应用场景
查询某张表，对于返回的执行结果，咱们并不需要知道他有哪些字段，字段名叫啥，直接通过原生JDBC动态的获取列名以及对应的数据。
其实就有点像遍历map集合，并不需要知道key叫啥，一样可以遍历出来：
Map<String,Object> map = Maps.newHashMap(); for (Map.Entry<String, Object> entry : map.entrySet()) { System.out.println(entry.getKey() + " : " + entry.getValue()); }
目标
将数据库查询出来的结果，存放到一个List>集合中，方便后续批量将该集合的数据插入到其他地方
整干货
private List<Map<String, Object>> executeQuery(String sqlStr,String url,String username,String password) { Connection connection = DriverManager.getConnection(url, username, password); Statement statement = null; ResultSet resultSet = null; List<Map<String, Object>> resultList = new ArrayList<Map<String, Object>>(); try { statement = connection.createStatement(); resultSet = statement.executeQuery(sqlStr); final ResultSetMetaData rsmd = resultSet.getMetaData(); final String[] columnName = new String[rsmd.getColumnCount()]; for (int i = 1; i <= rsmd.getColumnCount(); ++i) { columnName[i - 1] = rsmd.getColumnLabel(i); } while (resultSet.next()) { LinkedHashMap<String, Object> map = new LinkedHashMap<String, Object>(); for (int j = 1; j <= rsmd.getColumnCount(); ++j) { if (resultSet.getObject(j) != null && !resultSet.getObject(j).equals("")) { String columnData = resultSet.getObject(j).toString().trim(); map.put(columnName[j - 1], columnData); } else { map.put(columnName[j - 1], ""); } } resultList.add(map); } } catch (SQLException e) { logger.error("SQL语句执行失败",e); }finally { if( null != resultSet ) { resultSet.close(); } if( null != statement ) { statement.close(); } if( null != connection ) { connection .close(); } } return resultList; }
