将数据库查询结果集(ResultSet)映射为HashMap对象

该方法表示了如何将一个数据库查询结果集映射为一个HashMap对象,如:

    public HashMap> getHashMap(ResultSet resultSet) throws SQLException {
        HashMap> objectObjectHashMap = new HashMap<>();
        ArrayList list = new ArrayList<>();
        ResultSetmetaData metaData = resultSet.getmetaData();
        int columnCount = metaData.getColumnCount();//获取结果集有多少个字段
        for (int i = 1; i <= columnCount; i++) {
            //获取字段第几个字段的名称,数据库字段是从1开始的
            String columnLabel = metaData.getColumnLabel(i);
            list.add(columnLabel);
        }
        int Counter = 0;
        for (String s : list) {
            HashMap objectObjectHashMap1 = new HashMap<>();
            while (resultSet.next()) {
                Object object = resultSet.getObject(s);
                objectObjectHashMap1.put(Counter, object);
                Counter++;
            }
            resultSet.beforeFirst();
            objectObjectHashMap.put(s, objectObjectHashMap1);
        }
        return objectObjectHashMap;
    }

好处

大大减少的代码量返回一个HashMap通过遍历可随时获取结果集里的值

如:直接遍历一个id值:

 public static void main(String[] args) throws SQLException {
     HashMap> hashMap=newUserDaoImpl().getHashMap(resultSet);
     HashMap id = hashMap.get("id");
     for (Map.Entry integerObjectEntry : id.entrySet()) {
            System.out.println(integerObjectEntry.getValue());
     }
}