关于java:java之树结构得实现

实体类：

package com.gsl.node.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 lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

/**

@Author ：Guo Shi Lin
@date ： 2020/8/18 13:57
@description：菜单树
@modified By：
@version: 1.0

*/
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tree")
public class Tree {

@TableId(value = "id", type = IdType.AUTO)private Integer id;private String name;private Integer parentId;@TableField(exist = false)private List<Tree> children;

}
数据拜访层接口dao：

package com.gsl.node.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.gsl.node.entity.Tree;
import org.apache.ibatis.annotations.Mapper;

/**

@Author ：Guo Shi Lin
@date ： 2020/8/18 13:58
@description：
@modified By：
@version: 1.0

*/
@Mapper
public interface TreeDao extends BaseMapper<Tree> {

}

业务逻辑层接口service：

package com.gsl.node.service;

import com.gsl.node.entity.Tree;

import java.util.List;

/**

@Author ：Guo Shi Lin
@date ： 2020/8/18 13:58
@description：
@modified By：
@version: 1.0

*/
public interface TreeService {

/** * 查找树 * @return */List<Tree> findList();

}
业务逻辑层实现类impl：
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package com.gsl.node.service.impl;

import com.gsl.node.dao.TreeDao;
import com.gsl.node.entity.Tree;
import com.gsl.node.service.TreeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

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

/**

@Author ：Guo Shi Lin
@date ： 2020/8/18 14:00
@description：用的递归实现
@modified By：
@version: 1.0

*/
@Service
public class TreeServiceImpl implements TreeService {

@Autowiredprivate TreeDao treeDao;@Overridepublic List<Tree> findList() {    return treeDao.selectList(null);}public List<Tree> handleTree() {    //根节点list    List<Tree> treeList = new ArrayList<>();    //从数据库获取所有得数据    List<Tree> allTree = treeDao.selectList(null);    if (null != allTree && allTree.size() > 0) {        allTree.forEach(tree -> {            if (tree.getParentId() == 0) {                treeList.add(tree);            }        });        if (null != treeList && treeList.size() > 0) {            treeList.forEach(tree -> {                //应用递归获取孩子                List<Tree> childrenList = getChildren(tree.getId(), allTree);                tree.setChildren(childrenList);            });        }    }    return treeList;}/** * 应用递归获取根节点上面得孩子 * @param id * @param allTree * @return */public List<Tree> getChildren(Integer id, List<Tree> allTree) {    List<Tree> childrenList = new ArrayList<>();    allTree.forEach(tree -> {        if (tree.getParentId().equals(id)) {            childrenList.add(tree);        }    });    if (null != childrenList && childrenList.size() > 0) {        childrenList.forEach(tree -> {            tree.setChildren(getChildren(tree.getId(), allTree));        });    } else {        return null;    }    return childrenList;}

}
管制层controller：

package com.gsl.node.controller;

import com.gsl.node.entity.Tree;
import com.gsl.node.service.TreeService;
import com.gsl.node.service.impl.TreeServiceImpl;
import com.gsl.result.ResponseResult;
import io.swagger.annotations.Api;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**

@Author ：Guo Shi Lin
@date ： 2020/8/19 9:37
@description：
@modified By：
@version: 1.0

*/
@RestController
@Api(tags = "树")
public class TreeController {

@Autowiredprivate TreeServiceImpl treeService;@GetMapping("tree")public ResponseResult<Tree> tree() {    return new ResponseResult(200, "胜利", treeService.handleTree());}

}
3.测试后果
{

"code": 200,"msg": "胜利","data": [    {        "id": 1,        "name": "根节点",        "parentId": 0,        "children": [            {                "id": 2,                "name": "父节点",                "parentId": 1,                "children": [                    {                        "id": 3,                        "name": "子节点",                        "parentId": 2,                        "children": null                    },                    {                        "id": 4,                        "name": "子节点-1",                        "parentId": 2,                        "children": null                    }                ]            },            {                "id": 5,                "name": "父节点-1",                "parentId": 1,                "children": null            }        ]    },    {        "id": 6,        "name": "根节点-1",        "parentId": 0,        "children": null    }]

}