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 ) //querystri
    private 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

@Override
    public 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;
    }