第一步 导入包：<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
第二步：${fn:substring(str,0,10)} 

<select id="dataSourceId" name="dataSourceId">
<c:forEach items="${dataSourceConfigList}" var="dataSource">
    <c:choose>
        <c:when test="${dataSource.id eq datasource_id}">
            <option value="${dataSource.id}" selected="true">${dataSource.name}</option>
        </c:when>
        <c:otherwise>
            <option value="${dataSource.id}">${dataSource.name}</option>
        </c:otherwise>
    </c:choose>
</c:forEach>
</select>