mySql+Hibernate 单表上下级关系数据整理

table
id classname parent_id
1 服装 null
2 男装 1
3 女装 1
4 男裤 2
5 男上衣 2
…….

/** * 商品分类实体类 */@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)@Entity@Table(name = "wemall_goodsclass")public class GoodsClass extends IdEntity {    private static final long serialVersionUID = 1L;    //分类名称    private String className;    //商品子分类    @OneToMany(mappedBy = "parent")    @OrderBy("sequence asc")    private List<GoodsClass> childs = new ArrayList<GoodsClass>();    //商品父类    @ManyToOne(fetch = FetchType.LAZY)    private GoodsClass parent;    private int sequence;    //等级等级    private int level;    .......省略其他字段以及get set方法@Autowired    private IGoodsClassService goodsClassService;    @RequestMapping({ "/user/goodsclass.htm" })    private void getGoodsClass(HttpServletRequest request, HttpServletResponse response) {        Map<String, String> resultMap = new HashMap<>();        Map params = new HashMap();        params.put("display", Boolean.valueOf(true));        List<GoodsClass> gcs = this.goodsClassService.query(                "select obj from GoodsClass obj where obj.parent.id is null and obj.display=:display order by obj.sequence asc",                params, -1, -1);        if (gcs.size() < 0) {            resultMap.put("code", "102");            resultMap.put("msg", "查无数据");            writeResponse(response, resultMap);        } else {            stringify(response, gcs);        }    }    /**     * 把对象转换为json字符串 输出     * @param goodsClass  商品类型对象     */    private void stringify(HttpServletResponse response,List<GoodsClass> goodsClass) {        // 商品        // ---> 商品子分类        // ---> 商品子分类        JSONArray list = new JSONArray();        for (GoodsClass firstGoodsClass : goodsClass) { // 迭代第一层商品类型            JSONObject firstMap = new JSONObject(); // 存储第一层商品类型            firstMap.put("id", firstGoodsClass.getId());            firstMap.put("className", firstGoodsClass.getClassName());            List<GoodsClass> sencondGoodsClassList = firstGoodsClass.getChilds(); // 获取第一层商品类型的子分类            JSONArray sencondList = new JSONArray();            for (GoodsClass sencondGoodsClass : sencondGoodsClassList) {// 迭代第一层子分类                JSONObject sencondMap = new JSONObject();                sencondMap.put("id", sencondGoodsClass.getId());                sencondMap.put("className", sencondGoodsClass.getClassName());                List<GoodsClass> thirdGoodsClassList = sencondGoodsClass.getChilds(); // 获取第二层子分类                JSONArray thirdList = new JSONArray();                for (GoodsClass thirdGoodsClass : thirdGoodsClassList) { // 迭代第二层子分类                    JSONObject thirdMap = new JSONObject();                    thirdMap.put("id", thirdGoodsClass.getId());                    thirdMap.put("className", thirdGoodsClass.getClassName());                    thirdList.add(thirdMap); // 将每个第二层的子分类存储到第二层子分类列表中                }                sencondMap.put("childGoodsClass", thirdList); // 将第二层子分类列表存储在第一层子分类中                sencondList.add(sencondMap); // 将第一层子分类存储在第一层子分类列表            }            firstMap.put("childGoodsClass", sencondList); // 将第二层子分类列表存储在第一层商品分类中            list.add(firstMap);        }        Gson gson = new Gson();        PrintWriter writer = getPrintWriter(response);        writer.print(gson.toJson(list));    }    /**     *      * @param response     * @param map     */    private void writeResponse(HttpServletResponse response, Map<String, String> map) {        Gson gson = new Gson();        PrintWriter writer = getPrintWriter(response);        writer.print(gson.toJson(map));    }    private PrintWriter getPrintWriter(HttpServletResponse response) {        response.setContentType("text/plain");        response.setHeader("Cache-Control", "no-cache");        response.setCharacterEncoding("UTF-8");        try {            return response.getWriter();        } catch (IOException e) {            e.printStackTrace();        }        return null;    }-----------------------------------------------分割线递归循环获取方法    @RequestMapping(value = "/DagTree")    public void tree(HttpServletRequest request, HttpServletResponse response) throws Exception {        Map params = HtmlUtil.getParameterMap(request);        List<Map<String, Object>> lst = getCJtreeList(params);        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();        Map kqgz_map = new HashMap();        kqgz_map.put("children", lst);        kqgz_map.put("id", "-1");        kqgz_map.put("text", "库房结构树");        kqgz_map.put("state", "open");        kqgz_map.put("sfkf", "0");        list.add(kqgz_map);        HtmlUtil.writerJson(response, list);    }    private List<Map<String, Object>> getCJtreeList(Map paramMap) throws Exception {        List<Map<String, Object>> result = new ArrayList<Map<String, Object>>();        result = baseService.selectList("com.kq.dagl.dakgl.DAGL_DagTree", paramMap);        List<Map<String, Object>> LIST_CJ = result;        result = this.iteration("", LIST_CJ);//上级ID为0 表示最高级别        LIST_CJ = result;        return LIST_CJ;    }