diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
index 20120634dcd2..e7c2aaef7530 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
@@ -106,6 +106,7 @@ public class InlineModelResolver {
 
                     // create request body
                     RequestBody rb = new RequestBody();
+                    rb.setRequired(requestBody.getRequired());
                     Content content = new Content();
                     MediaType mt = new MediaType();
                     Schema schema = new Schema();
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/InlineModelResolverTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/InlineModelResolverTest.java
index 2735f15cb9de..de8015de9f6e 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/InlineModelResolverTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/InlineModelResolverTest.java
@@ -328,6 +328,9 @@ public class InlineModelResolverTest {
 
         RequestBody requestBodyReference = openAPI.getPaths().get("/resolve_inline_request_body_with_required").getPost().getRequestBody();
         assertTrue(requestBodyReference.getRequired());
+
+        RequestBody referencedRequestBody = ModelUtils.getReferencedRequestBody(openAPI, requestBodyReference);
+        assertTrue(referencedRequestBody.getRequired());
     }
 
     @Test
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/AnotherFakeApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/AnotherFakeApiTest.java
index 9dbe5a227817..b5e26401d2f3 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/AnotherFakeApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/AnotherFakeApiTest.java
@@ -26,12 +26,12 @@ public class AnotherFakeApiTest {
     /**
      * To test special tags
      *
-     * To test special tags
+     * To test special tags and operation ID starting with number
      */
     @Test
-    public void testSpecialTagsTest() {
-        Client client = null;
-        // Client response = api.testSpecialTags(client);
+    public void call123testSpecialTagsTest() {
+        Client body = null;
+        // Client response = api.call123testSpecialTags(body);
 
         // TODO: test validations
     }
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeApiTest.java
index bbb4a9bbc854..f454452f462e 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeApiTest.java
@@ -51,8 +51,8 @@ public class FakeApiTest {
      */
     @Test
     public void fakeOuterCompositeSerializeTest() {
-        OuterComposite outerComposite = null;
-        // OuterComposite response = api.fakeOuterCompositeSerialize(outerComposite);
+        OuterComposite body = null;
+        // OuterComposite response = api.fakeOuterCompositeSerialize(body);
 
         // TODO: test validations
     }
@@ -93,8 +93,8 @@ public class FakeApiTest {
      */
     @Test
     public void testBodyWithFileSchemaTest() {
-        FileSchemaTestClass fileSchemaTestClass = null;
-        // api.testBodyWithFileSchema(fileSchemaTestClass);
+        FileSchemaTestClass body = null;
+        // api.testBodyWithFileSchema(body);
 
         // TODO: test validations
     }
@@ -108,8 +108,8 @@ public class FakeApiTest {
     @Test
     public void testBodyWithQueryParamsTest() {
         String query = null;
-        User user = null;
-        // api.testBodyWithQueryParams(query, user);
+        User body = null;
+        // api.testBodyWithQueryParams(query, body);
 
         // TODO: test validations
     }
@@ -124,10 +124,10 @@ public class FakeApiTest {
      */
     @Test
     public void testBodyWithQueryParamsTestQueryMap() {
-        User user = null;
+        User body = null;
         FakeApi.TestBodyWithQueryParamsQueryParams queryParams = new FakeApi.TestBodyWithQueryParamsQueryParams()
             .query(null);
-        // api.testBodyWithQueryParams(user, queryParams);
+        // api.testBodyWithQueryParams(body, queryParams);
 
     // TODO: test validations
     }
@@ -139,8 +139,8 @@ public class FakeApiTest {
      */
     @Test
     public void testClientModelTest() {
-        Client client = null;
-        // Client response = api.testClientModel(client);
+        Client body = null;
+        // Client response = api.testClientModel(body);
 
         // TODO: test validations
     }
@@ -264,8 +264,8 @@ public class FakeApiTest {
      */
     @Test
     public void testInlineAdditionalPropertiesTest() {
-        Map<String, String> requestBody = null;
-        // api.testInlineAdditionalProperties(requestBody);
+        Map<String, String> param = null;
+        // api.testInlineAdditionalProperties(param);
 
         // TODO: test validations
     }
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeClassnameTags123ApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeClassnameTags123ApiTest.java
index 192ca5e1e30d..badb867ce81f 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeClassnameTags123ApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/FakeClassnameTags123ApiTest.java
@@ -30,8 +30,8 @@ public class FakeClassnameTags123ApiTest {
      */
     @Test
     public void testClassnameTest() {
-        Client client = null;
-        // Client response = api.testClassname(client);
+        Client body = null;
+        // Client response = api.testClassname(body);
 
