+    if(!j.at("name").is_null())
     {
-        setName(val.at("name"));
-    }
-    
+        j.at("name").get_to(o.m_Name);
+        o.m_NameIsSet = true;
+    } 
 }
 
-
 int64_t Category::getId() const
 {
     return m_Id;
diff --git a/samples/server/petstore/cpp-pistache/model/Category.h b/samples/server/petstore/cpp-pistache/model/Category.h
index 4ed3fafc8c8c..4018607b4350 100644
--- a/samples/server/petstore/cpp-pistache/model/Category.h
+++ b/samples/server/petstore/cpp-pistache/model/Category.h
@@ -19,9 +19,8 @@
 #define Category_H_
 
 
-#include "ModelBase.h"
-
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -32,19 +31,12 @@ namespace model {
 /// A category for a pet
 /// </summary>
 class  Category
-    : public ModelBase
 {
 public:
     Category();
     virtual ~Category();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// Category members
@@ -64,6 +56,8 @@ class  Category
     bool nameIsSet() const;
     void unsetName();
 
+    friend void to_json(nlohmann::json& j, const Category& o);
+    friend void from_json(const nlohmann::json& j, Category& o);
 protected:
     int64_t m_Id;
     bool m_IdIsSet;
diff --git a/samples/server/petstore/cpp-pistache/model/ModelBase.cpp b/samples/server/petstore/cpp-pistache/model/ModelBase.cpp
deleted file mode 100644
index 19910b9d6012..000000000000
--- a/samples/server/petstore/cpp-pistache/model/ModelBase.cpp
+++ /dev/null
@@ -1,66 +0,0 @@
-/**
-* OpenAPI Petstore
-* This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
-*
-* OpenAPI spec version: 1.0.0
-* 
-*
-* NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
-* https://openapi-generator.tech
-* Do not edit the class manually.
-*/
-#include "ModelBase.h"
-
-namespace org {
-namespace openapitools {
-namespace server {
-namespace model {
-
-ModelBase::ModelBase()
-{
-}
-ModelBase::~ModelBase()
-{
-}
-
-std::string ModelBase::toJson( std::string const& value )
-{
-    return value;
-}
-
-std::string ModelBase::toJson( std::time_t const& value )
-{
-    char buf[sizeof "2011-10-08T07:07:09Z"];
-    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&value));
-    return buf;
-}
-
-int32_t ModelBase::toJson( int32_t const value )
-{
-    return value;
-}
-
-int64_t ModelBase::toJson( int64_t const value )
-{
-    return value;
-}
-
-double ModelBase::toJson( double const value )
-{
-    return value;
-}
-
-bool ModelBase::toJson( bool const value )
-{
-    return value;
-}
-
-nlohmann::json ModelBase::toJson(ModelBase const& content )
-{
-    return content.toJson();
-}
-
-}
-}
-}
-}
diff --git a/samples/server/petstore/cpp-pistache/model/ModelBase.h b/samples/server/petstore/cpp-pistache/model/ModelBase.h
deleted file mode 100644
index 6bc0dc921243..000000000000
--- a/samples/server/petstore/cpp-pistache/model/ModelBase.h
+++ /dev/null
@@ -1,139 +0,0 @@
-/**
-* OpenAPI Petstore
-* This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
-*
-* OpenAPI spec version: 1.0.0
-* 
-*
-* NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
-* https://openapi-generator.tech
-* Do not edit the class manually.
-*/
-/*
- * ModelBase.h
- *
- * This is the base class for all model classes
- */
-
-#ifndef ModelBase_H_
-#define ModelBase_H_
-
-
-#include "json.hpp"
-#include <ctime>
-#include <string>
-#include <vector>
-#include <map>
-
-namespace org {
-namespace openapitools {
-namespace server {
-namespace model {
-
-class  ModelBase
-{
-public:
-    ModelBase();
-    virtual ~ModelBase();
-
-    virtual void validate() = 0;
-
-    virtual nlohmann::json toJson() const = 0;
-    virtual void fromJson(const nlohmann::json& json) = 0;
-
-    static std::string toJson(  std::string const& value );
-    static std::string toJson(  std::time_t const& value );
-    static int32_t toJson( int32_t const value );
-    static int64_t toJson( int64_t const value );
-    static double toJson( double const value );
-    static bool toJson( bool const value );
-    static nlohmann::json toJson(ModelBase const& content ); 
