<div class="card-text">
<div class="form-group" th:each="row : ${card.value.entrySet()}">
<input type="checkbox" id="x" class="form-control" th:field="*{cards[__${card.key}__][__${row.key}__]}" />
<div class="card-text">
<div class="form-group" th:each="row : ${card.value.entrySet()}">
<input type="checkbox" id="x" class="form-control" th:field="*{cards[__${card.key}__][__${row.key}__]}" />