         // TODO: test validations
     }
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/PetApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/PetApiTest.java
index a22f839b0db7..b42adee44e75 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/PetApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/PetApiTest.java
@@ -32,8 +32,8 @@ public class PetApiTest {
      */
     @Test
     public void addPetTest() {
-        Pet pet = null;
-        // api.addPet(pet);
+        Pet body = null;
+        // api.addPet(body);
 
         // TODO: test validations
     }
@@ -135,8 +135,8 @@ public class PetApiTest {
      */
     @Test
     public void updatePetTest() {
-        Pet pet = null;
-        // api.updatePet(pet);
+        Pet body = null;
+        // api.updatePet(body);
 
         // TODO: test validations
     }
@@ -174,4 +174,20 @@ public class PetApiTest {
     }
 
     
+    /**
+     * uploads an image (required)
+     *
+     * 
+     */
+    @Test
+    public void uploadFileWithRequiredFileTest() {
+        Long petId = null;
+        File requiredFile = null;
+        String additionalMetadata = null;
+        // ModelApiResponse response = api.uploadFileWithRequiredFile(petId, requiredFile, additionalMetadata);
+
+        // TODO: test validations
+    }
+
+    
 }
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/StoreApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/StoreApiTest.java
index bdb0b7a1e096..07a48ec6e63c 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/StoreApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/StoreApiTest.java
@@ -71,8 +71,8 @@ public class StoreApiTest {
      */
     @Test
     public void placeOrderTest() {
-        Order order = null;
-        // Order response = api.placeOrder(order);
+        Order body = null;
+        // Order response = api.placeOrder(body);
 
         // TODO: test validations
     }
diff --git a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/UserApiTest.java b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/UserApiTest.java
index c1d841f1e8a4..2656fb4cc920 100644
--- a/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/UserApiTest.java
+++ b/samples/client/petstore/java/feign/src/test/java/org/openapitools/client/api/UserApiTest.java
@@ -30,8 +30,8 @@ public class UserApiTest {
      */
     @Test
     public void createUserTest() {
-        User user = null;
-        // api.createUser(user);
+        User body = null;
+        // api.createUser(body);
 
         // TODO: test validations
     }
@@ -44,8 +44,8 @@ public class UserApiTest {
      */
     @Test
     public void createUsersWithArrayInputTest() {
-        List<User> user = null;
-        // api.createUsersWithArrayInput(user);
+        List<User> body = null;
+        // api.createUsersWithArrayInput(body);
 
         // TODO: test validations
     }
@@ -58,8 +58,8 @@ public class UserApiTest {
      */
     @Test
     public void createUsersWithListInputTest() {
-        List<User> user = null;
-        // api.createUsersWithListInput(user);
+        List<User> body = null;
+        // api.createUsersWithListInput(body);
 
         // TODO: test validations
     }
@@ -146,8 +146,8 @@ public class UserApiTest {
     @Test
     public void updateUserTest() {
         String username = null;
-        User user = null;
-        // api.updateUser(username, user);
+        User body = null;
+        // api.updateUser(username, body);
 