-};
-
-class ArrayHelper {
-private:
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static void itemFromJson(T& item, const nlohmann::json& json){
-        item = json;
-    }
-    static void itemFromJson(ModelBase& item, const nlohmann::json& json){
-        item.fromJson(json);
-    }
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static nlohmann::json itemtoJson(const T& item){
-        return item;
-    }
-    static nlohmann::json itemtoJson(const ModelBase& item){
-        return item.toJson();
-    }
-public:
-    template<typename T>
-    static std::vector<T> fromJson(const nlohmann::json& json) {
-        std::vector<T> val;
-        if (!json.empty()) {
-            for (const auto& item : json.items()) {
-                T entry;
-                itemFromJson(entry, item.value());
-                val.push_back(entry);
-            }
-        }
-        return val;
-    }
-    template<typename T>
-    static nlohmann::json toJson(const std::vector<T>& val) {
-        nlohmann::json json;
-        for(const auto& item : val){
-            json.push_back(itemtoJson(item));
-        }
-        return json;
-    }
-};
-
-class MapHelper {
-private:
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static void itemFromJson(T &item, const nlohmann::json& json){
-        item = json;
-    }
-    static void itemFromJson(ModelBase &item, const nlohmann::json& json){
-        item.fromJson(json);
-    }
-    template<typename T, typename std::enable_if<!std::is_base_of<ModelBase, T>::value>::value>
-    static nlohmann::json itemtoJson(const T& item){
-        return item;
-    }
-    static nlohmann::json itemtoJson(const ModelBase& item){
-        return item.toJson();
-    }
-
-public:
-    template<typename T>
-    static std::map<std::string, T> fromJson(const nlohmann::json& json) {
-        std::map<std::string, T> val;
-        if (!json.empty()) {
-            for (const auto& item : json.items()) {
-                T entry;
-                itemfromJson(entry, item.value());
-                val.insert(val.end(),
-                        std::pair<std::string, T>(item.key(), entry));
-            }
-        }
-        return val;
-    }
-    template<typename T>
-    static nlohmann::json toJson(const std::map<std::string, T>& val) {
-        nlohmann::json json;
-        for (const auto& item : val) {
-          nlohmann::json jitem = itemtoJson(item.second);
-          json[item.first] = jitem;
-        }
-        return json;
-    }
-};
-
-}
-}
-}
-}
-
-#endif /* ModelBase_H_ */
diff --git a/samples/server/petstore/cpp-pistache/model/Order.cpp b/samples/server/petstore/cpp-pistache/model/Order.cpp
index 6baadd493acc..0d6c43da14f5 100644
--- a/samples/server/petstore/cpp-pistache/model/Order.cpp
+++ b/samples/server/petstore/cpp-pistache/model/Order.cpp
@@ -44,70 +44,57 @@ void Order::validate()
     // TODO: implement validation
 }
 
-nlohmann::json Order::toJson() const
-{
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_IdIsSet)
-    {
-        val["id"] = m_Id;
-    }
-    if(m_PetIdIsSet)
-    {
-        val["petId"] = m_PetId;
-    }
-    if(m_QuantityIsSet)
-    {
-        val["quantity"] = m_Quantity;
-    }
-    if(m_ShipDateIsSet)
-    {
-        val["shipDate"] = ModelBase::toJson(m_ShipDate);
-    }
-    if(m_StatusIsSet)
-    {
-        val["status"] = ModelBase::toJson(m_Status);
-    }
-    if(m_CompleteIsSet)
-    {
-        val["complete"] = m_Complete;
-    }
-    
-
-    return val;
+void to_json(nlohmann::json& j, const Order& o)
+{
+    j = nlohmann::json();
+    if(o.idIsSet())
+        j["id"] = o.m_Id;
+    if(o.petIdIsSet())
+        j["petId"] = o.m_PetId;
+    if(o.quantityIsSet())
+        j["quantity"] = o.m_Quantity;
+    if(o.shipDateIsSet())
+        j["shipDate"] = o.m_ShipDate;
+    if(o.statusIsSet())
+        j["status"] = o.m_Status;
+    if(o.completeIsSet())
+        j["complete"] = o.m_Complete;
 }
 
