How to Do If-Else in Thymeleaf?
What's the Best Way to Do a Simple If-Else in Thymeleaf? I Want to Achieve in Thymeleaf the Same Effect as Hello! Something Else in Jstl. What I've Figured So...
What's the best way to do a simple if-else in Thymeleaf?
I want to achieve in Thymeleaf the same effect as
<c:choose>
<c:when test="${potentially_complex_expression}">
<h2>Hello!</h2>
</c:when>
<c:otherwise>
<span class="xxx">Something else</span>
</c:otherwise>
</c:choose>
in JSTL.
What I've figured so far:
<div th:with="condition=${potentially_complex_expression}" th:remove="tag">
<h2 th:if="${condition}">Hello!</h2>
<span th:unless="${condition}" class="xxx">Something else</span>
</div>
I don't want to evaluate potentially_complex_expression twice. That's why I introduced local variable condition. Still I don't like using both th:if="${condition} and th:unless="${condition}".
An important thing is that I use two different HTML tags: let's say h2 and span.
Can you suggest a better way to achieve it?
12 Answers
Thymeleaf has an equivalent to <c:choose> and <c:when>: the th:switch and th:case attributes introduced in Thymeleaf 2.0.
They work as you'd expect, using * for the default case:
<div th:switch="${user.role}">
<p th:case="'admin'">User is an administrator</p>
<p th:case="#{roles.manager}">User is a manager</p>
<p th:case="*">User is some other thing</p>
</div>
See this for a quick explanation of syntax (or the Thymeleaf tutorials).
Disclaimer: As required by StackOverflow rules, I'm the author of Thymeleaf.
I tried this code to find out if a customer is logged in or anonymous. I did using the th:if and th:unless conditional expressions. Pretty simple way to do it.
<!-- IF CUSTOMER IS ANONYMOUS -->
<div th:if="${customer.anonymous}">
<div>Welcome, Guest</div>
</div>
<!-- ELSE -->
<div th:unless="${customer.anonymous}">
<div th:text=" 'Hi,' + ${customer.name}">Hi, User</div>
</div>
I'd like to share my example related to security in addition to Daniel Fernández.
<div th:switch="${#authentication}? ${#authorization.expression('isAuthenticated()')} : ${false}">
<span th:case="${false}">User is not logged in</span>
<span th:case="${true}">Logged in user</span>
<span th:case="*">Should never happen, but who knows...</span>
</div>
Here is complex expression with mixed 'authentication' and 'authorization' utility objects which produces 'true/false' result for thymeleaf template code.
The 'authentication' and 'authorization' utility objects came from thymeleaf extras springsecurity3 library. When 'authentication' object is not available OR authorization.expression('isAuthenticated()') evaluates to 'false', expression returns ${false}, otherwise ${true}.
You can use
If-then-else: (if) ? (then) : (else)
Example:
'User is of type ' + (${user.isAdmin()} ? 'Administrator' : (${user.type} ?: 'Unknown'))
It could be useful for the new people asking the same question.
Another solution - you can use local variable:
<div th:with="expr_result = ${potentially_complex_expression}">
<div th:if="${expr_result}">
<h2>Hello!</h2>
</div>
<div th:unless="${expr_result}">
<span class="xxx">Something else</span>
</div>
</div>
More about local variables:
In simpler case (when html tags is the same):
<h2 th:text="${potentially_complex_expression} ? 'Hello' : 'Something else'">/h2>
Another solution is just using not to get the opposite negation:
<h2 th:if="${potentially_complex_expression}">Hello!</h2>
<span class="xxx" th:if="${not potentially_complex_expression}">Something else</span>
As explained in the documentation, it's the same thing as using th:unless. As other answers have explained:
Also,
th:ifhas an inverse attribute,th:unless, which we could have used in the previous example instead of using a not inside the OGNL expression
Using not also works, but IMHO it is more readable to use th:unless instead of negating the condition with not.
Use th:switch as an if-else
<span th:switch="${isThisTrue}">
<i th:case="true" class="fas fa-check green-text"></i>
<i th:case="false" class="fas fa-times red-text"></i>
</span>
Elena Rostova holds a Master's degree in Public Health Journalism. She covers groundbreaking medical research, holistic wellness trends, mental health awareness, and nutritional science.