         // TODO: test validations
     }
diff --git a/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.jar b/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 000000000000..1948b9074f10
Binary files /dev/null and b/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.properties b/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 000000000000..687a59667027
--- /dev/null
+++ b/samples/openapi3/client/petstore/kotlin/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-all.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/samples/openapi3/client/petstore/kotlin/gradlew b/samples/openapi3/client/petstore/kotlin/gradlew
new file mode 100755
index 000000000000..cccdd3d517fc
--- /dev/null
+++ b/samples/openapi3/client/petstore/kotlin/gradlew
@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"
diff --git a/samples/openapi3/client/petstore/kotlin/gradlew.bat b/samples/openapi3/client/petstore/kotlin/gradlew.bat
new file mode 100644
index 000000000000..e95643d6a2ca
--- /dev/null
+++ b/samples/openapi3/client/petstore/kotlin/gradlew.bat
@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/.openapi-generator/VERSION b/samples/server/openapi3/petstore/kotlin-springboot/.openapi-generator/VERSION
index 6d94c9c2e12a..afa636560641 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/.openapi-generator/VERSION
+++ b/samples/server/openapi3/petstore/kotlin-springboot/.openapi-generator/VERSION
@@ -1 +1 @@
-3.3.0-SNAPSHOT
\ No newline at end of file
+4.0.0-SNAPSHOT
\ No newline at end of file
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApi.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApi.kt
new file mode 100644
index 000000000000..4ca16d903e4f
--- /dev/null
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApi.kt
@@ -0,0 +1,46 @@
+package org.openapitools.api
+
+import org.openapitools.model.SysMailFormData
+import io.swagger.annotations.*
+import org.springframework.http.HttpStatus
+import org.springframework.http.MediaType
+import org.springframework.http.ResponseEntity
+import org.springframework.stereotype.Controller
+import org.springframework.web.bind.annotation.RequestBody
+import org.springframework.web.bind.annotation.RequestPart
+import org.springframework.web.bind.annotation.RequestParam
+import org.springframework.web.bind.annotation.PathVariable
+import org.springframework.web.bind.annotation.RequestHeader
+import org.springframework.web.bind.annotation.RequestMethod
+import org.springframework.web.bind.annotation.RequestMapping
+import org.springframework.validation.annotation.Validated
+import org.springframework.web.context.request.NativeWebRequest
+import org.springframework.web.multipart.MultipartFile
+import org.springframework.beans.factory.annotation.Autowired
+
+import javax.validation.Valid
+import javax.validation.constraints.*
+
+import kotlin.collections.List
+import kotlin.collections.Map
+
+@Controller
+@Validated
+@Api(value = "Default", description = "The Default API")
+@RequestMapping("\${api.base-path:/v2}")
+class DefaultApiController(@Autowired(required = true) val service: DefaultApiService) {
+
+    @ApiOperation(
+            value = "",
+            nickname = "updateSysMailAtKey",
+            notes = "Update SysMail template")
+    @ApiResponses(
+            value = [ApiResponse(code = 200, message = "OK")])
+    @RequestMapping(
+            value = ["/sysmails/{key}"],
+            consumes = ["application/json"],
+            method = [RequestMethod.PUT])
+    fun updateSysMailAtKey(@ApiParam(value = "", required=true, defaultValue="null") @PathVariable("key") key: String,@ApiParam(value = "" ,required=true ) @Valid @RequestBody sysMailFormData: SysMailFormData): ResponseEntity<Unit> {
+        return ResponseEntity(service.updateSysMailAtKey(key, sysMailFormData), HttpStatus.OK)
+    }
+}
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiService.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiService.kt
new file mode 100644
index 000000000000..3fe465cfcb07
--- /dev/null
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiService.kt
@@ -0,0 +1,8 @@
+package org.openapitools.api
+
+import org.openapitools.model.SysMailFormData
+
+interface DefaultApiService {
+
+    fun updateSysMailAtKey(key: String,sysMailFormData: SysMailFormData): Unit
+}
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiServiceImpl.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiServiceImpl.kt
new file mode 100644
index 000000000000..a8dffc147772
--- /dev/null
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/DefaultApiServiceImpl.kt
@@ -0,0 +1,12 @@
+package org.openapitools.api
+
+import org.openapitools.model.SysMailFormData
+import org.springframework.stereotype.Service
+
+@Service
+class DefaultApiServiceImpl : DefaultApiService {
+
+    override fun updateSysMailAtKey(key: String,sysMailFormData: SysMailFormData): Unit {
+        TODO("Implement me")
+    }
+}
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApi.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApi.kt
index 17b87c74fdfb..0a3515cb1ca6 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApi.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApi.kt
@@ -56,7 +56,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
     @RequestMapping(
             value = ["/pet/{petId}"],
             method = [RequestMethod.DELETE])
-    fun deletePet(@ApiParam(value = "Pet id to delete", required=true) @PathVariable("petId") petId: Long,@ApiParam(value = "" ) @RequestHeader(value="api_key", required=false) apiKey: String?): ResponseEntity<Unit> {
+    fun deletePet(@ApiParam(value = "Pet id to delete", required=true, defaultValue="null") @PathVariable("petId") petId: Long,@ApiParam(value = "" , defaultValue="null") @RequestHeader(value="api_key", required=false) apiKey: String): ResponseEntity<Unit> {
         return ResponseEntity(service.deletePet(petId, apiKey), HttpStatus.OK)
     }
 
