Java 树形结构数据如何高效返回给前端进行展示？

在开发过程中我们总是遇到一些具有层次结构的数据，这些数据在前端也总是需要以树形结构进行显示，那么后端接口如何高效的去将这些数据封装成树形结构呢？下面来进行解析讲解。 

• 最终实现的一个结果图

 

• 设计返回的实体VO

import com.fasterxml.jackson.annotation.JsonFormat;
import io.swagger.v3.oas.annotations.media.Schema;
import lombok.Data;
import lombok.EqualsAndHashCode;
import org.springframework.format.annotation.DateTimeFormat;import java.io.Serializable;
import java.time.LocalDateTime;
import java.util.List;import static cn.iocoder.yudao.framework.common.util.date.DateUtils.FORMAT_YEAR_MONTH_DAY_HOUR_MINUTE_SECOND;
import static cn.iocoder.yudao.framework.common.util.date.DateUtils.TIME_ZONE_DEFAULT;@Schema(description = "知识库管理- 知识字典 - Response VO")
@Data
@EqualsAndHashCode(callSuper = false)
public class KnowledgeBaseDictTreeResVO implements Serializable {@Schema(description = "主键id")private Long id;@Schema(description = "父级菜单id")private Long parentId;@Schema(description = "父级菜单名称")private String parentMenuName;@Schema(description = "菜单名称")private String menuName;@Schema(description = "菜单层级:1：一级菜单；2：二级菜单；3：三级菜单；4：四级菜单；")private Integer menuLevel;@Schema(description = "归属系统")private String belongingSystem;@Schema(description = "排序序号")private Integer sort;@Schema(description = "创建时间")@JsonFormat(pattern = FORMAT_YEAR_MONTH_DAY_HOUR_MINUTE_SECOND, timezone = TIME_ZONE_DEFAULT) //jsonstring@DateTimeFormat(pattern =FORMAT_YEAR_MONTH_DAY_HOUR_MINUTE_SECOND ) //querystriprivate LocalDateTime createTime;@Schema(description = "子集")List<KnowledgeBaseDictTreeResVO> children;}

• Controller层代码

@PostMapping("/getKnowledgeBaseDictTreeList")@Operation(summary = "获取知识字典树形列表")@PreAuthorize("@ss.hasPermission('knowledgebase:problem:knowledgeBaseDict:list')")public CommonResult<List<KnowledgeBaseDictTreeResVO>> getKnowledgeBaseDictTreeList(@Valid @RequestBody KnowledgeBaseDictQueryReqVO reqVO) {return CommonResult.success(knowledgeBaseDictService.getKnowledgeBaseDictTreeList(reqVO));}

import io.swagger.v3.oas.annotations.media.Schema;
import lombok.Data;@Schema(description = "知识字典树形列表查询参数 - Request Search VO")
@Data
public class KnowledgeBaseDictQueryReqVO {@Schema(description = "菜单名称")private String menuName;@Schema(description = "归属系统名称")private String belongingSystemName;@Schema(description = "归属系统id")private Long belongingSystemId;}

• Service层代码

@Overridepublic List<KnowledgeBaseDictTreeResVO> getKnowledgeBaseDictTreeList(KnowledgeBaseDictQueryReqVO reqVO) {// 先查询所有顶层级结构List<KnowledgeBaseDictDO> kbddoTopList = knowledgeBaseDictMapper.getKnowledgeBaseDictTopLevel(reqVO);List<KnowledgeBaseDictTreeResVO> kbdtrvList = KnowledgeBaseDictConvert.INSTANCE.convert(kbddoTopList);// 查询所有知识字典数据List<KnowledgeBaseDictDO> allList = knowledgeBaseDictMapper.getKnowledgeBaseDictAllList(reqVO);List<KnowledgeBaseDictTreeResVO> allkbdtrvList = KnowledgeBaseDictConvert.INSTANCE.convert(allList);List<KnowledgeBaseDictTreeResVO> result = new ArrayList<>();for (KnowledgeBaseDictTreeResVO kbddoTop : kbdtrvList) {result.add(getTreeChildren(kbddoTop,allkbdtrvList));}return result;}

核心实现如下： 

/*** 递归获取子级菜单* @param vo 父级菜单* @param list 所有菜单* @return*/private KnowledgeBaseDictTreeResVO getTreeChildren(KnowledgeBaseDictTreeResVO vo,List<KnowledgeBaseDictTreeResVO> list){List<KnowledgeBaseDictTreeResVO> childrenList = new ArrayList<>();for(KnowledgeBaseDictTreeResVO otv : list){if (vo.getId().equals(otv.getParentId())) {childrenList.add(getTreeChildren(otv,list));}}vo.setChildren(childrenList);return vo;}