Answer by Greg for how to pass a value using thymeleaf to data of bootstrap?

The following line makes no sense: data-id="th:text="${car.id}""

1. The purpose of th:text is to modify the body text of the element (in this case, a button element). You're trying to set an attribute value.
2. If you want thymeleaf to modify a data attribute like data-id, you need to th:attr instead

That line should be written as follows:

data-id="" th:attr="data-id=${car.id}"

If you want the data-id to have some default value like "example-id", do this:

data-id="example-id" th:attr="data-id=${car.id}"