springboot构造树形结构数据并查询的方法
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。
不说废话，直接开干！！！
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
@Data
public class Permission implements Serializable {
@TableId
private String permissionId;
@NotNull(message = "权限名称不能为空")
private String permissionName;
/**
* 权限标识
*/
@NotNull(message = "权限标识不能为空")
private String permissionCode;
/**
* 父菜单ID，如果是-1就表示是一级权限菜单。
*/
@NotBlank(message = "父菜单ID不能为空")
private String parentId;
/**
* 前端URL访问接口路径
*/
private String path;
/**
* 排序值
*/
private Integer sort;
/**
* 创建时间
*/
private LocalDateTime createTime;
/**
* 更新时间
*/
private LocalDateTime updateTime;
/**
* 0--正常 1--删除
*/
private String delFlag;
public Permission() {
this.permissionId = IdUtil.simpleUUID();
}
树形结点类
@Data
public 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：
@UtilityClass
public 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;
}
/**
* 通过permission创建树形节点
*
* @param permissionList
* @param root
* @return
*/
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
/**
* 响应信息主体
*
* @param <T>
*/
@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
@Mapper
public interface PermissionMapper extends BaseMapper<Permission>{
}
数据逻辑处理业务接口
public interface PermissionService extends IService<Permission> {
/**
* 构建权限树
*
* @param lazy
* @param parentId
* @return
*/
List<PermissionTree> treePermission(boolean lazy, String parentId);
}
数据逻辑处理业务接口实现类
@Service
public class PermissionServiceImpl extends ServiceImpl<PermissionMapper, Permission> implements PermissionService {
/**
* 构建权限树：1、不是懒加载情况，查询全部
* 2、是懒加载，根据parentId查询
*
* @param lazy
* @param parentId
* @return
*/
@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;
/**
* 查询权限列表，并以树状结构显示
*
* @param lazy 懒加载: false时, parentId这个参数失效, 加载所有的权限; true时, 根据parentId加载
* @param parentId
* @return
*/
@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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