部门树形结构算法 — Java递归实现

将查询到的部门列表数据，进行父子节点树形结构排序
该功能适用需要树形结构的，不仅仅是部门树

步骤：

1. 查询数据库，获得所有的部门列表
2. 调用下面的实现方法

一、建表语句

CREATE TABLE `dept` (
  `deptId` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
  `name` varchar(32) DEFAULT NULL COMMENT '部门名称',
  `parentId` bigint(20) DEFAULT NULL COMMENT '父级部门ID',
  PRIMARY KEY (`deptId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

数据例如：

 

二、实现方法代码：

import com.alibaba.fastjson2.JSON;

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

public class demo {
    /**
     * 部门实体
     *
     */
    public static class Dept {

        /**
         * 部门id
         */
        private String deptId;

        /**
         * 部门名称
         */
        private String name;

        /**
         * 父部门id
         */
        private String parentId;

        /**
         * 子部门
         */
        private List<Dept> children = new ArrayList<>();

        public String getDeptId() {
            return deptId;
        }

        public void setDeptId(String deptId) {
            this.deptId = deptId;
        }

        public String getName() {
            return name;
        }

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

        public String getParentId() {
            return parentId;
        }

        public void setParentId(String parentId) {
            this.parentId = parentId;
        }

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

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

    public static void main(String[] arg) {
        List<Dept> deptList = new ArrayList<>();
        //添加第一级
        Dept dept = new Dept();
        dept.setDeptId("1000");
        dept.setParentId("0");
        dept.setName("康复中心门诊");
        deptList.add(dept);

        Dept dept1 = new Dept();
        dept1.setDeptId("1001");
        dept1.setParentId("0");
        dept1.setName("妇产科");
        deptList.add(dept1);

        Dept dept2 = new Dept();
        dept2.setDeptId("1002");
        dept2.setParentId("0");
        dept2.setName("骨伤科");
        deptList.add(dept2);

        //添加第二级
        Dept dept3 = new Dept();
        dept3.setDeptId("10021");
        dept3.setParentId("1002");
        dept3.setName("颈肩腰腿痛专科门诊");
        deptList.add(dept3);

        Dept dept4 = new Dept();
        dept4.setDeptId("10022");
        dept4.setParentId("1002");
        dept4.setName("骨伤二科（康复六科）门诊");
        deptList.add(dept4);

        Dept dept5 = new Dept();
        dept5.setDeptId("10001");
        dept5.setParentId("1000");
        dept5.setName("肌骨疼痛康复门诊");
        deptList.add(dept5);

        Dept dept6 = new Dept();
        dept6.setDeptId("10002");
        dept6.setParentId("1000");
        dept6.setName("脑卒中康复门诊");
        deptList.add(dept6);

        //添加第三级
        Dept dept7 = new Dept();
        dept7.setDeptId("100021");
        dept7.setParentId("10002");
        dept7.setName("脑卒中康复门诊-小门诊");
        deptList.add(dept7);

        Dept dept8 = new Dept();
        dept8.setDeptId("100022");
        dept8.setParentId("10002");
        dept8.setName("脑卒中康复门诊-小门诊-小小门诊");
        deptList.add(dept8);

        List<Dept> deptListNew = buildDeptTree(deptList);
        System.out.println(deptListNew.size());
        for (Dept dept9 : deptListNew) {
            System.out.println("一级信息：" + JSON.toJSONString(dept9));
            if (hasChild(dept9.getChildren(), dept9)) {
                for (Dept dept10 : dept9.getChildren()) {
                    //System.out.println("二级信息：" + JSON.toJSONString(dept10));
                    if (hasChild(dept10.getChildren(), dept10)) {
                        for (Dept dept11 : dept10.getChildren()) {
                            //System.out.println("三级信息：" + JSON.toJSONString(dept11));
                        }
                    }
                }
            }
        }
        //3
        //一级信息：{"children":[{"children":[],"deptId":"10001","name":"肌骨疼痛康复门诊","parentId":"1000"},{"children":[{"children":[],"deptId":"100021","name":"脑卒中康复门诊-小门诊","parentId":"10002"},{"children":[],"deptId":"100022","name":"脑卒中康复门诊-小门诊-小小门诊","parentId":"10002"}],"deptId":"10002","name":"脑卒中康复门诊","parentId":"1000"}],"deptId":"1000","name":"康复中心门诊","parentId":"0"}
        //一级信息：{"children":[],"deptId":"1001","name":"妇产科","parentId":"0"}
        //一级信息：{"children":[{"children":[],"deptId":"10021","name":"颈肩腰腿痛专科门诊","parentId":"1002"},{"children":[],"deptId":"10022","name":"骨伤二科（康复六科）门诊","parentId":"1002"}],"deptId":"1002","name":"骨伤科","parentId":"0"}
    }

    /**
     * 构建前端所需要树结构
     *
     * @param depts 部门列表
     * @return 树结构列表
     */
    public static List<Dept> buildDeptTree(List<Dept> depts) {
        List<Dept> deptList = new ArrayList<>();
        List<String> deptIdList = new ArrayList<>();
        for (Dept dept : depts) {
            deptIdList.add(dept.getDeptId());
        }
        for (Dept dept : depts) {
            // 如果是顶级节点，遍历该父节点所有子节点
            if (!deptIdList.contains(dept.getParentId())) {
                recursionFn(depts, dept);
                deptList.add(dept);
            }
        }
        if (deptList.isEmpty()) {
            deptList = depts;
        }
        return deptList;
    }

    /**
     * 递归列表
     * 结束条件为所遍历的节点无下一级节点
     *
     * @param list 查询获得的所有部门数据
     * @param dept 顶级节点
     */
    private static void recursionFn(List<Dept> list, Dept dept) {
        // 得到子节点列表
        List<Dept> childList = getChildList(list, dept);
        dept.setChildren(childList);
        for (Dept tChild : childList) {
            // 如果子节点有下一级节点，得到下一级的节点列表
            if (hasChild(list, tChild)) {
                recursionFn(list, tChild);
            }
        }
    }

    /**
     * 获得该节点的下一级子节点列表
     *
     * @param list 查询获得的所有部门数据
     * @param dept 顶级节点
     * @return 顶级节点的下一级子节点列表
     */
    private static List<Dept> getChildList(List<Dept> list, Dept dept) {
        List<Dept> deptList = new ArrayList<>();
        for (Dept d : list) {
            // 遍历非顶级节点，并获得传入参数顶级节点的下一级子节点列表
            if (d.getParentId() != null && d.getParentId().equals(dept.getDeptId())) {
                deptList.add(d);
            }
        }
        return deptList;
    }

    /**
     * 判断是否有子节点
     *
     * @param list 节点列表
     * @param dept 部门节点
     * @return Boolean
     */
    private static boolean hasChild(List<Dept> list, Dept dept) {
        return getChildList(list, dept).size() > 0;
    }
    
}