@@ -73,7 +73,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
             value = ["/pet/findByStatus"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun findPetsByStatus(@NotNull @ApiParam(value = "Status values that need to be considered for filter", required = true, allowableValues = "available, pending, sold") @Valid @RequestParam(value = "status", required = true) status: List<String>): ResponseEntity<List<Pet>> {
+    fun findPetsByStatus(@NotNull @ApiParam(value = "Status values that need to be considered for filter", required = true, allowableValues = "available, pending, sold", defaultValue = "null") @Valid @RequestParam(value = "status", required = true, defaultValue="null") status: List<String>): ResponseEntity<List<Pet>> {
         return ResponseEntity(service.findPetsByStatus(status), HttpStatus.OK)
     }
 
@@ -90,7 +90,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
             value = ["/pet/findByTags"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun findPetsByTags(@NotNull @ApiParam(value = "Tags to filter by", required = true) @Valid @RequestParam(value = "tags", required = true) tags: List<String>): ResponseEntity<List<Pet>> {
+    fun findPetsByTags(@NotNull @ApiParam(value = "Tags to filter by", required = true, defaultValue = "null") @Valid @RequestParam(value = "tags", required = true, defaultValue="null") tags: List<String>): ResponseEntity<List<Pet>> {
         return ResponseEntity(service.findPetsByTags(tags), HttpStatus.OK)
     }
 
@@ -106,7 +106,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
             value = ["/pet/{petId}"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun getPetById(@ApiParam(value = "ID of pet to return", required=true) @PathVariable("petId") petId: Long): ResponseEntity<Pet> {
+    fun getPetById(@ApiParam(value = "ID of pet to return", required=true, defaultValue="null") @PathVariable("petId") petId: Long): ResponseEntity<Pet> {
         return ResponseEntity(service.getPetById(petId), HttpStatus.OK)
     }
 
@@ -136,7 +136,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
             value = ["/pet/{petId}"],
             consumes = ["application/x-www-form-urlencoded"],
             method = [RequestMethod.POST])
-    fun updatePetWithForm(@ApiParam(value = "ID of pet that needs to be updated", required=true) @PathVariable("petId") petId: Long,@ApiParam(value = "Updated name of the pet", defaultValue="null") @RequestParam(value="name", required=false) name: String ,@ApiParam(value = "Updated status of the pet", defaultValue="null") @RequestParam(value="status", required=false) status: String ): ResponseEntity<Unit> {
+    fun updatePetWithForm(@ApiParam(value = "ID of pet that needs to be updated", required=true, defaultValue="null") @PathVariable("petId") petId: Long,@ApiParam(value = "Updated name of the pet", defaultValue="null") @RequestParam(value="name", required=false) name: String ,@ApiParam(value = "Updated status of the pet", defaultValue="null") @RequestParam(value="status", required=false) status: String ): ResponseEntity<Unit> {
         return ResponseEntity(service.updatePetWithForm(petId, name, status), HttpStatus.OK)
     }
 
@@ -153,7 +153,7 @@ class PetApiController(@Autowired(required = true) val service: PetApiService) {
             produces = ["application/json"], 
             consumes = ["multipart/form-data"],
             method = [RequestMethod.POST])
-    fun uploadFile(@ApiParam(value = "ID of pet to update", required=true) @PathVariable("petId") petId: Long,@ApiParam(value = "Additional data to pass to server", defaultValue="null") @RequestParam(value="additionalMetadata", required=false) additionalMetadata: String ,@ApiParam(value = "file detail") @Valid @RequestPart("file") file: MultipartFile): ResponseEntity<ModelApiResponse> {
+    fun uploadFile(@ApiParam(value = "ID of pet to update", required=true, defaultValue="null") @PathVariable("petId") petId: Long,@ApiParam(value = "Additional data to pass to server", defaultValue="null") @RequestParam(value="additionalMetadata", required=false) additionalMetadata: String ,@ApiParam(value = "file detail") @Valid @RequestPart("file") file: MultipartFile): ResponseEntity<ModelApiResponse> {
         return ResponseEntity(service.uploadFile(petId, additionalMetadata, file), HttpStatus.OK)
     }
 }
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiService.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiService.kt
index b31d96e91b73..c2e81c4c66b6 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiService.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiService.kt
@@ -7,7 +7,7 @@ interface PetApiService {
 
     fun addPet(pet: Pet): Unit
 
-    fun deletePet(petId: Long,apiKey: String?): Unit
+    fun deletePet(petId: Long,apiKey: String): Unit
 
     fun findPetsByStatus(status: List<String>): List<Pet>
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiServiceImpl.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiServiceImpl.kt
index 80b7d6e8fe1c..86ae8e063208 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiServiceImpl.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/PetApiServiceImpl.kt
@@ -11,7 +11,7 @@ class PetApiServiceImpl : PetApiService {
         TODO("Implement me")
     }
 
