树表转换成有层次的List列表（无限层级）

我的项目环境：mybaits plus

我负责的模块：course_category（课程分类模块）

方法一，传统的遍历组装

这一个方法有问题，先别用

方法二，Hutool自带TreeUtil

    @GetMapping("/tree2")public List tree() {// 1.取出所有的课程分类List<CourseCategory> list = categoryService.list();// 2. Hutool 配置TreeNodeConfig treeNodeConfig = new TreeNodeConfig();// 3.设置一下这个最大深度，建议必须设置treeNodeConfig.setDeep(2);// 3. 直接生成树（根节点 parentId = "0"）List<Tree<String>> tree = TreeUtil.build(list,"0",treeNodeConfig,(category, treeNode) -> {// 一定要setId和setParentId才会出现树treeNode.setId(category.getId());treeNode.setParentId(category.getParentId());treeNode.setName(category.getCategoryName());//下面是用allgetset插件一键取出这个类的所有String categoryCode = category.getCategoryCode();Integer level = category.getLevel();String parentId = category.getParentId();LocalDateTime createTime = category.getCreateTime();String createBy = category.getCreateBy();Integer courseCount = category.getCourseCount();Integer subCategoryCount = category.getSubCategoryCount();Integer totalCourseCount = category.getTotalCourseCount();List<CourseCategory> children = category.getChildren();// 把上面取出来的值都putExtra进去,除了children。children他会自动组装// children不能添加，肯定会出现问题treeNode.putExtra("categoryCode", categoryCode);treeNode.putExtra("level", level);treeNode.putExtra("parentId", parentId);treeNode.putExtra("createTime", createTime);treeNode.putExtra("createBy", createBy);treeNode.putExtra("courseCount", courseCount);treeNode.putExtra("subCategoryCount", subCategoryCount);treeNode.putExtra("totalCourseCount", totalCourseCount);});return tree;}

返回结果：（id，parentId，name是set进去的，children是自动组装的，其他的字段要通过putExtra）

[{"id": "18bfc4df4e7b462eaf125b5999a20edf","parentId": "0","name": "组织协同","categoryCode": "10000258","level": 1,"createTime": "2025-08-19T13:39:05","createBy": "cs_huiren","courseCount": 0,"subCategoryCount": 1,"totalCourseCount": 1,"children": [{"id": "2f46ba4e2cec46eaab1a9a6c313bc503","parentId": "18bfc4df4e7b462eaf125b5999a20edf","name": "领导力培养","categoryCode": "21AD45AF","level": 2,"createTime": "2025-08-19T13:39:22","createBy": "cs_huiren","courseCount": 1,"subCategoryCount": 0,"totalCourseCount": 1,"children": null}]},{"id": "812b471578f34044a9ccf5da00022e61","parentId": "0","name": "项目管理 ","categoryCode": "10007462","level": 1,"createTime": "2025-08-13T08:26:04","createBy": "cs_huiren","courseCount": 2,"subCategoryCount": 5,"totalCourseCount": 7,"children": [{"id": "3e9c662f66d64744aabea94ba9002dfa","parentId": "812b471578f34044a9ccf5da00022e61","name": "职能支撑 ","categoryCode": "280EE3C3","level": 2,"createTime": "2025-08-13T09:06:05","createBy": "cs_huiren","courseCount": 4,"subCategoryCount": 4,"totalCourseCount": 5,"children": null}]},{"id": "98c858bfa9114c18bc2c60db6e40c8c0","parentId": "0","name": "技术文档","categoryCode": "10001069","level": 1,"createTime": "2025-08-13T09:31:52","createBy": "cs_huiren","courseCount": 2,"subCategoryCount": 0,"totalCourseCount": 2}
]

方法三，mybatisplus自带

MyBatis-Plus 从 3.5.3 开始 已经在  mybatis-plus-extension  中自带了 无限层级树 的工具方法，不用自己写任何递归。

@Data
@TableName("category")
public class Category {private String id;          // 主键private String parentId;    // 父节点private String categoryName;// 子节点，名字固定叫 children@TableField(exist = false)private List<Category> children = new ArrayList<>();
}

@RestController
@RequiredArgsConstructor
public class CategoryController {private final CategoryMapper categoryMapper;@GetMapping("/tree")public List<Category> tree() {return TreeHelper.build(categoryMapper.selectList(null),Category::getId,Category::getParentId,Category::getChildren);}
}