fix mapper.copy()

Author: thorstenhirsch

modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache

@@ -297,12 +297,17 @@ public class ApiClient {
   }
 
   /**
-   * Get a copy of the current {@link ObjectMapper}.
+   * Get {{^useJackson3}}a copy of {{/useJackson3}}the current {@link ObjectMapper}.
    *
-   * @return A copy of the current object mapper.
+   * @return {{^useJackson3}}A copy of the current{{/useJackson3}}{{#useJackson3}}The current{{/useJackson3}} object mapper.
    */
   public ObjectMapper getObjectMapper() {
+{{^useJackson3}}
     return mapper.copy();
+{{/useJackson3}}
+{{#useJackson3}}
+    return mapper;
+{{/useJackson3}}
   }
 
   /**