-    override fun deletePet(petId: Long,apiKey: String?): Unit {
+    override fun deletePet(petId: Long,apiKey: String): Unit {
         TODO("Implement me")
     }
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/StoreApi.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/StoreApi.kt
index f277e8089065..6931bd2500c7 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/StoreApi.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/StoreApi.kt
@@ -39,7 +39,7 @@ class StoreApiController(@Autowired(required = true) val service: StoreApiServic
     @RequestMapping(
             value = ["/store/order/{orderId}"],
             method = [RequestMethod.DELETE])
-    fun deleteOrder(@ApiParam(value = "ID of the order that needs to be deleted", required=true) @PathVariable("orderId") orderId: String): ResponseEntity<Unit> {
+    fun deleteOrder(@ApiParam(value = "ID of the order that needs to be deleted", required=true, defaultValue="null") @PathVariable("orderId") orderId: String): ResponseEntity<Unit> {
         return ResponseEntity(service.deleteOrder(orderId), HttpStatus.OK)
     }
 
@@ -71,7 +71,7 @@ class StoreApiController(@Autowired(required = true) val service: StoreApiServic
             value = ["/store/order/{orderId}"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun getOrderById(@Min(1L) @Max(5L) @ApiParam(value = "ID of pet that needs to be fetched", required=true) @PathVariable("orderId") orderId: Long): ResponseEntity<Order> {
+    fun getOrderById(@Min(1L) @Max(5L) @ApiParam(value = "ID of pet that needs to be fetched", required=true, defaultValue="null") @PathVariable("orderId") orderId: Long): ResponseEntity<Order> {
         return ResponseEntity(service.getOrderById(orderId), HttpStatus.OK)
     }
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/UserApi.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/UserApi.kt
index 6822bccecafa..aff695572ada 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/UserApi.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/api/UserApi.kt
@@ -81,7 +81,7 @@ class UserApiController(@Autowired(required = true) val service: UserApiService)
     @RequestMapping(
             value = ["/user/{username}"],
             method = [RequestMethod.DELETE])
-    fun deleteUser(@ApiParam(value = "The name that needs to be deleted", required=true) @PathVariable("username") username: String): ResponseEntity<Unit> {
+    fun deleteUser(@ApiParam(value = "The name that needs to be deleted", required=true, defaultValue="null") @PathVariable("username") username: String): ResponseEntity<Unit> {
         return ResponseEntity(service.deleteUser(username), HttpStatus.OK)
     }
 
@@ -96,7 +96,7 @@ class UserApiController(@Autowired(required = true) val service: UserApiService)
             value = ["/user/{username}"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun getUserByName(@ApiParam(value = "The name that needs to be fetched. Use user1 for testing.", required=true) @PathVariable("username") username: String): ResponseEntity<User> {
+    fun getUserByName(@ApiParam(value = "The name that needs to be fetched. Use user1 for testing.", required=true, defaultValue="null") @PathVariable("username") username: String): ResponseEntity<User> {
         return ResponseEntity(service.getUserByName(username), HttpStatus.OK)
     }
 
@@ -111,7 +111,7 @@ class UserApiController(@Autowired(required = true) val service: UserApiService)
             value = ["/user/login"],
             produces = ["application/xml", "application/json"], 
             method = [RequestMethod.GET])
-    fun loginUser(@NotNull @ApiParam(value = "The user name for login", required = true) @Valid @RequestParam(value = "username", required = true) username: String,@NotNull @ApiParam(value = "The password for login in clear text", required = true) @Valid @RequestParam(value = "password", required = true) password: String): ResponseEntity<String> {
+    fun loginUser(@NotNull @ApiParam(value = "The user name for login", required = true, defaultValue = "null") @Valid @RequestParam(value = "username", required = true, defaultValue="null") username: String,@NotNull @ApiParam(value = "The password for login in clear text", required = true, defaultValue = "null") @Valid @RequestParam(value = "password", required = true, defaultValue="null") password: String): ResponseEntity<String> {
         return ResponseEntity(service.loginUser(username, password), HttpStatus.OK)
     }
 
