本文實例為大家分享了java轉樹形結構工具類的具體代碼，供大家參考，具體內容如下
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
import com.alibaba.fastjson.JSON;import lombok.Data;import lombok.ToString;import org.springframework.util.ReflectionUtils;import org.springframework.util.StringUtils;import java.lang.reflect.Field;import java.util.*;/** * @author : liyk * @version 1.0 * @date : 2020/6/9 */public class TreeUtil { /** * 將 List 轉為樹形結構 * * @param origList : 要轉換的 List * @param idFieldName : id字段名 * @param parentIdFieldName : parentId 字段名 * @param childrenFieldName : children 字段名 * @param <T> : 擁有父子結構的 Entity * @return : 樹形結果 * @throws Exception . */ public static <T> List<T> convert(List<T> origList, String idFieldName, String parentIdFieldName, String childrenFieldName) throws Exception { // 用于保存當前 id 索引的實體類 Map<String, T> idMaps = new HashMap<>(); // 暫存區(qū), 用于保存沒有找到父 id 的控件 List<T> tempList = new ArrayList<>(); List<T> result = new ArrayList<>(); for (T entity : origList) { // 獲取 id, parentId, children String id = Objects.toString(getFieldValue(entity, idFieldName), ""); String parentId = Objects.toString(getFieldValue(entity, parentIdFieldName), ""); if (StringUtils.isEmpty(id)) { throw new Exception("存在id為空的資料"); } idMaps.put(id, entity); if (StringUtils.isEmpty(parentId)) { // 如果父 id 為空, 則實體類為第一層 result.add(entity); } else { // 根據父 id 獲取實體類 T parentEntity = idMaps.get(parentId); if (parentEntity == null) { // 沒找到先放入暫存區(qū) tempList.add(entity); } else { // 父組件判斷是否存在 children, 不存在新增, 存在則直接假如 setChildrenValue(childrenFieldName, entity, parentEntity); } } } // 處理暫存區(qū), 暫存區(qū)的一定不為根節(jié)點, 所以它只要父節(jié)點存在, 那么此輪查詢一定能找到父節(jié)點(上一輪已經將全部節(jié)點放入 idMaps) for (T entity : tempList) { // 獲取 parentId String parentId = Objects.toString(getFieldValue(entity, parentIdFieldName), ""); // 根據父id獲取實體類 T parentEntity = idMaps.get(parentId); if (parentEntity == null) { throw new Exception("存在孤立的子節(jié)點"); } else { // 父組件判斷是否存在children, 不存在新增, 存在則直接假如 setChildrenValue(childrenFieldName, entity, parentEntity); } } return result; } private static <T> void setChildrenValue(String childrenFieldName, T entity, T parentEntity) throws Exception { Object children = getFieldValue(parentEntity, childrenFieldName); List<T> childrenList; if (children == null) { childrenList = new ArrayList<>(); childrenList.add(entity); setFieldValue(parentEntity, childrenFieldName, childrenList); } else { List<T> childrenReal = (List<T>) children; childrenReal.add(entity); } } private static <T> Object getFieldValue(T entity, String fieldName) throws Exception { Field field = ReflectionUtils.findField(entity.getClass(), fieldName); if (field == null) { throw new Exception(String.format("字段名稱[%s]不存在", fieldName)); } boolean accessible = field.isAccessible(); field.setAccessible(true); Object result = ReflectionUtils.getField(field, entity); field.setAccessible(accessible); return result; } private static <T> void setFieldValue(T entity, String fieldName, Object value) throws Exception { Field field = ReflectionUtils.findField(entity.getClass(), fieldName); if (field == null) { throw new Exception(String.format("字段名稱[%s]不存在", fieldName)); } boolean accessible = field.isAccessible(); field.setAccessible(true); ReflectionUtils.setField(field, entity, value); field.setAccessible(accessible); } public static void main(String[] args) throws Exception { List<Demo> list = new ArrayList<>(); for (int i = 0; i < 5; i++) { Demo demo = new Demo(i, "一級節(jié)點" + i); list.add(demo); } for (int i = 5; i < 15; i++) { Demo demo = new Demo(i, i % 5, "二級節(jié)點" + i); list.add(demo); } for (int i = 15; i < 100; i++) { Demo demo = new Demo(i, i % 10 + 5, "三級節(jié)點" + i); list.add(demo); } Demo demo = new Demo(100, 102, "非法節(jié)點"); list.add(demo); List<Demo> convert = TreeUtil.convert(list, "id", "pid", "children"); String s = JSON.toJSONString(convert); System.out.println(s); }}@Data@ToStringclass Demo { private Integer id; private Integer pid; private String name; private List<Demo> children; public Demo(Integer id, Integer pid, String name) { this.id = id; this.pid = pid; this.name = name; } public Demo(Integer id, String name) { this.id = id; this.name = name; }} |
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
原文鏈接：https://blog.csdn.net/l707268743/article/details/106642018
