本文实例为大家分享了java转树形结构工具类的具体代码，供大家参考，具体内容如下
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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 { /** * 将 List 转为树形结构 * * @param origList : 要转换的 List * @param idFieldName : id字段名 * @param parentIdFieldName : parentId 字段名 * @param childrenFieldName : children 字段名 * @param <T> : 拥有父子结构的 Entity * @return : 树形结果 * @throws Exception . */ public static <T> List<T> convert(List<T> origList, String idFieldName, String parentIdFieldName, String childrenFieldName) throws Exception { // 用于保存当前 id 索引的实体类 Map<String, T> idMaps = new HashMap<>(); // 暂存区, 用于保存没有找到父 id 的控件 List<T> tempList = new ArrayList<>(); List<T> result = new ArrayList<>(); for (T entity : origList) { // 获取 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为空的资料"); } idMaps.put(id, entity); if (StringUtils.isEmpty(parentId)) { // 如果父 id 为空, 则实体类为第一层 result.add(entity); } else { // 根据父 id 获取实体类 T parentEntity = idMaps.get(parentId); if (parentEntity == null) { // 没找到先放入暂存区 tempList.add(entity); } else { // 父组件判断是否存在 children, 不存在新增, 存在则直接假如 setChildrenValue(childrenFieldName, entity, parentEntity); } } } // 处理暂存区, 暂存区的一定不为根节点, 所以它只要父节点存在, 那么此轮查询一定能找到父节点(上一轮已经将全部节点放入 idMaps) for (T entity : tempList) { // 获取 parentId String parentId = Objects.toString(getFieldValue(entity, parentIdFieldName), ""); // 根据父id获取实体类 T parentEntity = idMaps.get(parentId); if (parentEntity == null) { throw new Exception("存在孤立的子节点"); } else { // 父组件判断是否存在children, 不存在新增, 存在则直接假如 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("字段名称[%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("字段名称[%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, "一级节点" + i); list.add(demo); } for (int i = 5; i < 15; i++) { Demo demo = new Demo(i, i % 5, "二级节点" + i); list.add(demo); } for (int i = 15; i < 100; i++) { Demo demo = new Demo(i, i % 10 + 5, "三级节点" + i); list.add(demo); } Demo demo = new Demo(100, 102, "非法节点"); 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内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/l707268743/article/details/106642018
