Java – Thymeleaf: check if a variable is defined

javaspringspring-bootspring-mvcthymeleaf

How can I check if a variable is defined in Thymeleaf?

Something like this in Javascript:

if (typeof variable !== 'undefined') { }

or this in PHP:

if (isset($var)) { }

Is there an equivalent in Thymeleaf?

Best Solution

Yes, you can easily check if given property exists for your document using following code. Note, that you're creating div tag if condition is met:

<div th:if="${variable != null}" th:text="Yes, variable exists!">
   I wonder, if variable exists...
</div>

If you want using variable's field it's worth checking if this field exists as well

<div th:if="${variable != null && variable.name != null}" th:text="${variable.name}">
   I wonder, if variable.name exists...
</div>

Or even shorter, without using if statement

<div th:text="${variable?.name}">
   I wonder, if variable.name exists...
</div>`

But using this statement you will end creating div tag whether variable or variable.name exist

You can learn more about conditionals in thymeleaf here

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