Thymeleaf/Spring: How to check if a message property exists - spring

Question

Is it possible to check if a message property exists?
Example: I would like to remove a collapsable div-Element in a loop containing only a message property.
<div th:each="payment : ${paymentList}">
<input type="radio" data-toggle="radio-collapse" data-target="#collapse1" [...] /> [...]
<div id="collapse1" th:utext="#{|payment.${payment.id}.additionalInfo|}" [...]>
Hello, world!
</div>
</div>
If there is no additional info for the payment the element is not necessary.
Lets say we have the IDs DIRECT_DEBIT, PAYPAL and SAFERPAY and the following message properties:
payment.DIRECT_DEBIT=Direct debit
payment.DIRECT_DEBIT.additionalInfo=Direct debit info text...
payment.PAYPAL=PayPal
payment.PAYPAL.additionalInfo=PayPal info text...
payment.SAFERPAY=Saferpay
As you can see there is no additionInfo message property for SAFERPAY.

Answer 1

You should use the #messages object to check if a message exists. For example:
th:if="${#messages.msgOrNull('payment.' + payment.id + '.additionalInfo') != null}"
<div id="collapse1" th:if="${#messages.msgOrNull('payment.' + payment.id + '.additionalInfo') != null}" th:utext="#{|payment.${payment.id}.additionalInfo|}" [...]>
Hello, world!
</div>

Answer 2

You can use th:if to add the element only if it isn't null and isn't equal to a empty string (I don't know how you implemented the object).
<div id="collapse1"
th:if="${payment.${payment.id}.additionalInfo != null && payment.${payment.id}.additionalInfo != ''}"
th:utext="#{|payment.${payment.id}.additionalInfo|}" [...]
>
Hello, world!
</div>
... and you should also change the id property. In your impelementation there could be more than one element with id "collapse1".
If you also don't want to show the input field use a th:block element and place the th:if attribute there:
<div th:each="payment : ${paymentList}">
<th:block
th:if="${ ... && ... }"
>
<input ...>
<div ...>
</div>
</th:block>
</div>