springboot构造树形结构数据并查询的方法是什么

本篇内容主要讲解“SpringBoot构造树形结构数据并查询的方法是什么”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“springboot构造树形结构数据并查询的方法是什么”吧!

因为项目需要，页面上需要树形结构的数据进行展示（类似下图这样），因此需要后端返回相应格式的数据。

我这里用的是springboot+mybatis-plus+mysql，示例的接口是查询一级权限以及二级权限、三级权限整个权限树…

下面是导入的Maven依赖

 <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-WEB</artifactId>        </dependency><!--数据库连接-->        <dependency>            <groupId>com.alibaba</groupId>            <artifactId>druid-spring-boot-starter</artifactId>            <version>1.1.21</version>        </dependency>         <dependency>            <groupId>Mysql</groupId>            <artifactId>mysql-connector-java</artifactId>        </dependency>        <!--mybatis增强工具-->        <dependency>            <groupId>com.baomidou</groupId>            <artifactId>mybatis-plus-boot-starter</artifactId>            <version>3.4.0</version>        </dependency>  <dependency>            <groupId>org.projectlombok</groupId>            <artifactId>lombok</artifactId>            <optional>true</optional>        </dependency>        <dependency>            <groupId>cn.hutool</groupId>            <artifactId>hutool-all</artifactId>            <version>5.0.6</version>        </dependency>

下面是实体类Permission

@Datapublic class Permission implements Serializable {    @TableId    private String permissionId;    @NotNull(message = "权限名称不能为空")    private String permissionName;        @NotNull(message = "权限标识不能为空")    private String permissionCode;        @NotBlank(message = "父菜单ID不能为空")    private String parentId;        private String path;        private Integer sort;        private LocalDateTime createTime;        private LocalDateTime updateTime;        private String delFlag;    public Permission() {        this.permissionId = IdUtil.simpleUUID();    }

树形结点类

@Datapublic class Treenode {    protected String id;    protected String parentId;    protected List<TreeNode> children = new ArrayList<TreeNode>();    protected boolean hasChildren;   public void addTreeNode(TreeNode node){       children.add(node);   }}

树形结点详细信息类

@Data@EqualsAndHashCode(callSuper = true)public class PermissionTree extends TreeNode implements Serializable {    private String permissionName;    private String permissionCode;    private String path;    private Integer sort;    private String label;    private boolean hasChildren;    public PermissionTree() {    }}

构建树形结点工具类（关键），在这里我用@UtilityClass注解就表示这个类中的方法都是静态方法：

@UtilityClasspublic class TreeUtil {    public <T extends TreeNode> List<T> build(List<T> treeNodes, String root) {        List<T> trees = new ArrayList<>();        for (T treeNode : treeNodes) {            if (root.equals(treeNode.getParentId())) {                trees.add(treeNode);            }            for (T node : treeNodes) {                if (node.getParentId().equals(treeNode.getId())) {                    treeNode.addTreeNode(node);                    treeNode.setHasChildren(true);                }            }        }        return trees;    }        public List<PermissionTree> buildTree(List<Permission> permissionList, String root) {        System.out.println(Arrays.toString(permissionList.toArray()));        List<PermissionTree> treeNodeList = new ArrayList<>();        PermissionTree treeNode = null;        for (Permission permission : permissionList) {            treeNode = new PermissionTree();            treeNode.setId(permission.getPermissionId());            treeNode.setPermissionName(permission.getPermissionName());            treeNode.setPath(permission.getPath());            treeNode.setSort(permission.getSort());            treeNode.setParentId(permission.getParentId());            treeNode.setLabel(permission.getPermissionName());            treeNode.setHasChildren(false);            treeNodeList.add(treeNode);        }        return TreeUtil.build(treeNodeList, root);    }  }

