/**     * 通用的查询方法：SELECT     */    @SuppressWarnings({ "unchecked", "rawtypes" })    public List testResultSet(String sql) {        Connection connection = null;        Statement statement = null;        ResultSet rs = null;        try {            // 1.获取Connection            connection = JDBCTools.getConnection();            // 2.获取Statement            statement = connection.createStatement();            // 4.执行查询，得到ResultSet            rs = statement.executeQuery(sql);            // 5.处理ResultSet            List list = new ArrayList();            ResultSetMetaData metaData = rs.getMetaData();            int columnCount = metaData.getColumnCount();            while (rs.next()) {                Map rowData = new HashMap();                for (int i = 1; i < columnCount; i++) {                    rowData.put(metaData.getColumnName(i), rs.getObject(i));                }                list.add(rowData);            }            for (int i = 0;i < list.size();i++) {                System.out.print(list.get(i));                System.out.println();            }            return list;        } catch (Exception e) {            e.printStackTrace();            return null;        } finally {            // 6.关闭数据库相应的资源            JDBCTools.release(rs, statement, connection);        }    }