Thymeleaf - Check if array contains element with property

Issue

I have a list of comments. Each comment has an attribute author. And each author has a username.

I want to display a specific button only if the current user did not write a comment yet. (Which means there must be no comment in the list, where the username of the author equals user.username)

This is what it would look like in JavaScript:

if(!comments.some(comment => comment.author.username === user.username))

But I have no idea, how to do it in Thymeleaf. I could not find any necessary functions like array#map(), array#any(), etc. Inline loops also don't seem to be a thing.

 <button th:if="${!<What goes here?>}" class="btn btn-primary">Add Comment</button>

How do I do it?

Solution

Finally found a working solution: https://stackoverflow.com/a/34828280/10686377

Using Spring's Collection Selection you can check if a list contains an element with a specific property value.

<button th:unless="${comments.^[author.username == user.username]}"  class="btn btn-primary">Add Comment</button>

Answered By - FireFuro99