[Java][Spring] fix unhandledException not working in combination with… (#9879)

* #4393 fix unhandledException not working in combination with skipDefaultInterface

* generate samples

samples/server/petstore/spring-boot-defaultInterface-unhandledException/README.md

@@ -0,0 +1,27 @@
+
+# OpenAPI generated API stub
+
+Spring Framework stub
+
+
+## Overview
+This code was generated by the [OpenAPI Generator](https://openapi-generator.tech) project.
+By using the [OpenAPI-Spec](https://openapis.org), you can easily generate an API stub.
+This is an example of building API stub interfaces in Java using the Spring framework.
+
+The stubs generated can be used in your existing Spring-MVC or Spring-Boot application to create controller endpoints
+by adding ```@Controller``` classes that implement the interface. Eg:
+```java
+@Controller
+public class PetController implements PetApi {
+// implement all PetApi methods
+}
+```
+
+You can also use the interface to create [Spring-Cloud Feign clients](http://projects.spring.io/spring-cloud/spring-cloud.html#spring-cloud-feign-inheritance).Eg:
+```java
+@FeignClient(name="pet", url="http://petstore.swagger.io/v2")
+public interface PetClient extends PetApi {
+
+}
+```