樹列表查詢JAVA+MYSQL

項目中用到的服務器返回給前端樹列表代碼實現

使用sql將根節點下所有子節點都查詢出來返回給Java端，只根據parentId查詢，沒有Level等級的需求

select node_id,parent_id,ischild from 
(
	select 
	t1.node_id,
	parent_id,
    if(find_in_set(parent_id, @pids) > 0, @pids := concat(@pids,',',node_id), 'not found') as ischild
				from (select t.node_id,t.parent_id from t_rbac_node t order by parent_id, node_id) t1, 
    (select @pids := 10 id) t2							
)t3 
where ischild != 'not found'
union all 
#連上根節點自己
select node_id,parent_id,null from t_rbac_node where node_id=10

java代碼使用遞歸的方法將數據庫返回的數據組裝成tree

@Override
    public NodeTreeVO getNodeTree(Integer parentId,int[] level) throws Exception {
        Map<String,Object> paramMap=new HashMap<String,Object>();
        paramMap.put("parentId",parentId);
        paramMap.put("level",level);
        List<NodeTreeVO> nodeRoleRespVOS = nodeDOMapper.selectNodeTree(paramMap);
        return getNodeTree(nodeRoleRespVOS,parentId);
    }


    /**
     * @Description 組裝結果
     * @author xpWang
     * @date 2020/1/15 16:52
     */
    private NodeTreeVO getNodeTree(List<NodeTreeVO> dblist,Integer parentId){
        List<NodeTreeVO> result=new ArrayList<NodeTreeVO>();
        NodeTreeVO root=null;
        //獲取根節點
        int index=0;
        for(;index<dblist.size();index++){
            if (parentId==dblist.get(index).getNodeId()){
                root=dblist.get(index);
                break;
            }
        }
        if (root==null){
            return null;
        }
        dblist.remove(index);
        result.add(root);
        getNodeTree(result,dblist);
        return root;
    }

    /**
     * @Description 將dblist裏面的數據插入到resultlist下，遞歸調用
     * @author xpWang
     * @date 2020/1/15 16:53
     */
    public List<NodeTreeVO> getNodeTree(List<NodeTreeVO> result,List<NodeTreeVO> dblist){
        for(NodeTreeVO node:result){
            for (int i=0;i<dblist.size();i++){
                NodeTreeVO nodeTreeVO=dblist.get(i);
                if (dblist.get(i).getParentId()==node.getNodeId()){
                    node.addNode(dblist.get(i));
                    dblist.remove(i);
                    i--;
                }
            }
            getNodeTree(node.getChildren(),dblist);
        }
        return result;
    }

返回給前端的DTO

@Data
public class NodeTreeVO extends NodeDO {
    private List<NodeTreeVO> children=new ArrayList<NodeTreeVO>();
    public void addNode(NodeTreeVO node){
        children.add(node);
    }
}