如何将具有未知列数的ResultSet映射到List并将其显示在HTML表中？ [英] How to map a ResultSet with unknown amount of columns to a List and display it in a HTML table?

问题描述

我使用Netbeans，GlassFish和JavaDB创建了一个数据库应用程序。现在我的控制器Servlet代码执行一些动态SQL查询并返回一个结果集（或者我可以改变toString）。现在，如何以表格格式显示返回的结果集（我不知道结果集的结构）。有人可以帮我吗？

I have created a Database Application using Netbeans, GlassFish and JavaDB. Now my controller Servlet code executes some dynamic SQL queries and get back a Result Set (or I can ahange toString). Now, how can I show the returned Result Set in a tabular format ( I have no idea about structure of result set). Can anybody help me about this ?

推荐答案

你可以用 Map< String，Object> 代表动态行，即可迭代 c为C：的forEach> 。您可以使用 ResultSetMetaData 收集有关列的信息，例如列数和列标签。

You can use Map<String, Object> to represent a "dynamic" row, which is iterable in <c:forEach>. You can use ResultSetMetaData to collect information about the columns such as the column count and the column labels.

所以，这个映射应该这样做：

So, this mapping should do:

List<Map<String, Object>> rows = new ArrayList<Map<String, Object>>();
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();

while (resultSet.next()) {
    Map<String, Object> columns = new LinkedHashMap<String, Object>();

    for (int i = 1; i <= columnCount; i++) {
        columns.put(metaData.getColumnLabel(i), resultSet.getObject(i));
    }

    rows.add(columns);
}

您可以按如下方式在JSP中显示它：

You can display it in JSP as follows:

<table>
  <thead>
    <tr>
      <c:forEach items="${rows[0]}" var="column">
        <td><c:out value="${column.key}" /></td>
      </c:forEach>
    </tr>
  </thead>
  <tbody>
    <c:forEach items="${rows}" var="columns">
      <tr>
        <c:forEach items="${columns}" var="column">
          <td><c:out value="${column.value}" /></td>
        </c:forEach>
      </tr>
    </c:forEach>
  </tbody>
</table>

这篇关于如何将具有未知列数的ResultSet映射到List并将其显示在HTML表中？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！