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：

java">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<Map<String, Object>>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

java">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;
    }