-void Order::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, Order& o)
 {
-    if(val.find("id") != val.end())
+    if(!j.at("id").is_null())
     {
-        setId(val.at("id"));
-    }
-    if(val.find("petId") != val.end())
+        j.at("id").get_to(o.m_Id);
+        o.m_IdIsSet = true;
+    } 
+    if(!j.at("petId").is_null())
     {
-        setPetId(val.at("petId"));
-    }
-    if(val.find("quantity") != val.end())
+        j.at("petId").get_to(o.m_PetId);
+        o.m_PetIdIsSet = true;
+    } 
+    if(!j.at("quantity").is_null())
     {
-        setQuantity(val.at("quantity"));
-    }
-    if(val.find("shipDate") != val.end())
+        j.at("quantity").get_to(o.m_Quantity);
+        o.m_QuantityIsSet = true;
+    } 
+    if(!j.at("shipDate").is_null())
     {
-        setShipDate(val.at("shipDate"));
-        
-    }
-    if(val.find("status") != val.end())
+        j.at("shipDate").get_to(o.m_ShipDate);
+        o.m_ShipDateIsSet = true;
+    } 
+    if(!j.at("status").is_null())
     {
-        setStatus(val.at("status"));
-    }
-    if(val.find("complete") != val.end())
+        j.at("status").get_to(o.m_Status);
+        o.m_StatusIsSet = true;
+    } 
+    if(!j.at("complete").is_null())
     {
-        setComplete(val.at("complete"));
-    }
-    
+        j.at("complete").get_to(o.m_Complete);
+        o.m_CompleteIsSet = true;
+    } 
 }
 
-
 int64_t Order::getId() const
 {
     return m_Id;
diff --git a/samples/server/petstore/cpp-pistache/model/Order.h b/samples/server/petstore/cpp-pistache/model/Order.h
index bc77d0910597..b4d4598b749a 100644
--- a/samples/server/petstore/cpp-pistache/model/Order.h
+++ b/samples/server/petstore/cpp-pistache/model/Order.h
@@ -19,9 +19,8 @@
 #define Order_H_
 
 
-#include "ModelBase.h"
-
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -32,19 +31,12 @@ namespace model {
 /// An order for a pets from the pet store
 /// </summary>
 class  Order
-    : public ModelBase
 {
 public:
     Order();
     virtual ~Order();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// Order members
@@ -92,6 +84,8 @@ class  Order
     bool completeIsSet() const;
     void unsetComplete();
 
+    friend void to_json(nlohmann::json& j, const Order& o);
+    friend void from_json(const nlohmann::json& j, Order& o);
 protected:
     int64_t m_Id;
     bool m_IdIsSet;
diff --git a/samples/server/petstore/cpp-pistache/model/Pet.cpp b/samples/server/petstore/cpp-pistache/model/Pet.cpp
index 834ac8ff6326..cecbac69840d 100644
--- a/samples/server/petstore/cpp-pistache/model/Pet.cpp
+++ b/samples/server/petstore/cpp-pistache/model/Pet.cpp
@@ -39,103 +39,47 @@ void Pet::validate()
     // TODO: implement validation
 }
 
