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Object Storage Service:表單上傳

更新時間:May 16, 2025

OSS表單上傳允許網頁應用通過標準HTML表單直接將檔案上傳至OSS。這種方式下,在前端頁面選擇檔案後,瀏覽器發起POST請求直接將檔案傳輸到OSS伺服器,而無需經過網站伺服器中轉,減輕了伺服器的壓力,提高了檔案上傳的效率和穩定性。

使用限制

通過表單上傳的方式上傳的Object大小不能超過5 GB。

使用情境

表單上傳廣泛應用於Web應用程式,包括但不限於以下幾個方面:

  • 使用者資料上傳:註冊帳號時上傳頭像、身份證照片或其他身分識別驗證材料。在個人中心修改資訊時上傳新的頭像或背景圖。

  • 檔案分享與儲存:在網盤服務、協同辦公平台等通過表單上傳各種格式的檔案,如文檔、圖片、音頻、視頻等至雲端進行儲存和共用。

  • 內容創作與發布:在部落格、論壇、問答社區等平台編寫文章並通過表單上傳圖片、附件等作為內容補充。

  • 電商管理:商家在電商平台後台上傳商品圖片、詳細描述檔案、資質認證等;買家在購買過程中上傳發票需求或其他證明材料。

  • 線上教育平台:學生在提交作業或專案時上傳文檔、PPT、視頻等作業檔案;教師在課程建設時上傳教學資料、課件等。

  • 求職招聘網站:求職者上傳簡曆、作品集等求職材料;企業發布職位時上傳公司LOGO、招聘資訊檔等。

  • 問卷調查與反饋:填寫線上調查問卷時上傳附加的證據檔案或說明文檔。

  • 軟體開發協作:在代碼託管平台如GitHub、GitLab等上傳代碼檔案或專案文檔。

方案概述

您可以在服務端產生PostObject所需的Post簽名、PostPolicy等資訊,然後用戶端可以憑藉這些資訊,在一定的限制下不依賴OSS SDK直接上傳檔案。您可以藉助服務端產生的PostPolicy限制用戶端上傳的檔案,例如限制檔案大小、檔案類型。此方案適用於通過HTML表單上傳的方式上傳檔案。需要注意的是,此方案不支援基於分區上傳大檔案、基於分區斷點續傳的情境。更多資訊,請參見PostObject

服務端通過Post簽名和Post Policy授權用戶端上傳檔案到OSS的過程如下。

  1. 用戶端向商務服務器請求Post簽名和Post Policy等資訊。

  2. 商務服務器產生並返回Post簽名和Post Policy等資訊給用戶端。

  3. 用戶端使用Post簽名和Post Policy等資訊調用PostObject通過HTML表單的方式上傳檔案到OSS。

  4. OSS返回成功響應給用戶端。

操作步驟

  1. 服務端產生Post簽名和Post Policy等資訊。

    • 樣本工程:postsignature.zip

    • 範例程式碼

      服務端產生Post簽名和Post Policy等資訊的範例程式碼如下:

      Python

      import os
      from hashlib import sha1 as sha
      import json
      import base64
      import hmac
      import datetime
      import time
      
      # 配置環境變數OSS_ACCESS_KEY_ID。
      access_key_id = os.environ.get('OSS_ACCESS_KEY_ID')
      # 配置環境變數OSS_ACCESS_KEY_SECRET。
      access_key_secret = os.environ.get('OSS_ACCESS_KEY_SECRET')
      # 將<YOUR_BUCKET>替換為Bucket名稱。
      bucket = '<YOUR_BUCKET>'
      # host的格式為bucketname.endpoint。將<YOUR_BUCKET>替換為Bucket名稱。將<YOUR_ENDPOINT>替換為OSS Endpoint,例如oss-cn-hangzhou.aliyuncs.com。
      host = 'https://<YOUR_BUCKET>.<YOUR_ENDPOINT>'
      # 指定上傳到OSS的檔案首碼。
      upload_dir = 'user-dir-prefix/'
      # 指定到期時間,單位為秒。
      expire_time = 3600
      
      
      def generate_expiration(seconds):
          """
          通過指定有效時間長度(秒)產生到期時間。
          :param seconds: 有效時間長度(秒)。
          :return: ISO8601 時間字串,如:"2014-12-01T12:00:00.000Z"。
          """
          now = int(time.time())
          expiration_time = now + seconds
          gmt = datetime.datetime.utcfromtimestamp(expiration_time).isoformat()
          gmt += 'Z'
          return gmt
      