响应消息主体类

@ToString@NoArgsConstructor@AllArgsConstructor@Accessors(chain = true)public class R<T> implements Serializable {private static final long serialVersionUID = 1L;private int code;private String msg;private T data;public int getCode() {return code;}public void setCode(int code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public T getData() {return data;}public void setData(T data) {this.data = data;}public static <T> R<T> ok() {return restResult(null, CommonConstants.SUCCESS, CommonConstants.MSG_SUCCESS);}public static <T> R<T> ok(T data) {return restResult(data, CommonConstants.SUCCESS, CommonConstants.MSG_SUCCESS);}public static <T> R<T> ok(T data, String msg) {return restResult(data, CommonConstants.SUCCESS, msg);}public static <T> R<T> failed() {return restResult(null, CommonConstants.FAIL, null);}public static <T> R<T> failed(String msg) {return restResult(null, CommonConstants.FAIL, msg);}public static <T> R<T> failed(T data) {return restResult(data, CommonConstants.FAIL, null);}public static <T> R<T> failed(T data, String msg) {return restResult(data, CommonConstants.FAIL, msg);}private static <T> R<T> restResult(T data, int code, String msg) {R<T> apiResult = new R<>();apiResult.setCode(code);apiResult.setData(data);apiResult.setMsg(msg);return apiResult;}}

数据查询接口mapper类

@Mapperpublic interface PermissionMapper extends BaseMapper<Permission>{    }

数据逻辑处理业务接口

public interface PermissionService extends IService<Permission> {          List<PermissionTree> treePermission(boolean lazy, String parentId);}

数据逻辑处理业务接口实现类

@Servicepublic class PermissionServiceImpl extends ServiceImpl<PermissionMapper, Permission> implements PermissionService {    @Override    public List<PermissionTree> treePermission(boolean lazy, String parentId) {        if (!lazy) {            return TreeUtil.buildTree(                    baseMapper.selectList(Wrappers.<Permission>lambdaQuery().orderByAsc(Permission::getSort)),                    CommonConstants.PERMISSION_ROOT_ID);        }        String parent = parentId == null ? CommonConstants.PERMISSION_ROOT_ID : parentId;        return TreeUtil.buildTree(                baseMapper.selectList(Wrappers.<Permission>lambdaQuery().eq(Permission::getParentId, parent).orderByAsc(Permission::getSort)), parent        );    }}

查询权限树请求接口类

@RestController@RequestMapping("/permission")public class PermissionController {    @Autowire    private PermissionService permissionService;        @RequestMapping(value = "/getTree", method = RequestMethod.GET)    public R getTree(boolean lazy, String parentId) {        return R.ok(permissionService.treePermission(lazy, parentId));    } }

表中测试数据如下（注意它的parent_id）

测试一：不是懒加载，查询整个权限树。 结果如下。

{    "code": 0,    "msg": "SUCCESS",    "data": [        {            "id": "1",            "parentId": "-1",            "children": [                {                    "id": "2",                    "parentId": "1",                    "children": [                        {                            "id": "3",                            "parentId": "2",                            "children": [],                            "hasChildren": false,                            "permissionName": "update",                            "permissionCode": null,                            "path": null,                            "sort": 3,                            "label": "update",                            "owned": false                        },                        {                            "id": "4",                            "parentId": "2",                            "children": [],                            "hasChildren": false,                            "permissionName": "insert_role",                            "permissionCode": null,                            "path": null,                            "sort": 4,                            "label": "insert_role",                            "owned": false                        }                    ],                    "hasChildren": true,                    "permissionName": "delete",                    "permissionCode": null,                    "path": null,                    "sort": 2,                    "label": "delete",                    "owned": false                }            ],            "hasChildren": true,            "permissionName": "add",            "permissionCode": null,            "path": null,            "sort": 1,            "label": "add",            "owned": false        },        {            "id": "5",            "parentId": "-1",            "children": [],            "hasChildren": false,            "permissionName": "role:saveRole",            "permissionCode": null,            "path": "/role/saveRole",            "sort": 5,            "label": "role:saveRole",            "owned": false        }    ]}

测试二：是懒加载，根据parent_id查询当前分支。 结果如下。

{    "code": 0,    "msg": "SUCCESS",    "data": [        {            "id": "3",            "parentId": "2",            "children": [],            "hasChildren": false,            "permissionName": "update",            "permissionCode": null,            "path": null,            "sort": 3,            "label": "update",            "owned": false        },        {            "id": "4",            "parentId": "2",            "children": [],            "hasChildren": false,            "permissionName": "insert_role",            "permissionCode": null,            "path": null,            "sort": 4,            "label": "insert_role",            "owned": false        }    ]}

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