有关自连接表的统一封装

表结构

RecursionBean

@Getter
@Setter
@ToString
@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class RecursionBean<T>  extends BaseVO {/*** 编号*/private T id;/*** 父权限ID，根节点的父权限为空* 注释掉@JsonIgnore，是为了前端判断是否是顶级节点，顶级节点才能添加子节点*/
//    @JsonIgnoreprivate T pid;private List<? extends RecursionBean<T>> children;}

封装从服务器端返回的树形数据：RecursionItem

@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class RecursionItem<T> extends RecursionBean<T> {/*** 名称*/private String name;public RecursionItem(T id, String name) {super.setId(id);this.name = name;}public RecursionItem(T id, String name, List<? extends RecursionBean<T>> children) {super.setId(id);this.name = name;super.setChildren(children);}
}

工具类

public class RecursionBeanUtil {/*** 递归查询子节点** @param root 根节点* @param list 所有节点* @return 根节点信息*/private static <E, T extends RecursionBean<E>> List<T> getChildren(T root, List<T> list) {final List<T> res = new ArrayList<>();for (T item : list) {if (Objects.equals(item.getPid(), root.getId())) {item.setChildren(getChildren(item, list));res.add(item);}}return res;}public static <E, T extends RecursionBean<E>> List<T> getRecursionList(List<T> list) {if (CollectionUtil.isEmpty(list)) {return list;}// 所有的节点final List<E> allList = list.stream().map(T::getId).toList();// 顶级节点（父ID为空）final List<E> topList = list.stream().filter(item -> item.getPid() == null).map(T::getId).toList();// 父级节点（不包含在已有父级列表中的新PID）final List<E> parentList = list.stream().map(T::getPid).filter(itemPid -> !topList.contains(itemPid)).distinct().toList();// 叶子节点（非顶级且不在父级列表中的节点ID）final List<E> leafList = allList.stream().filter(id -> !topList.contains(id)).filter(id -> !parentList.contains(id)).toList();final List<T> res = new ArrayList<>();boolean topFlag = true;// 如果待处理集合中顶级节点for (T item : list) {if (item.getPid() == null) {topFlag = false;item.setChildren(getChildren(item, list));res.add(item);}}if (!topFlag) {return res;}boolean parentFlag = true;//如果待处理集合中没有顶级节点但有父节点for (T item : list) {// 是父节点但不是叶子节点if (parentList.contains(item.getPid()) && !leafList.contains(item.getId())) {item.setChildren(getChildren(item, list));parentFlag = false;res.add(item);}}if (!parentFlag) {return res;}//如果待处理集合中全部是叶子节点for (T item : list) {// 是父节点但不是叶子节点if (leafList.contains(item.getId())) {item.setChildren(getChildren(item, list));res.add(item);}}return res;}
}