原始資料如下
[
{
"name":"甘肅省",
"pid":0,
"id":1
},
{
"name":"天水市",
"pid":1,
"id":2
},
{
"name":"秦州區",
"pid":2,
"id":3
},
{
"name":"北京市",
"pid":0,
"id":4
},
{
"name":"昌平區",
"pid":4,
"id":5
}
]
現需要是使用java将以上資料轉為樹形結構,轉化後下的結構如下
[
{
"children":[
{
"children":[
{
"name":"秦州區",
"pid":2,
"id":3
}
],
"name":"天水市",
"pid":1,
"id":2
}
],
"name":"甘肅省",
"pid":0,
"id":1
},
{
"children":[
{
"name":"昌平區",
"pid":4,
"id":5
}
],
"name":"北京市",
"pid":0,
"id":4
}
]
代碼如下
/**
* listToTree
* <p>方法說明<p>
* 将JSONArray數組轉為樹狀結構
* @param arr 需要轉化的資料
* @param id 資料唯一的辨別鍵值
* @param pid 父id唯一辨別鍵值
* @param child 子節點鍵值
* @return JSONArray
*/
public static JSONArray listToTree(JSONArray arr,String id,String pid,String child){
JSONArray r = new JSONArray();
JSONObject hash = new JSONObject();
//将數組轉為Object的形式,key為數組中的id
for(int i=0;i<arr.size();i++){
JSONObject json = (JSONObject) arr.get(i);
hash.put(json.getString(id), json);
}
//周遊結果集
for(int j=0;j<arr.size();j++){
//單條記錄
JSONObject aVal = (JSONObject) arr.get(j);
//在hash中取出key為單條記錄中pid的值
JSONObject hashVP = (JSONObject) hash.get(aVal.get(pid).toString());
//如果記錄的pid存在,則說明它有父節點,将她添加到孩子節點的集合中
if(hashVP!=null){
//檢查是否有child屬性
if(hashVP.get(child)!=null){
JSONArray ch = (JSONArray) hashVP.get(child);
ch.add(aVal);
hashVP.put(child, ch);
}else{
JSONArray ch = new JSONArray();
ch.add(aVal);
hashVP.put(child, ch);
}
}else{
r.add(aVal);
}
}
return r;
}
測試代碼如下
public static void main(String[] args){
List<Map<String,Object>> data = new ArrayList<>();
Map<String,Object> map = new HashMap<>();
map.put("id",1);
map.put("pid",0);
map.put("name","甘肅省");
data.add(map);
Map<String,Object> map2 = new HashMap<>();
map2.put("id",2);
map2.put("pid",1);
map2.put("name","天水市");
data.add(map2);
Map<String,Object> map3 = new HashMap<>();
map3.put("id",3);
map3.put("pid",2);
map3.put("name","秦州區");
data.add(map3);
Map<String,Object> map4 = new HashMap<>();
map4.put("id",4);
map4.put("pid",0);
map4.put("name","北京市");
data.add(map4);
Map<String,Object> map5 = new HashMap<>();
map5.put("id",5);
map5.put("pid",4);
map5.put("name","昌平區");
data.add(map5);
System.out.println(JSON.toJSONString(data));
JSONArray result = listToTree(JSONArray.parseArray(JSON.toJSONString(data)),"id","pid","children");
System.out.println(JSON.toJSONString(result));
}