resultset判断是否是索引,format命令使用

ResultSet元数据可以使用ResultSet分析结果集中的元素。

ResultSetMetaData meta = rs.getMetaData();

public static void main(String单薄的戒指 args) throws SQLException {

       List<Map<String, Object>> datas = read("select id, name as n from user where id < 5");

    }

static List<Map<String, Object>> read(String sql) throws SQLException {

       Connection conn = null;

       PreparedStatement ps = null;

       ResultSet rs = null;

       try {

           conn = JdbcUtils.getConnection();

           ps = conn.prepareStatement(sql);

           rs = ps.executeQuery();

           ResultSetMetaData rsmd = rs.getMetaData();

           int count = rsmd.getColumnCount();//列的数目

           String单薄的戒指 colNames = new String[count];

           for (int i = 1; i <= count; i++) {

              // System.out.print(rsmd.getColumnClassName(i) + "t");

              // System.out.print(rsmd.getColumnName(i) + "t");

              // System.out.println(rsmd.getColumnLabel(i));

              colNames[i - 1] = rsmd.getColumnLabel(i);//将列的名称放到一个数组当中去。

           }

           List<Map<String, Object>> datas = new ArrayList<Map<String, Object>>();

           while (rs.next()) {

              //每一行

              Map<String, Object> data = new HashMap<String, Object>();

              //data中的Key为列的名称，Value是些列的值

              for (int i = 0; i < colNames.length; i++) {

                  data.put(colNames[i], rs.getObject(colNames[i]));

              //将列的名称与列的值放到map当中去，每一行map中的元素大小就是列的数目

              }

              datas.add(data);//将此行放到List当中去。         }

           return datas;

       } finally {

           JdbcUtils.free(rs, ps, conn);

       }

    }

}