How to convert Thymeleaf data types?

when traversing an array using Thymelaf loops in hmlt

<div th:each="c : ${blog.categories}">
    <span  class="label label-primary" th:text="${c}"></span>
</div>

the display on the page is as follows

clipboard.png

because here ${blog.categories} is a string rather than an array object! In JS, JSON.parse () is fine, but how to solve this problem?

Mar.23,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b361e9-2b83e.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b361e9-2b83e.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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