template creatiion and required type 'java.util.List' error

I create a Template an DataFields object in html, but I cannot send this template object to the controller. It sends the object as a Json list, but the controller must receive it as a java list.

Failed to convert value of type 'java.lang.String' to required type 'java.util.List'; For input string: "[1,2,3]"
org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.util.List'; For input string: "[1,2,3]"
at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.convertIfNecessary(AbstractNamedValueMethodArgumentResolver.java:302)