-nlohmann::json Pet::toJson() const
-{
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_IdIsSet)
-    {
-        val["id"] = m_Id;
-    }
-    if(m_CategoryIsSet)
-    {
-        val["category"] = ModelBase::toJson(m_Category);
-    }
-    val["name"] = ModelBase::toJson(m_Name);
-    {
-        nlohmann::json jsonArray;
-        for( auto& item : m_PhotoUrls )
-        {
-            jsonArray.push_back(ModelBase::toJson(item));
-        }
-        val["photoUrls"] = jsonArray;
-        
-    }
-    {
-        nlohmann::json jsonArray;
-        for( auto& item : m_Tags )
-        {
-            jsonArray.push_back(ModelBase::toJson(item));
-        }
-        
-        if(jsonArray.size() > 0)
-        {
-            val["tags"] = jsonArray;
-        } 
-    }
-    if(m_StatusIsSet)
-    {
-        val["status"] = ModelBase::toJson(m_Status);
-    }
-    
-
-    return val;
+void to_json(nlohmann::json& j, const Pet& o)
+{
+    j = nlohmann::json();
+    if(o.idIsSet())
+        j["id"] = o.m_Id;
+    if(o.categoryIsSet())
+        j["category"] = o.m_Category;
+    j["name"] = o.m_Name;
+    j["photoUrls"] = o.m_PhotoUrls;
+    if(o.tagsIsSet())
+        j["tags"] = o.m_Tags;
+    if(o.statusIsSet())
+        j["status"] = o.m_Status;
 }
 
-void Pet::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, Pet& o)
 {
-    if(val.find("id") != val.end())
+    if(!j.at("id").is_null())
     {
-        setId(val.at("id"));
-    }
-    if(val.find("category") != val.end())
+        j.at("id").get_to(o.m_Id);
+        o.m_IdIsSet = true;
+    } 
+    if(!j.at("category").is_null())
     {
-        if(!val["category"].is_null())
-        {
-            Category newItem;
-            newItem.fromJson(val["category"]);
-            setCategory( newItem );
-        }
-        
-    }
-    setName(val.at("name"));
+        j.at("category").get_to(o.m_Category);
+        o.m_CategoryIsSet = true;
+    } 
+    j.at("name").get_to(o.m_Name);
+    j.at("photoUrls").get_to(o.m_PhotoUrls);
+    if(!j.at("tags").is_null())
     {
-        m_PhotoUrls.clear();
-                    for( auto& item : val["photoUrls"] )
-            {
-                m_PhotoUrls.push_back(item);
-                
-            }
-    }
+        j.at("tags").get_to(o.m_Tags);
+        o.m_TagsIsSet = true;
+    } 
+    if(!j.at("status").is_null())
     {
-        m_Tags.clear();
-        if(val.find("tags") != val.end())
-        {
-            for( auto& item : val["tags"] )
-            {
-                
-                if(item.is_null())
-                {
-                    m_Tags.push_back( Tag() );
-                }
-                else
-                {
-                    Tag newItem;
-                    newItem.fromJson(item);
-                    m_Tags.push_back( newItem );
-                }
-                
-            }
-        }
-    }
-    if(val.find("status") != val.end())
-    {
-        setStatus(val.at("status"));
-    }
-    
+        j.at("status").get_to(o.m_Status);
+        o.m_StatusIsSet = true;
+    } 
 }
 
-
 int64_t Pet::getId() const
 {
     return m_Id;
diff --git a/samples/server/petstore/cpp-pistache/model/Pet.h b/samples/server/petstore/cpp-pistache/model/Pet.h
index 6f7e9a565a63..22eeb9570f48 100644
--- a/samples/server/petstore/cpp-pistache/model/Pet.h
+++ b/samples/server/petstore/cpp-pistache/model/Pet.h
@@ -19,12 +19,11 @@
 #define Pet_H_
 
 
-#include "ModelBase.h"
-
 #include "Tag.h"
 #include <string>
 #include "Category.h"
 #include <vector>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -35,19 +34,12 @@ namespace model {
 /// A pet for sale in the pet store
 /// </summary>
 class  Pet
-    : public ModelBase
 {
 public:
     Pet();
     virtual ~Pet();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// Pet members
@@ -89,6 +81,8 @@ class  Pet
     bool statusIsSet() const;
     void unsetStatus();
 
+    friend void to_json(nlohmann::json& j, const Pet& o);
+    friend void from_json(const nlohmann::json& j, Pet& o);
 protected:
     int64_t m_Id;
     bool m_IdIsSet;
diff --git a/samples/server/petstore/cpp-pistache/model/Tag.cpp b/samples/server/petstore/cpp-pistache/model/Tag.cpp
index 9efe5aeb9dbe..19a4e27ed2ed 100644
--- a/samples/server/petstore/cpp-pistache/model/Tag.cpp
+++ b/samples/server/petstore/cpp-pistache/model/Tag.cpp
@@ -36,37 +36,29 @@ void Tag::validate()
     // TODO: implement validation
 }
 
