部门结构树优化（json递归）

实体类

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public class SysDept {     private static final long serialVersionUID = 1L;       /** 部门ID */     private Long deptId;       /** 父部门ID */     private Long parentId;                /** 子部门 */     private List<SysDept> children = new ArrayList<SysDept>(); }

　　普通list转换为treeList

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public <T> List<T> listToTreeList ( JSONArray arr , String deptId , String parentId , String children,            Class<T> clazz )    {        JSONArray r = new JSONArray();        JSONObject hash = new JSONObject();        //将数组转为Object的形式，key为数组中的deptId        for ( int i = 0;i < arr.size();i++ ) {            JSONObject json = (JSONObject)arr.get(i);            hash.put(json.getString(deptId) , json);        }        //遍历结果集        for ( int j = 0;j < arr.size();j++ ) {            //单条记录            JSONObject aVal = (JSONObject)arr.get(j);            //在hash中取出key为单条记录中parentId的值            JSONObject hashVP = (JSONObject)hash.get(aVal.get(parentId).toString());            //如果记录的parentId存在，则说明它有父节点，将她添加到孩子节点的集合中            if ( hashVP != null ) {                //检查是否有children属性                if ( hashVP.get(children) != null ) {                    JSONArray ch = (JSONArray)hashVP.get(children);                    ch.add(aVal);                    hashVP.put(children , ch);                }                else {                    JSONArray ch = new JSONArray();                    ch.add(aVal);                    hashVP.put(children , ch);                }            }            else {                r.add(aVal);            }        }        return r.toJavaList(clazz);    }

s   数据库中数据结构

 

 

 

方法调用

depts 为List < SysDept > depts 数据库取出的depts

List < SysDept > list = listToTreeList(JSONArray.parseArray(JSON.toJSONString(depts)) , "deptId" , "parentId",
        "children",SysDept.class);

参考连接：https://www.zhihu.com/tardis/sogou/art/68094736