How to do if-else in Thymeleaf?

Question

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:
http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#local-variables