STRUTS ParameterInterceptor and ValidationInterceptor interceptors don't offer a good solution for this problem : the only solution is to migrate the validation annotations to declare validation rules in an XML file (but there will be a lot of code duplication in this case) or coding rules by hand in a validate method.
In our application, we found this trick but this is not elegant : we added a new interceptor ValidationFilterInterceptor that calls a method dynamically actionMethodValidationFilter (if the action method id actionMethod, the validationFilterInterceptor will call actionMethodValidationFilter) where we remove the "bad" errors (something like this : setFieldErrors(filterFieldErrorsOn("data2", getFieldErrors())));
1. to add a new Annotation @ValidationCase(name="case1") that applies on the action method
2. to add a new parameter validationCase in all Validation annotation ex : @RequiredValidator(key = "validation.required", validationCase=
3. to take into account in ParameterInterceptor and ValidationInterceptor, this annotation and new parameter in existing annotations to add conversion/validation rules only for the annotation linked to the "current" validation case.