How to check isEmpty on a List of Lists in Thymeleaf?

问题

I have the following:

@Data
public class SomeClass {
   List<SomeBean> beans = new ArrayList();
}

If I have a List of SomeClass beans, is there an easy way to check whether the beans list is empty?

For example, something like this doesn't work (logically): th:if="${#lists.isEmpty(someClass?.beans)}"

Perhaps a utility that can flatten the lists?

I could instead put this on the server-side, but didn't know whether there was an easy way to do it on the front-end.

回答1:

For these kinds of things, look at collection selection and collection projection. In your case an expression like this should work:

th:if="${#aggregates.sum(listOfSomeClass.![beans.size()]) == 0}"

来源：https://stackoverflow.com/questions/63623608/how-to-check-isempty-on-a-list-of-lists-in-thymeleaf