java - Thymeleaf Error for <input> date with th:pattern -

i'm trying use th:pattern date input form field following thymeleaf template using spring-mvc without luck. else experienced similar thing , has insight or alternative?

i tried 1. hard-coding pattern

<input type="text" th:pattern="mm/dd/yyyy" th:field="*{classdate}"/>

received error:

request processing failed; nested exception org.thymeleaf.exceptions.templateprocessingexception: not parse expression: "mm/dd/yyyy"  

and 2. setting pattern in java code template use

<input type="date" th:pattern="${classdate_format}" th:field="*{classdate}"/>

received error:

request processing failed; nested exception org.thymeleaf.exceptions.templateprocessingexception: error during execution of processor 'org.thymeleaf.spring3.processor.attr.springinputgeneralfieldattrprocessor' 

pattern html5 attribute of input tag.

pattern validates input value using regex. value, inserts pattern attribute should correct regex pattern.

if using thymeleaf's th: prefix, template processor trying find appropriate variable in spiring's model , insert value of attribute. thymeleaf using spring el it's templates.

so first approach incorrect because of using invalid springel expression.

the second solution looks better, type="date" gives want, works not browsers. ${classdate_format} looks correct expression. understand causes second error more code needed.

anyway there reason use th: prefix pattern attribute? needed if want create regex pattern dynamically @ server side. in case regex pattern pretty straightforward, can use attribute without th:. write correct regex case please refer this answer.