技術標籤：javalambdalambdamap

封裝請求資料需要排序進行簽名，map如何排序？

• map資料封裝

  public static void main(String[] args) {
      Map<String, String> params = new HashMap<>();
      params.put("stu_no", "123456");
      params.put("stu_name", "穎寶");
      params.put("age"
   
  , "18");
      params.put("app_id", "1fb665aba37c437280c2c8e5cb1eff3b");
      params.put("timestamp", String.valueOf(System.currentTimeMillis() / 1000));
      formatParamMapToString(params, false, false);
      method1(params);
      method2(params);
      method3(params);
      method4
   
  (params);
      method5(params);
  }
  

• 藉助list方法、

 public static String formatParamMapToString(Map<String, String> paramMap, boolean urlEncode, boolean keyToLower) {
        // 原有方式排序
        try {
            List<String> paramList = new ArrayList<>();
            for (String key : paramMap.
 
keySet()) {
                paramList.add((keyToLower ? key.toLowerCase() : key) + "="
                        + (urlEncode ? URLEncoder.encode(paramMap.get(key), "utf-8") : paramMap.get(key)));
            }
            Collections.sort(paramList);
            System.out.println("原有藉助list排序paramList:" + paramList);

            StringBuilder beforeSign = new StringBuilder();
            for (String param : paramList) {
                beforeSign.append(param);
            }
            return beforeSign.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";
    }

• 方法1、

   private static void method1(Map<String, String> params) {
        // 自己寫的
        params = params.entrySet().stream().sorted((t1, t2) -> t1.getKey().compareTo(t2.getKey()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (v1, v2) -> v1, LinkedHashMap::new));
        System.out.println("自己寫的method1:" + params);
    }

• 方法2、

  private static void method2(Map<String, String> params) {
        // key 正序
        params = params.entrySet().stream().sorted(Map.Entry.comparingByKey(Comparator.naturalOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (v1, v2) -> v1, LinkedHashMap::new));
        System.out.println("採用函式key正序method2:" + params);
        // LinkedHashMap就是連結串列+散列表的結構，其底層採用了Linked雙向連結串列來儲存節點的訪問順序，所以保證了有序性。此處返回必須是LinkedHashMap，返回HashMap則無序。
    }

• 方法3、

  private static void method3(Map<String, String> params) {
        // key 倒序
        params = params.entrySet().stream().sorted(Map.Entry.comparingByKey(Comparator.reverseOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (v1, v2) -> v1, LinkedHashMap::new));
        // params.entrySet().forEach(entry -> System.out.println(String.format("%s=%s", entry.getKey(), entry.getValue())));
        System.out.println("採用函式key倒序method3:" + params);
    }

• 方法4、

  private static void method4(Map<String, String> params) {
        // value 正序
        params = params.entrySet().stream().sorted(Map.Entry.comparingByValue()) // Comparator.naturalOrder()可以不寫，預設正序
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (v1, v2) -> v1, LinkedHashMap::new));
        System.out.println("採用函式value正序:" + params);

    }

• 方法5、

 private static void method5(Map<String, String> params) {
        params = params.entrySet().stream().sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (v1, v2) -> v1, LinkedHashMap::new));
        System.out.println("採用函式value倒序:" + params);
    }

執行結果