如何用HashMap高效构建MySQL企业、部门、职位三级树状结构？

利用HashMap构建高效的MySQL企业、部门、职位三级树形结构

本文介绍如何使用HashMap高效地将MySQL数据库中的企业、部门、职位数据转换成树形结构。

核心思路：

采用两个HashMap分别存储公司和部门信息，通过一次遍历数据库结果集，构建完整的树形结构。

Java代码实现：

List companies = new ArrayList<>();
Company currentCompany;
Department currentDepartment;
Map companyMap = new HashMap<>();
Map departmentMap = new HashMap<>();

for (Po po : records) {
    // 处理公司信息
    String companyKey = po.getCompanyCode();
    if (companyMap.containsKey(companyKey)) {
        currentCompany = companyMap.get(companyKey);
    } else {
        currentCompany = new Company();
        currentCompany.setCode(po.getCompanyCode());
        currentCompany.setName(po.getCompanyName());
        companyMap.put(companyKey, currentCompany);
        companies.add(currentCompany);
    }

    // 处理部门信息
    String departmentKey = po.getCompanyCode() + po.getDeptCode();
    if (departmentMap.containsKey(departmentKey)) {
        currentDepartment = departmentMap.get(departmentKey);
    } else {
        currentDepartment = new Department();
        currentDepartment.setCode(po.getDeptCode());
        currentDepartment.setName(po.getDeptName());
        departmentMap.put(departmentKey, currentDepartment);
        currentCompany.getDepartments().add(currentDepartment);
    }

    // 处理职位信息
    Job job = new Job();
    job.setCode(po.getCode());
    job.setName(po.getJobName());
    currentDepartment.getJobs().add(job);
}

最终结果：

companies 列表将包含完整的树形结构数据，每个Company对象包含其下属部门列表，每个Department对象包含其下属职位列表。 此方法避免了递归查询，提高了效率。