签名算法

在调用接口进行编码前，开发者需先计算签名，计算方式如下：

• 把所有参数按照参数名首字母进行升序排序。(参数sign不参与签名)
• 对排序后的参数按照’key1=value1&key2=value2&key3=value3…’排列，生成字符串A。
• 将字符串A全部转化成小写字母，生成字符串B
• 在字符串B末尾拼接商户接口密钥(app_key)，生成字符串C。
• 对字符串C进行MD5计算，结果以小写表示。

将得到的签名赋给sign作为请求参数（空字符串也参与签名，如 key1=&key2=&key2=value2&... ）

签名代码如下(仅供参考)：

• 签名代码示例(PHP)：
  -------------------------------------------------------
      $post['customerId'] = 8000000;
      $post['page'] = 1;
      $post['pageSize'] = 20;
      $secret = "E36BC06C************3DBB33465";
      ksort($post);  //排序
      $sign_string = urldecode(http_build_query($post));
      $back_sign = md5(strtolower($sign_string) . $secret);
      $post['sign'] = $back_sign;
                          

• 签名代码示例(JAVA)：
  -------------------------------------------------------
      import java.security.MessageDigest;
      import java.security.NoSuchAlgorithmException;
      import java.util.HashMap;
      import java.util.Map;
      import java.util.TreeMap;
      import java.net.URLDecoder;
      import java.io.UnsupportedEncodingException;
      import java.util.stream.Collectors;
  
      public class SignGenerator {
          public static void main(String[] args) {
              Map post = new HashMap<>();
              post.put("customerId", 8000000);
              post.put("page", 1);
              post.put("pageSize", 20);
              String secret = "E36BC06C************3DBB33465";
  
              // Sort the parameters by key
              Map sortedPost = new TreeMap<>(post);
  
              // Build the query string
              String signString = sortedPost.entrySet().stream()
                      .map(entry -> entry.getKey() + "=" + entry.getValue())
                      .collect(Collectors.joining("&"));
  
              try {
                  // URL decode the string (similar to urldecode in PHP)
                  signString = URLDecoder.decode(signString, "UTF-8");
  
                  // Append the secret and convert to lowercase
                  String stringToSign = signString.toLowerCase() + secret;
  
                  // Calculate MD5 hash
                  String backSign = md5(stringToSign);
  
                  // Add the signature to the post data
                  post.put("sign", backSign);
  
                  System.out.println("Generated sign: " + backSign);
                  System.out.println("Final post data: " + post);
              } catch (UnsupportedEncodingException e) {
                  e.printStackTrace();
              }
          }
  
          private static String md5(String input) {
              try {
                  MessageDigest md = MessageDigest.getInstance("MD5");
                  byte[] messageDigest = md.digest(input.getBytes());
  
                  // Convert byte array to hex string
                  StringBuilder hexString = new StringBuilder();
                  for (byte b : messageDigest) {
                      String hex = Integer.toHexString(0xff & b);
                      if (hex.length() == 1) {
                          hexString.append('0');
                      }
                      hexString.append(hex);
                  }
                  return hexString.toString();
              } catch (NoSuchAlgorithmException e) {
                  throw new RuntimeException(e);
              }
          }
      }