生成樹形菜單-通過兩個map集合

1.數據庫sql語句

 create table company(
   company_id           int                            not null auto_increment,
   parent_company_id    int                            null,
   name                 varchar(128)                   null,
   phone                varchar(16)                    null,
   constraint PK_COMPANY primary key clustered (company_id)
);

2.查詢語句DAO

public List<Company> getAllCompany() {
        List<Company> companies=null;
        String hql = "select c from Company c";
        Query query=getEntityManager().createQuery(hql);
        companies=query.getResultList();
        return companies;
    }

3.創建返回實體

public class CompanyTreeVo{
    private Integer companyId;
    private String name;
    private String phone;
    private List<CompanyTreeVo> children;//...getter/setter..}

3.組裝成tree-Service

        

public CompanyTreeVo findAllCompanyName() {
        List<Company> companies = companyDao.getAllCompany();
        if(companies!=null&&companies.size()>0) {
            Map<Integer, Company> objectMap = new HashMap<>();
            Map<Integer, List<Integer>> childMap = new HashMap<>();
            Integer rootId = CompanyFactory.checkTree(companies, childMap, objectMap);
            CompanyTreeVo treeVo = CompanyFactory.initTreeCompany(rootId, childMap, objectMap);
            return treeVo;
        }else{
            return null;
        }}

    public static Integer checkTree(List<Company> companies,Map<Integer,List<Integer>> childMap,Map<Integer,Company> objectMap){
        Map<Integer,CompanyMenuVo> maps=new HashMap<>();
        Integer rootId=null;
        CompanyMenuVo companyMenuVo=null;
        if(companies!=null &&companies.size()>0){//判斷查詢過來的值不爲空
            for(Company company :companies){//遍歷查詢的值
                objectMap.put(company.getCompanyId(),company);
                Integer parentId = company.getParentCompanyId();//獲取每個對象的父id
                if(parentId != null){//如果父id不爲null則進行下面操作
                    List<Integer> list = childMap.get(parentId);//獲取父id的集合是否初始化
                    if(list==null){
                        list = new ArrayList<>();
                    }
                    //將公司id添加集合中
                    list.add(company.getCompanyId());
                    //將集合添加到key爲父id的map中
                    childMap.put(parentId,list);
                }else{//父id初始化操作
                    rootId=company.getCompanyId();
                }
            }
        }
        return rootId;
    }

    public static CompanyTreeVo initTreeCompany(Integer rootId,Map<Integer,List<Integer>> childMap, Map<Integer,Company> objectMap){
        CompanyTreeVo rootVo = new CompanyTreeVo();
        List<CompanyTreeVo> children = new ArrayList<>();
        Company company = objectMap.get(rootId);
        //將實體對象轉換爲vo對象
        initCompanyTreeVo(rootVo, company);
        List<Integer> childList = childMap.get(rootId);
        if(childList!=null&&childList.size()>0){
            for(Integer  childId:childList){
                //遞歸將數據轉入list集合中
                CompanyTreeVo childTreeVo = initTreeCompany(childId, childMap, objectMap);
                childTreeVo.setParentCompanyName(company.getName());
                children.add(childTreeVo);
            }
        }
        rootVo.setChildren(children);
        return rootVo;
    }

    //將實體對象轉換爲vo對象
    public static void initCompanyTreeVo(CompanyTreeVo treeVo,Company company){
        treeVo.setCompanyId(company.getCompanyId());
        treeVo.setName(company.getName());
        treeVo.setParentCompanyId(company.getParentCompanyId());
    }