【将一个Tree结构数据复制到另一个表中并保持树结构】

使用栈内存防止大数据栈溢出

 // 保存单个节点到目标表
private TargetEntity saveNode(TreeNode node, Long parentId) {
	TargetEntity entity = new TargetEntity(node, parentId);
    return targetRepository.save(entity); // JPA 保存操作
}
    
public void processTreeIteratively(TreeNode root) {
	Stack<TreeNodeWithParentId> stack = new Stack<>();
	    
	    // 处理根节点
	    TargetEntity savedRoot = saveNode(root, null);
	    if (root.getChildren() != null) {
	        stack.push(new TreeNodeWithParentId(root, savedRoot.getId()));
	    }
	    
	    // 迭代处理所有节点
	    while (!stack.isEmpty()) {
	        TreeNodeWithParentId current = stack.pop();
	        TreeNode node = current.getNode();
	        Long parentId = current.getParentId();
	        
	        // 处理当前节点的子节点
	        for (TreeNode child : node.getChildren()) {
	            TargetEntity savedChild = saveNode(child, parentId);
	            if (child.getChildren() != null) {
	                stack.push(new TreeNodeWithParentId(child, savedChild.getId()));
	            }
	        }
	    }
}

// 辅助类：保存节点及其父节点ID
private static class TreeNodeWithParentId {
    private TreeNode node;
    private Long parentId;
    
    public TreeNodeWithParentId(TreeNode node, Long parentId) {
        this.node = node;
        this.parentId = parentId;
    }
    
    // getters
}