ThymeLeaf Fragment executed on false th:if

Question

I'm using Thymeleaf packaged with Spring-Boot. Here is the main template:

<div class="container">
    <table th:replace="fragments/resultTable" th:if="${results}">
        <tr>
            <th>Talent</th>
            <th>Score</th>
        </tr>
        <tr>
            <td>Confidence</td>
            <td>1.0</td>
        </tr>
    </table>
</div>

And it uses this fragment:

<table th:fragment="resultTable">
    <tr>
        <th>Talent</th>
        <th>Score</th>
    </tr>
    <tr th:each="talent : ${talents}">
        <td th:text="${talent}">Talent</td>
        <td th:text="${results.getScore(talent)}">1.0</td>
    </tr>
</table>

The fragment only works if there is a results object. That makes sense to me. So based on the syntax from the documentation I added the th:if statement to the main template file. However I'm still getting this error when I access the template without an object

Attempted to call method getScore(com.model.Talent) on null context object

Shouldn't the th:if statement prevent that code from being accessed?

The template still works fine when the results object is populated, but how do I get the null case to render without the table?

Answer 1

Fragment inclusion has a higher operator precedence than th:if.

http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#attribute-precedence

You'll probably have to move the th:if to a tag above. Either in the container div, or if you still need the container div, then a th:block like this:

<div class="container">
    <th:block th:if="${results}">
        <table th:replace="fragments/resultTable">
            <tr>
                <th>Talent</th>
                <th>Score</th>
            </tr>
            <tr>
                <td>Confidence</td>
                <td>1.0</td>
            </tr>
        </table>
    </th:block>
</div>

Answer 2

With Thymeleaf 3.0 you can use the no-operation token to insert/replace only if condition is met, something like this:

<table th:replace="${results} ? ~{fragments :: resultTable} : _">

https://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#advanced-conditional-insertion-of-fragments