<%@ page contentType="text/html; charset=utf-8" %>
    ...
    <div class="container">

➊

        <div class="float-right">
        <form:form action="${pageContext.request.contextPath}/logout" method="POST">
           <input type="submit" class="btn btn-success" value="Logout"/>
        </form:form>
        </div>

    <div class="float-right" style="padding-right:30px">
        <a href="?language=ko">Korean</a>|<a href="?language=en">English</a>
    </div>
<br>
<br>

    <form:form modelAttribute="NewBook"
               action="./add?${_csrf.parameterName}=${_csrf.token}" 
               class="form-horizontal" enctype="multipart/form-data">
    <fieldset>
...