Java封装树形结构数据

业务场景
进行业务开发时，有时前端需要一个树形导航菜单，或者分类菜单，这样就需要后端把数据封装成一个树形结构。比较常见的像导航菜单、省市区级联等。
在此模拟一个类似场景，查询部门信息，并且存在上下级。

实体类
实体类中使用parentCode来实现数据关联。

/**
 * @author Yoko
 * @date 2021/10/28
 */
@Data
@Builder
public class Department {
    /**
     * 公司编码
     */
    private Integer companyCode;
    /**
     * 部门名称
     */
    private String name;

    /**
     * 部门编码
     */
    private Integer code;

    /**
     * 上级部门编码
     */
    private Integer parentCode;

    /**
     * 部门下所管辖部门
     */
    private List<Department> children;
}

业务实现

public static void main(String[] args) {
         // 查询公司下所有部门信息
        List<com.hqins.ishare.user.demo.Department> departmentList = departmentListByCompanyCode();
        // 使用filter()过滤，获取最上层部门
        List<com.hqins.ishare.user.demo.Department> result = departmentList.stream().filter(depart -> 0 == depart.getParentCode())
                // 使用peek() 为上级部门添加下级部门
                .peek(depart -> depart.setChildren(createChildList(depart, departmentList)))
                // 排序
                .sorted(Comparator.comparing(com.hqins.ishare.user.demo.Department:: getCode))
                // 收集数据至list
                .collect(Collectors.toList());
        System.out.println(JSONObject.toJSONString(result));

    }
    /**
     * 递归获取
     * 根据当前部门，获取其子部门
     */
    private static List<com.hqins.ishare.user.demo.Department> createChildList(com.hqins.ishare.user.demo.Department father, List<com.hqins.ishare.user.demo.Department> list) {
        return list.stream().filter(model -> father.getCode().equals(model.getParentCode()))
                .peek(model -> model.setChildren(createChildList(model, list)))
                .sorted(Comparator.comparing(com.hqins.ishare.user.demo.Department:: getCode))
                .collect(Collectors.toList());
    }

    /**
     * 模拟数据库查询
     * 根据公司编码获取公司所有部门信息
     */
    private static List<com.hqins.ishare.user.demo.Department> departmentListByCompanyCode() {
        List<com.hqins.ishare.user.demo.Department> result = new ArrayList<>();
        com.hqins.ishare.user.demo.Department model1 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("技术部").code(10000).parentCode(0).build();
        com.hqins.ishare.user.demo.Department model2 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("java开发部").code(10001).parentCode(10000).build();
        com.hqins.ishare.user.demo.Department model3 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("前端技术部").code(10002).parentCode(10000).build();
        com.hqins.ishare.user.demo.Department model4 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("人事部").code(10003).parentCode(0).build();
        com.hqins.ishare.user.demo.Department model5 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("人事一部").code(10004).parentCode(10003).build();
        com.hqins.ishare.user.demo.Department model6 = com.hqins.ishare.user.demo.Department.builder().companyCode(10086).name("人事二部").code(10005).parentCode(10003).build();
        result.add(model1);
        result.add(model2);
        result.add(model3);
        result.add(model4);
        result.add(model5);
        result.add(model6);
        return result;
    }

数据结果

[{
	"children": [{
		"children": [],
		"code": 10001,
		"companyCode": 10086,
		"name": "java开发部",
		"parentCode": 10000
	}, {
		"children": [],
		"code": 10002,
		"companyCode": 10086,
		"name": "前端技术部",
		"parentCode": 10000
	}],
	"code": 10000,
	"companyCode": 10086,
	"name": "技术部",
	"parentCode": 0
}, {
	"children": [{
		"children": [],
		"code": 10004,
		"companyCode": 10086,
		"name": "人事一部",
		"parentCode": 10003
	}, {
		"children": [],
		"code": 10005,
		"companyCode": 10086,
		"name": "人事二部",
		"parentCode": 10003
	}],
	"code": 10003,
	"companyCode": 10086,
	"name": "人事部",
	"parentCode": 0
}]