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
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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, 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 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, 暫存區的一定不為根節點, 所以它只要父節點存在, 那么此輪查詢一定能找到父節點(上一輪已經將全部節點放入 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, "一級節點" + i); list.add(demo); } for (int i = 5; i < 15; i++) { Demo demo = new Demo(i, i % 5, "二級節點" + i); list.add(demo); } for (int i = 15; i < 100; i++) { Demo demo = new Demo(i, i % 10 + 5, "三級節點" + i); list.add(demo); } Demo demo = new Demo(100, 102, "非法節點"); 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