-nlohmann::json Tag::toJson() const
+void to_json(nlohmann::json& j, const Tag& o)
 {
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_IdIsSet)
-    {
-        val["id"] = m_Id;
-    }
-    if(m_NameIsSet)
-    {
-        val["name"] = ModelBase::toJson(m_Name);
-    }
-    
-
-    return val;
+    j = nlohmann::json();
+    if(o.idIsSet())
+        j["id"] = o.m_Id;
+    if(o.nameIsSet())
+        j["name"] = o.m_Name;
 }
 
-void Tag::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, Tag& o)
 {
-    if(val.find("id") != val.end())
+    if(!j.at("id").is_null())
     {
-        setId(val.at("id"));
-    }
-    if(val.find("name") != val.end())
+        j.at("id").get_to(o.m_Id);
+        o.m_IdIsSet = true;
+    } 
+    if(!j.at("name").is_null())
     {
-        setName(val.at("name"));
-    }
-    
+        j.at("name").get_to(o.m_Name);
+        o.m_NameIsSet = true;
+    } 
 }
 
-
 int64_t Tag::getId() const
 {
     return m_Id;
diff --git a/samples/server/petstore/cpp-pistache/model/Tag.h b/samples/server/petstore/cpp-pistache/model/Tag.h
index f46aecf78b40..bb5dff9f922b 100644
--- a/samples/server/petstore/cpp-pistache/model/Tag.h
+++ b/samples/server/petstore/cpp-pistache/model/Tag.h
@@ -19,9 +19,8 @@
 #define Tag_H_
 
 
-#include "ModelBase.h"
-
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -32,19 +31,12 @@ namespace model {
 /// A tag for a pet
 /// </summary>
 class  Tag
-    : public ModelBase
 {
 public:
     Tag();
     virtual ~Tag();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// Tag members
@@ -64,6 +56,8 @@ class  Tag
     bool nameIsSet() const;
     void unsetName();
 
+    friend void to_json(nlohmann::json& j, const Tag& o);
+    friend void from_json(const nlohmann::json& j, Tag& o);
 protected:
     int64_t m_Id;
     bool m_IdIsSet;
diff --git a/samples/server/petstore/cpp-pistache/model/User.cpp b/samples/server/petstore/cpp-pistache/model/User.cpp
index 186fc58924d2..6bc726b0563d 100644
--- a/samples/server/petstore/cpp-pistache/model/User.cpp
+++ b/samples/server/petstore/cpp-pistache/model/User.cpp
@@ -48,85 +48,71 @@ void User::validate()
     // TODO: implement validation
 }
 
-nlohmann::json User::toJson() const
-{
-    nlohmann::json val = nlohmann::json::object();
-
-    if(m_IdIsSet)
-    {
-        val["id"] = m_Id;
-    }
-    if(m_UsernameIsSet)
-    {
-        val["username"] = ModelBase::toJson(m_Username);
-    }
-    if(m_FirstNameIsSet)
-    {
-        val["firstName"] = ModelBase::toJson(m_FirstName);
-    }
-    if(m_LastNameIsSet)
-    {
-        val["lastName"] = ModelBase::toJson(m_LastName);
-    }
-    if(m_EmailIsSet)
-    {
-        val["email"] = ModelBase::toJson(m_Email);
-    }
-    if(m_PasswordIsSet)
-    {
-        val["password"] = ModelBase::toJson(m_Password);
-    }
-    if(m_PhoneIsSet)
-    {
-        val["phone"] = ModelBase::toJson(m_Phone);
-    }
-    if(m_UserStatusIsSet)
-    {
-        val["userStatus"] = m_UserStatus;
-    }
-    
-
-    return val;
+void to_json(nlohmann::json& j, const User& o)
+{
+    j = nlohmann::json();
+    if(o.idIsSet())
+        j["id"] = o.m_Id;
+    if(o.usernameIsSet())
+        j["username"] = o.m_Username;
+    if(o.firstNameIsSet())
+        j["firstName"] = o.m_FirstName;
+    if(o.lastNameIsSet())
+        j["lastName"] = o.m_LastName;
+    if(o.emailIsSet())
+        j["email"] = o.m_Email;
+    if(o.passwordIsSet())
+        j["password"] = o.m_Password;
+    if(o.phoneIsSet())
+        j["phone"] = o.m_Phone;
+    if(o.userStatusIsSet())
+        j["userStatus"] = o.m_UserStatus;
 }
 
