1、部门的数据表中必须有“部门编号”和“父级部门编号”这两个字段，其余字段根据自己需要添加，如下图所示。parent_id就是父级部门编号。

 2、编写Department实体类，如下代码

package com.entity;
import org.joda.time.DateTime;
import java.util.List;

public class Department {
    private String id;
    private String name;
    private String parent_id;
    private Integer sequence;
    private Integer level;
    private Boolean enabled;
    private String operate_time;
    private List<Department> children;

    public List<Department> getChildren() {
        return children;
    }

    public void setChildren(List<Department> children) {
        this.children = children;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getParent_id() {
        return parent_id;
    }

    public void setParent_id(String parent_id) {
        this.parent_id = parent_id;
    }

    public Integer getSequence() {
        return sequence;
    }

    public void setSequence(Integer sequence) {
        this.sequence = sequence;
    }

    public Integer getLevel() {
        return level;
    }

    public void setLevel(Integer level) {
        this.level = level;
    }

    public Boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(Boolean enabled) {
        this.enabled = enabled;
    }

    public String getOperate_time() {
        return operate_time;
    }

    public void setOperate_time(String operate_time) {
        this.operate_time = operate_time;
    }
}

3、编写接口类，代码如下：

1 package com.repository;
2 import org.apache.ibatis.annotations.Mapper;
3 import java.util.List;
4 @Mapper
5 public interface DepartmentInterface {
6     public List<com.entity.Department> getDepartmentById(String id);
7 }

4、编写mapper.xml文件，此处采用了递归法。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.repository.DepartmentInterface">
    <resultMap id="BaseResultMap" type="com.entity.Department">
        <id property="id" column="id"/>
        <result column="name" property="name"/>
        <result column="parent_id" property="parent_id"/>
        <result column="operate_time" property="operate_time"/>
    </resultMap>

    <resultMap id="DepartmentWithChildren" type="com.entity.Department" extends="BaseResultMap">
        <collection column="id" ofType="com.entity.Department"
                    select="com.repository.DepartmentInterface.getDepartmentById" property="children">
        </collection>
    </resultMap>

    <select id="getDepartmentById" resultMap="DepartmentWithChildren">
        select dp.id,dp.name,dp.parent_id,dp.operate_time from sys_organization dp where dp.`parent_id`=#{id} and enabled=true order by sequence asc;
    </select>
</mapper>

5、编写控制类。

@RestController
public class DepartmentController {
    @Autowired DepartmentInterface dep;
    @RequestMapping("/department") //读取所有部门及其子部门
    public List<Department> getDepartment(){
        List<Department> dp= dep.getDepartmentById("0");
        return dp;
    }
}

6、页面输出结果

[{"id":"0000000001","name":"总公司","parent_id":"0","operate_time":"2021-11-15 20:46:12","children":[{"id":"0100000000","name":"分公司1","parent_id":"0000000001","children":[{"id":"0101000000","name":"部门1","parent_id":"0100000000","children":[]},{"id":"0102000000","name":"部门2","parent_id":"0100000000","children":[]}]},{"id":"0200000000","name":"分公司2","parent_id":"0000000001","children":[]}]}]