@@ -138,7 +138,7 @@ class UserApiController(@Autowired(required = true) val service: UserApiService)
             value = ["/user/{username}"],
             consumes = ["application/json"],
             method = [RequestMethod.PUT])
-    fun updateUser(@ApiParam(value = "name that need to be deleted", required=true) @PathVariable("username") username: String,@ApiParam(value = "Updated user object" ,required=true ) @Valid @RequestBody user: User): ResponseEntity<Unit> {
+    fun updateUser(@ApiParam(value = "name that need to be deleted", required=true, defaultValue="null") @PathVariable("username") username: String,@ApiParam(value = "Updated user object" ,required=true ) @Valid @RequestBody user: User): ResponseEntity<Unit> {
         return ResponseEntity(service.updateUser(username, user), HttpStatus.OK)
     }
 }
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Category.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Category.kt
index da259e87b8e5..c34cec48df16 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Category.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Category.kt
@@ -13,10 +13,10 @@ import io.swagger.annotations.ApiModelProperty
  */
 data class Category (
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("id") val id: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("name") val name: String? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject.kt
similarity index 70%
rename from samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body.kt
rename to samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject.kt
index df03586b3835..3a1526a0db77 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject.kt
@@ -11,12 +11,12 @@ import io.swagger.annotations.ApiModelProperty
  * @param name Updated name of the pet
  * @param status Updated status of the pet
  */
-data class Body (
+data class InlineObject (
 
-        @ApiModelProperty(value = "Updated name of the pet")
+        @ApiModelProperty(example = "null", value = "Updated name of the pet")
         @JsonProperty("name") val name: String? = null,
 
-        @ApiModelProperty(value = "Updated status of the pet")
+        @ApiModelProperty(example = "null", value = "Updated status of the pet")
         @JsonProperty("status") val status: String? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body1.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject1.kt
similarity index 72%
rename from samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body1.kt
rename to samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject1.kt
index 1e95e248d1cb..4600798bc9a1 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Body1.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/InlineObject1.kt
@@ -11,12 +11,12 @@ import io.swagger.annotations.ApiModelProperty
  * @param additionalMetadata Additional data to pass to server
  * @param file file to upload
  */
-data class Body1 (
+data class InlineObject1 (
 
-        @ApiModelProperty(value = "Additional data to pass to server")
+        @ApiModelProperty(example = "null", value = "Additional data to pass to server")
         @JsonProperty("additionalMetadata") val additionalMetadata: String? = null,
 
-        @ApiModelProperty(value = "file to upload")
+        @ApiModelProperty(example = "null", value = "file to upload")
         @JsonProperty("file") val file: java.io.File? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/ModelApiResponse.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/ModelApiResponse.kt
index e933f2436a43..17697fdfe8d4 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/ModelApiResponse.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/ModelApiResponse.kt
@@ -14,13 +14,13 @@ import io.swagger.annotations.ApiModelProperty
  */
 data class ModelApiResponse (
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("code") val code: Int? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("type") val type: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("message") val message: String? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Order.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Order.kt
index e1065f56bd32..be8e2f33fb37 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Order.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Order.kt
@@ -18,22 +18,22 @@ import io.swagger.annotations.ApiModelProperty
  */
 data class Order (
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("id") val id: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("petId") val petId: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("quantity") val quantity: Int? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("shipDate") val shipDate: java.time.OffsetDateTime? = null,
 
-        @ApiModelProperty(value = "Order Status")
+        @ApiModelProperty(example = "null", value = "Order Status")
         @JsonProperty("status") val status: Order.Status? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("complete") val complete: Boolean? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Pet.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Pet.kt
index 967bd0846b6e..80af728b7e49 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Pet.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Pet.kt
@@ -25,19 +25,19 @@ data class Pet (
         @JsonProperty("name") val name: String,
 
         @get:NotNull 
-        @ApiModelProperty(required = true, value = "")
+        @ApiModelProperty(example = "null", required = true, value = "")
         @JsonProperty("photoUrls") val photoUrls: List<String>,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("id") val id: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("category") val category: Category? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("tags") val tags: List<Tag>? = null,
 
