Java如何使用遞歸查詢多級樹形結(jié)構(gòu)數(shù)據(jù)(多級菜單)

更新時(shí)間：2024年07月17日 09:40:16 作者：小徐敲java

這篇文章主要介紹了Java如何使用遞歸查詢多級樹形結(jié)構(gòu)數(shù)據(jù)(多級菜單),具有很好的參考價(jià)值,希望對大家有所幫助,如有錯(cuò)誤或未考慮完全的地方,望不吝賜教

1：數(shù)據(jù)庫表

字段resource_id為自增主鍵，其中最頂級的菜單的父類ID是用-1表示的

下面我們就來查詢這張表

2：實(shí)體類

childMenu是用于裝子類數(shù)據(jù)的；

@TableField(exist = false)表示該屬性不為數(shù)據(jù)庫表字段，但是必須使用

package org.jeecg.modules.system.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.fasterxml.jackson.annotation.JsonFormat;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;
import org.springframework.format.annotation.DateTimeFormat;
import java.util.Date;
import java.util.List;

@Data
@TableName("sys_depart_Manage")
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel(value="部門對象", description="部門對象")
public class SysDepartManage {
	
	/**部門名稱*/
    @ApiModelProperty(value = "部門名稱")
	private String departName;

	/**資源id*/
	@ApiModelProperty(value = "資源id")
	@TableId(type = IdType.AUTO)
	private Integer resourceId;

	/**父id*/
	@ApiModelProperty(value = "父id")
	private String parentId;

	/**是否展示*/
	@ApiModelProperty(value = "是否展示")
	private Integer showInput;


	/**創(chuàng)建時(shí)間*/
	@JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd HH:mm:ss")
    @DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")
    @ApiModelProperty(value = "創(chuàng)建時(shí)間")
	private Date createTime;

	/**更新時(shí)間*/
	@JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd HH:mm:ss")
    @DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")
    @ApiModelProperty(value = "更新時(shí)間")
	private Date updateTime;

	/** 子類菜單數(shù)據(jù) */
	@TableField(exist = false)
	private List<SysDepartManage> childMenu;

}

3：controller層代碼

	@Resource
    private ISysDepartManageService sysDepartManageService;
	/**
     * 部門樹形查詢
     * @param parentID
     * @return
     */
    @GetMapping("/menu")
    @ApiOperation(value="部門樹形查詢", notes="部門樹形查詢")
    public List<SysDepartManage> findMenu(@RequestParam String parentID) {
        return sysDepartManageService.findMenu(parentID);
    }

4：service層代碼

package org.jeecg.modules.system.service;

import com.baomidou.mybatisplus.extension.service.IService;
import org.jeecg.modules.system.entity.SysDepartManage;
import java.util.List;
import java.util.Map;

public interface ISysDepartManageService extends IService<SysDepartManage> {

    List<SysDepartManage> findMenu(String parentID );

}

5：方法

serviceimpl層代碼（多次查詢數(shù)據(jù)庫，耗性能）

package org.jeecg.modules.system.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.jeecg.modules.system.entity.SysDepartManage;
import org.jeecg.modules.system.mapper.SysDepartManageMapper;
import org.jeecg.modules.system.service.ISysDepartManageService;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Map;

/**
 * @Description: 部門角色
 * @Author: jeecg-boot
 * @Date:   2020-02-12
 * @Version: V1.0
 */
@Service
public class SysDepartManageServiceImpl extends ServiceImpl<SysDepartManageMapper, SysDepartManage> implements ISysDepartManageService {

    @Override
    public List<SysDepartManage> findMenu(String parentID) {
        QueryWrapper queryWrapper = new QueryWrapper<>();
        //查詢條件
        queryWrapper.eq("parent_id", parentID);
        List<SysDepartManage> list = baseMapper.selectList(queryWrapper);
        for (SysDepartManage departManage : list) {
            //遞歸子類數(shù)據(jù)
            departManage.setChildMenu(findMenu(departManage.getResourceId().toString()));
        }
        return list;
    }
}

6：方法2：serviceimpl層代碼（只查詢數(shù)據(jù)庫1次）

package org.jeecg.modules.system.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.jeecg.modules.system.entity.SysDepartManage;
import org.jeecg.modules.system.mapper.SysDepartManageMapper;
import org.jeecg.modules.system.service.ISysDepartManageService;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;


@Service
public class SysDepartManageServiceImpl extends ServiceImpl<SysDepartManageMapper, SysDepartManage> implements ISysDepartManageService {


    @Override
    public List<SysDepartManage> findMenu(String parentID) {
        //數(shù)據(jù)查詢
        List<SysDepartManage> list = baseMapper.selectList(new QueryWrapper());
        //新建一個(gè)用于接收數(shù)據(jù)的list
        List<SysDepartManage> resultList = new ArrayList<>();
        for (SysDepartManage result : list) {
            if (result.getParentId() == 0) {
                //調(diào)用方法給子類添加數(shù)據(jù)
                resultList.add(getMenuTree(result, list));
            }
        }
        return resultList;
    }

    private SysDepartManage getMenuTree(SysDepartManage result, List<SysDepartManage> list) {
        for (SysDepartManage sysDepartManage : list) {
            //如果父類主鍵等于傳過來實(shí)體類的ID
            if (sysDepartManage.getParentId().equals(result.getResourceId())) {
                if (result.getChildMenu() == null) {
                    result.setChildMenu(new ArrayList<>());
                }
                // 遞歸調(diào)用
                result.getChildMenu().add(getMenuTree(sysDepartManage, list));
            }
        }
        return result;
    }

}

7：mapper層代碼

package org.jeecg.modules.system.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.jeecg.modules.system.entity.SysDepartManage;
import java.util.List;
import java.util.Map;


public interface SysDepartManageMapper extends BaseMapper<SysDepartManage> {
    
}