When spring boot uses thymeleaf, does the introduced bootstrap quote one copy of each template, or how to deal with it?

when spring boot uses thymeleaf, does the introduced bootstrap quote one copy of each template, or how to deal with it?

Nov.22,2021

make a public file _ include.html that says

<div th:fragment="header">
    ...
</div>

attract people on the page

<th:block th:include="_include :: header"></th:block>
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