-        @ApiModelProperty(value = "pet status in the store")
+        @ApiModelProperty(example = "null", value = "pet status in the store")
         @JsonProperty("status") val status: Pet.Status? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/SysMailFormData.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/SysMailFormData.kt
new file mode 100644
index 000000000000..456a5ac13c3f
--- /dev/null
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/SysMailFormData.kt
@@ -0,0 +1,24 @@
+package org.openapitools.model
+
+import java.util.Objects
+import com.fasterxml.jackson.annotation.JsonProperty
+import javax.validation.Valid
+import javax.validation.constraints.*
+import io.swagger.annotations.ApiModelProperty
+
+/**
+ * Data to update a SysMail template.
+ * @param subject 
+ * @param body 
+ */
+data class SysMailFormData (
+
+        @ApiModelProperty(example = "null", value = "")
+        @JsonProperty("subject") val subject: String? = null,
+
+        @ApiModelProperty(example = "null", value = "")
+        @JsonProperty("body") val body: String? = null
+) {
+
+}
+
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Tag.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Tag.kt
index e40833c55fd0..70c706d00a6e 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Tag.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/Tag.kt
@@ -13,10 +13,10 @@ import io.swagger.annotations.ApiModelProperty
  */
 data class Tag (
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("id") val id: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("name") val name: String? = null
 ) {
 
diff --git a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/User.kt b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/User.kt
index b9cc2886ea09..4cfaf0988746 100644
--- a/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/User.kt
+++ b/samples/server/openapi3/petstore/kotlin-springboot/src/main/kotlin/org/openapitools/model/User.kt
@@ -19,28 +19,28 @@ import io.swagger.annotations.ApiModelProperty
  */
 data class User (
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("id") val id: Long? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("username") val username: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("firstName") val firstName: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("lastName") val lastName: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("email") val email: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("password") val password: String? = null,
 
-        @ApiModelProperty(value = "")
+        @ApiModelProperty(example = "null", value = "")
         @JsonProperty("phone") val phone: String? = null,
 
-        @ApiModelProperty(value = "User Status")
+        @ApiModelProperty(example = "null", value = "User Status")
         @JsonProperty("userStatus") val userStatus: Int? = null
 ) {
 
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/api/openapi.yaml b/samples/server/petstore/rust-server/output/rust-server-test/api/openapi.yaml
index ed356b28eb0a..b2b215809d00 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/api/openapi.yaml
+++ b/samples/server/petstore/rust-server/output/rust-server-test/api/openapi.yaml
@@ -91,6 +91,7 @@ components:
         '*/*':
           schema:
             $ref: '#/components/schemas/inline_object'
+      required: true
   schemas:
     additionalPropertiesObject:
       additionalProperties:
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/examples/client.rs b/samples/server/petstore/rust-server/output/rust-server-test/examples/client.rs
index 54377a219dc1..d43e0fea7f93 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/examples/client.rs
+++ b/samples/server/petstore/rust-server/output/rust-server-test/examples/client.rs
@@ -33,7 +33,6 @@ fn main() {
             .help("Sets the operation to run")
             .possible_values(&[
     "DummyGet",
-    "DummyPut",
     "FileResponseGet",
     "HtmlPost",
     "RawJsonGet",
@@ -82,10 +81,11 @@ fn main() {
             println!("{:?} (X-Span-ID: {:?})", result, (client.context() as &Has<XSpanIdString>).get().clone());
          },
 
-        Some("DummyPut") => {
-            let result = core.run(client.dummy_put(None));
-            println!("{:?} (X-Span-ID: {:?})", result, (client.context() as &Has<XSpanIdString>).get().clone());
-         },
+        // Disabled because there's no example.
+        // Some("DummyPut") => {
+        //     let result = core.run(client.dummy_put(???));
+        //     println!("{:?} (X-Span-ID: {:?})", result, (client.context() as &Has<XSpanIdString>).get().clone());
+        //  },
 
         Some("FileResponseGet") => {
             let result = core.run(client.file_response_get());
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/examples/server_lib/server.rs b/samples/server/petstore/rust-server/output/rust-server-test/examples/server_lib/server.rs
index b9c7cfba79fc..38aa0d05c4e0 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/examples/server_lib/server.rs
+++ b/samples/server/petstore/rust-server/output/rust-server-test/examples/server_lib/server.rs
@@ -40,7 +40,7 @@ impl<C> Api<C> for Server<C> where C: Has<XSpanIdString>{
     }
 
 
-    fn dummy_put(&self, nested_response: Option<models::InlineObject>, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
+    fn dummy_put(&self, nested_response: models::InlineObject, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
         let context = context.clone();
         println!("dummy_put({:?}) - X-Span-ID: {:?}", nested_response, context.get().0.clone());
         Box::new(futures::failed("Generic failure".into()))
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/src/client/mod.rs b/samples/server/petstore/rust-server/output/rust-server-test/src/client/mod.rs
index c9c1c1169b88..5e3ae082ccf0 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/src/client/mod.rs
+++ b/samples/server/petstore/rust-server/output/rust-server-test/src/client/mod.rs
@@ -306,7 +306,7 @@ impl<F, C> Api<C> for Client<F> where
 
