Java 无限级递归树形菜单

1. 首先获取所有节点的父节点。
2. 递归创建父节点下的子节点树，并拼接。
3. 递归子节点建立次子节点并拼接上，直至末端。

建立数据模型SysDept

public class SysDept {
    /**
     * Column: dept_id
     * Type: BIGINT
     * Remark: 部门id
     */
    private Long deptId;

    /**
     * Column: parent_id
     * Type: BIGINT
     * Default value: 0
     * Remark: 父部门id
     */
    private Long parentId;

    /**
     * Column: dept_name
     * Type: VARCHAR(30)
     * Remark: 部门名称
     */
    private String deptName;

//    子节点
    private List<SysDept> children;
    }

创建数据库表

create table `ry-vue`.sys_dept
(
    dept_id     bigint auto_increment comment '部门id'
        primary key,
    parent_id   bigint      default 0   null comment '父部门id',
    ancestors   varchar(50) default ''  null comment '祖级列表',
    dept_name   varchar(30) default ''  null comment '部门名称',
    order_num   int(4)      default 0   null comment '显示顺序',
    leader      varchar(20)             null comment '负责人',
    phone       varchar(11)             null comment '联系电话',
    email       varchar(50)             null comment '邮箱',
    status      char        default '0' null comment '部门状态（0正常 1停用）',
    del_flag    char        default '0' null comment '删除标志（0代表存在 2代表删除）',
    create_by   varchar(64) default ''  null comment '创建者',
    create_time datetime                null comment '创建时间',
    update_by   varchar(64) default ''  null comment '更新者',
    update_time datetime                null comment '更新时间'
)
    comment '部门表' engine = InnoDB;

INSERT INTO `sys_dept` VALUES (100,0,'0','若依科技',0,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(101,100,'0,100','深圳总公司',1,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(102,100,'0,100','长沙分公司',2,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(103,101,'0,100,101','研发部门',1,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(104,101,'0,100,101','市场部门',2,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(105,101,'0,100,101','测试部门',3,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(106,101,'0,100,101','财务部门',4,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(107,101,'0,100,101','运维部门',5,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(108,102,'0,100,102','市场部门',1,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(109,102,'0,100,102','财务部门',2,'若依','15888888888','ry@qq.com','0','0','admin','2022-03-18 13:44:40','',NULL),(110,0,'','中软国际',0,NULL,NULL,NULL,'0','0','',NULL,'',NULL),(111,110,'','青岛分公司',0,NULL,NULL,NULL,'0','0','',NULL,'',NULL);

建立树形结构工具类

import com.example.demo.model.SysDept;
import java.util.ArrayList;
import java.util.List;

public class TreeNode {

    // 建立父节点树形结构
    public List<SysDept> buildTree(List<SysDept> depts){
        ArrayList<SysDept> sysDepts = new ArrayList<>();
        for (SysDept sysDept : getNodeTree(depts)) {
            getChildrenNode(depts, sysDept);
            sysDepts.add(sysDept);
        }
        return sysDepts;
    }
    // 查询所有的父节点，getParent()=0
    private List<SysDept> getNodeTree(List<SysDept> depts){
        ArrayList<SysDept> sysDepts = new ArrayList<>();
        for (SysDept dept : depts) {
            if (dept.getParentId()==0){
                sysDepts.add(dept);
            }
        }
        return sysDepts;
    }

    // 递归建立树形子节点，将子节点放到父节点下
    private SysDept getChildrenNode(List<SysDept> depts,SysDept sysDept){
        ArrayList<SysDept> sysDepts = new ArrayList<>();
        for (SysDept dept : depts) {
            if (dept.getParentId().equals(sysDept.getDeptId())){
                sysDepts.add(getChildrenNode(depts,dept));
            }
        }
        sysDept.setChildren(sysDepts);
        return sysDept;
    }
}

测试

import com.example.demo.mapper.SysDeptMapper;
import com.example.demo.model.SysDept;
import com.example.demo.node.TreeNode;
import net.minidev.json.JSONArray;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class SpringNodeApplicationTests {

    @Autowired
    private SysDeptMapper sysDeptMapper;
    @Test
    void contextLoads() {

        List<SysDept> sysDepts = sysDeptMapper.selectSysDept();
        TreeNode treeNode = new TreeNode();
        List<SysDept> sysDepts1 = treeNode.buildTree(sysDepts);
        String s = JSONArray.toJSONString(sysDepts1);
        System.out.println(s);
    }
}