Thymeleaf - getting locale and comparing - thymeleaf

Question

The below should set h1 to HOWDY as the locale is showing en_GB, but it doesn't fall into the case?
Am I doing something wrong here? Thanks
<h1 th:text="${#locale}"></h1>
<div th:switch="${#locale}">
<h1 th:case="'en_GB'">HOWDY</h1>
</div>

Answer 1

When you use Thymeleaf's #locale, you are using a reference to a Java Locale object.
What Works?
The following works the way you expect, because it has already evaluated the Java locale object to its string representation, before evaluating each case statement:
<div th:switch="${#locale.toString()}">
<h1 th:case="'en_GB'">HOWDY</h1>
</div>
The following also works:
<div th:switch="__${#locale}__">
<h1 th:case="'en_GB'">HOWDY</h1>
</div>
In this case, it works because you are using the Thymeleaf preprocessor syntax __${...}__ to force Thymeleaf to evaluate #locale (to its string representation) before it evaluates the remainder of the switch statement.
Additional Explanation
Because Thymeleaf's #locale represents a Java Locale object, you can use any of Locales suitable fields and methods, such as :
<div th:text="${#locale.country}"></div> <!-- a field -->
<div th:text="${#locale.toLanguageTag()}"></div> <!-- a method -->
This is why only using ${#locale} in the Thymeleaf switch statement does not match the 'en_GB' string literal that you are expecting it to match: Thymeleaf is comparing an object to a string.
When you use this...
<div th:text="${#locale}"></div>
...you are again accessing the object itself. But in this case the object will use its toString() method when being rendered by Thymeleaf, before it is displayed - giving you your en_GB displayed value.
However, when you use this...
<div th:switch="${#locale}">
<h1 th:case="'en_GB'">HOWDY</h1>
</div>
...Thymeleaf is using the locale object in the switch statement, not its string representation.