     }
 
-    fn dummy_put(&self, param_nested_response: Option<models::InlineObject>, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
+    fn dummy_put(&self, param_nested_response: models::InlineObject, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
 
 
         let uri = format!(
@@ -321,14 +321,12 @@ impl<F, C> Api<C> for Client<F> where
 
         let mut request = hyper::Request::new(hyper::Method::Put, uri);
 
-        let body = param_nested_response.map(|ref body| {
 
-            serde_json::to_string(body).expect("impossible to fail to serialize")
-        });
+        let body = serde_json::to_string(&param_nested_response).expect("impossible to fail to serialize");
+
+
+        request.set_body(body.into_bytes());
 
-if let Some(body) = body {
-            request.set_body(body.into_bytes());
-        }
 
         request.headers_mut().set(ContentType(mimetypes::requests::DUMMY_PUT.clone()));
         request.headers_mut().set(XSpanId((context as &Has<XSpanIdString>).get().0.clone()));
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/src/lib.rs b/samples/server/petstore/rust-server/output/rust-server-test/src/lib.rs
index efae712e4ccb..5f9e44062b09 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/src/lib.rs
+++ b/samples/server/petstore/rust-server/output/rust-server-test/src/lib.rs
@@ -77,7 +77,7 @@ pub trait Api<C> {
     fn dummy_get(&self, context: &C) -> Box<Future<Item=DummyGetResponse, Error=ApiError>>;
 
 
-    fn dummy_put(&self, nested_response: Option<models::InlineObject>, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>>;
+    fn dummy_put(&self, nested_response: models::InlineObject, context: &C) -> Box<Future<Item=DummyPutResponse, Error=ApiError>>;
 
     /// Get a file
     fn file_response_get(&self, context: &C) -> Box<Future<Item=FileResponseGetResponse, Error=ApiError>>;
@@ -97,7 +97,7 @@ pub trait ApiNoContext {
     fn dummy_get(&self) -> Box<Future<Item=DummyGetResponse, Error=ApiError>>;
 
 
-    fn dummy_put(&self, nested_response: Option<models::InlineObject>) -> Box<Future<Item=DummyPutResponse, Error=ApiError>>;
+    fn dummy_put(&self, nested_response: models::InlineObject) -> Box<Future<Item=DummyPutResponse, Error=ApiError>>;
 
     /// Get a file
     fn file_response_get(&self) -> Box<Future<Item=FileResponseGetResponse, Error=ApiError>>;
@@ -130,7 +130,7 @@ impl<'a, T: Api<C>, C> ApiNoContext for ContextWrapper<'a, T, C> {
     }
 
 
-    fn dummy_put(&self, nested_response: Option<models::InlineObject>) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
+    fn dummy_put(&self, nested_response: models::InlineObject) -> Box<Future<Item=DummyPutResponse, Error=ApiError>> {
         self.api().dummy_put(nested_response, &self.context())
     }
 
diff --git a/samples/server/petstore/rust-server/output/rust-server-test/src/server/mod.rs b/samples/server/petstore/rust-server/output/rust-server-test/src/server/mod.rs
index a889c6b85d04..3a9ba4b43c97 100644
--- a/samples/server/petstore/rust-server/output/rust-server-test/src/server/mod.rs
+++ b/samples/server/petstore/rust-server/output/rust-server-test/src/server/mod.rs
@@ -202,13 +202,16 @@ where
                                             unused_elements.push(path.to_string());
                                     }) {
                                         Ok(param_nested_response) => param_nested_response,
-
-                                        Err(_) => None,
+                                        Err(e) => return Box::new(future::ok(Response::new().with_status(StatusCode::BadRequest).with_body(format!("Couldn't parse body parameter nested_response - doesn't match schema: {}", e)))),
                                     }
 
                                 } else {
                                     None
                                 };
+                                let param_nested_response = match param_nested_response {
+                                    Some(param_nested_response) => param_nested_response,
+                                    None => return Box::new(future::ok(Response::new().with_status(StatusCode::BadRequest).with_body("Missing required body parameter nested_response"))),
+                                };
 
 
                                 Box::new(api_impl.dummy_put(param_nested_response, &context)