-void User::fromJson(const nlohmann::json& val)
+void from_json(const nlohmann::json& j, User& o)
 {
-    if(val.find("id") != val.end())
+    if(!j.at("id").is_null())
     {
-        setId(val.at("id"));
-    }
-    if(val.find("username") != val.end())
+        j.at("id").get_to(o.m_Id);
+        o.m_IdIsSet = true;
+    } 
+    if(!j.at("username").is_null())
     {
-        setUsername(val.at("username"));
-    }
-    if(val.find("firstName") != val.end())
+        j.at("username").get_to(o.m_Username);
+        o.m_UsernameIsSet = true;
+    } 
+    if(!j.at("firstName").is_null())
     {
-        setFirstName(val.at("firstName"));
-    }
-    if(val.find("lastName") != val.end())
+        j.at("firstName").get_to(o.m_FirstName);
+        o.m_FirstNameIsSet = true;
+    } 
+    if(!j.at("lastName").is_null())
     {
-        setLastName(val.at("lastName"));
-    }
-    if(val.find("email") != val.end())
+        j.at("lastName").get_to(o.m_LastName);
+        o.m_LastNameIsSet = true;
+    } 
+    if(!j.at("email").is_null())
     {
-        setEmail(val.at("email"));
-    }
-    if(val.find("password") != val.end())
+        j.at("email").get_to(o.m_Email);
+        o.m_EmailIsSet = true;
+    } 
+    if(!j.at("password").is_null())
     {
-        setPassword(val.at("password"));
-    }
-    if(val.find("phone") != val.end())
+        j.at("password").get_to(o.m_Password);
+        o.m_PasswordIsSet = true;
+    } 
+    if(!j.at("phone").is_null())
     {
-        setPhone(val.at("phone"));
-    }
-    if(val.find("userStatus") != val.end())
+        j.at("phone").get_to(o.m_Phone);
+        o.m_PhoneIsSet = true;
+    } 
+    if(!j.at("userStatus").is_null())
     {
-        setUserStatus(val.at("userStatus"));
-    }
-    
+        j.at("userStatus").get_to(o.m_UserStatus);
+        o.m_UserStatusIsSet = true;
+    } 
 }
 
-
 int64_t User::getId() const
 {
     return m_Id;
diff --git a/samples/server/petstore/cpp-pistache/model/User.h b/samples/server/petstore/cpp-pistache/model/User.h
index a52a183cd46d..4b8cd2b19626 100644
--- a/samples/server/petstore/cpp-pistache/model/User.h
+++ b/samples/server/petstore/cpp-pistache/model/User.h
@@ -19,9 +19,8 @@
 #define User_H_
 
 
-#include "ModelBase.h"
-
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace org {
 namespace openapitools {
@@ -32,19 +31,12 @@ namespace model {
 /// A User who is purchasing from the pet store
 /// </summary>
 class  User
-    : public ModelBase
 {
 public:
     User();
     virtual ~User();
 
-    /////////////////////////////////////////////
-    /// ModelBase overrides
-
-    void validate() override;
-
-    nlohmann::json toJson() const override;
-    void fromJson(const nlohmann::json& json) override;
+    void validate();
 
     /////////////////////////////////////////////
     /// User members
@@ -106,6 +98,8 @@ class  User
     bool userStatusIsSet() const;
     void unsetUserStatus();
 
+    friend void to_json(nlohmann::json& j, const User& o);
+    friend void from_json(const nlohmann::json& j, User& o);
 protected:
     int64_t m_Id;
     bool m_IdIsSet;