Themeleaf: How to display a default message on a page?

Question

Spring

Good evening!
Such a question, when the model is displayed on the html page, and there is no data, I would like what would be written in the tag - "no data" can this be done on the page itself without resorting to adding an attribute in the controller?
Example:

<span th:text="'Your city : ' + ${address.city}">Non data</span>

I was hoping that if address.city == null then Non data, if not, then the data from the model, but it's not...
Another question, how is this usually done?
Thank you.

Answer 1

Hello!
Why don't you use the capabilities of the template engine?
Here are a few options for solving the issue:
1) Using the ternary operator

<span th:text="${address.city != null} ? ${address.city} : 'No data!'">City</span>

2) Usage: if unless (similar to if else in java). Note that if city is a string, then you can use ==, and if it's an object, then you need to useeq

<span th:if="${address.city} == null">Non data</span>
<span th:unless="${address.city} != null" th:text="'Your city : ' + ${address.city}">Non data</span>

Also note that you can "secure" the application if the value is null using the secure navigation operator ?.between address & city

<span th:text="'Your city : ' + ${address?.city}">Non data</span>