我想要把查询到的List给遍历出来返回给前端树状菜单，但是遍历的时候转换类型报错了，逻辑层代码：
List<Map<String, Object>> metadataList = metadataService.getAllMeatadata(send_parentid);
List<Map<String, Object>> treeList = new ArrayList<Map<String, Object>>();
Map<String, Object> treeMap = null;

            //循环遍历
    for (Map<String, Object> rowMap : metadataList) {
        String metadata_id = String.valueOf(rowMap.get("metadata_id"));
        String metadata_name = String.valueOf(rowMap.get("metadata_name")).trim();
        String parent_id = String.valueOf(rowMap.get("parent_id"));
        String isLeaf = String.valueOf(rowMap.get("isleaf"));
        String grade = String.valueOf(rowMap.get("grade"));
        String metadata_type = String.valueOf(rowMap.get("metadata_type"));
        
        //JOptionPane.showMessageDialog(null, isLeaf);
        treeMap = new HashMap<String, Object>();
        treeMap.put("id", metadata_id);
        treeMap.put("pId", parent_id);
        treeMap.put("name", metadata_name);
        treeMap.put("grade", grade);
        treeMap.put("isleaf", isLeaf);
        treeMap.put("metadata_type", metadata_type);
        
        if (isLeaf.equals("0")) {
            treeMap.put("isParent", true);
        }
        
        treeList.add(treeMap);
        
    }

业务层：//查询所有菜单
List<Map<String, Object>> getAllMeatadata(String send_parentid) throws Exception;
报错:java.lang.ClassCastException: com.gysa.manage.bean.MetadataBean cannot be cast to java.util.Map

是不是可以用其他的方式来接收或者有什么解决办法？麻烦各位大佬了！