      
      def generate_signature(access_key_secret, expiration, conditions, policy_extra_props=None):
          """
          產生簽名字串Signature。
          :param access_key_secret: 有許可權訪問目標Bucket的AccessKeySecret。
          :param expiration: 簽名到期時間,按照ISO8601標準表示,並需要使用UTC時間,格式為yyyy-MM-ddTHH:mm:ssZ。樣本值:"2014-12-01T12:00:00.000Z"。
          :param conditions: 策略條件,用於限制上傳表單時允許設定的值。
          :param policy_extra_props: 額外的policy參數,後續如果policy新增參數支援,可以在通過dict傳入額外的參數。
          :return: signature,簽名字串。
          """
          policy_dict = {
              'expiration': expiration,
              'conditions': conditions
          }
          if policy_extra_props is not None:
              policy_dict.update(policy_extra_props)
          policy = json.dumps(policy_dict).strip()
          policy_encode = base64.b64encode(policy.encode())
          h = hmac.new(access_key_secret.encode(), policy_encode, sha)
          sign_result = base64.b64encode(h.digest()).strip()
          return sign_result.decode()
      
      def generate_upload_params():
          policy = {
              # 有效期間。
              "expiration": generate_expiration(expire_time),
              # 約束條件。
              "conditions": [
                  # 未指定success_action_redirect時,上傳成功後的返回狀態代碼,預設為 204。
                  ["eq", "$success_action_status", "200"],
                  # 表單域的值必須以指定首碼開始。例如指定key的值以user/user1開始,則可以寫為["starts-with", "$key", "user/user1"]。
                  ["starts-with", "$key", upload_dir],
                  # 限制上傳Object的最小和最大允許大小,單位為位元組。
                  ["content-length-range", 1, 1000000],
                  # 限制上傳的檔案為指定的圖片類型
                  ["in", "$content-type", ["image/jpg", "image/png"]]
              ]
          }
          signature = generate_signature(access_key_secret, policy.get('expiration'), policy.get('conditions'))
          response = {
              'policy': base64.b64encode(json.dumps(policy).encode('utf-8')).decode(),
              'ossAccessKeyId': access_key_id,
              'signature': signature,
              'host': host,
              'dir': upload_dir
              # 可以在這裡再自行追加其他參數
          }
          return json.dumps(response)
      

      Java

      import com.aliyun.help.demo.uploading_to_oss_directly_postsignature.config.OssConfig;
      import com.aliyun.oss.ClientException;
      import com.aliyun.oss.OSS;
      import com.aliyun.oss.OSSException;
      import com.aliyun.oss.common.utils.BinaryUtil;
      import com.aliyun.oss.model.MatchMode;
      import com.aliyun.oss.model.PolicyConditions;
      import org.springframework.beans.factory.annotation.Autowired;
      import org.springframework.stereotype.Controller;
      import org.springframework.web.bind.annotation.GetMapping;
      import org.springframework.web.bind.annotation.ResponseBody;
      import org.codehaus.jettison.json.JSONObject;
      import java.util.Date;
      import com.aliyun.oss.OSSClientBuilder;
      import org.springframework.context.annotation.Configuration;
      import org.springframework.context.annotation.Bean;
      import javax.annotation.PreDestroy;
      
      @Controller
      public class PostSignatureController {
          @Autowired
          private OSS ossClient;
      
          @Autowired
          private OssConfig ossConfig;
      
          @GetMapping("/get_post_signature_for_oss_upload")
          @ResponseBody
          public String generatePostSignature() {
              JSONObject response = new JSONObject();
              try {
                  long expireEndTime = System.currentTimeMillis() + ossConfig.getExpireTime() * 1000;
                  Date expiration = new Date(expireEndTime);
                  PolicyConditions policyConds = new PolicyConditions();
                  policyConds.addConditionItem(PolicyConditions.COND_CONTENT_LENGTH_RANGE, 0, 1048576000);
                  policyConds.addConditionItem(MatchMode.StartWith, PolicyConditions.COND_KEY, ossConfig.getDir());
                  String postPolicy = ossClient.generatePostPolicy(expiration, policyConds);
                  byte[] binaryData = postPolicy.getBytes("utf-8");
                  String encodedPolicy = BinaryUtil.toBase64String(binaryData);
                  String postSignature = ossClient.calculatePostSignature(postPolicy);
                  response.put("ossAccessKeyId", ossConfig.getAccessKeyId());
                  response.put("policy", encodedPolicy);
                  response.put("signature", postSignature);
                  response.put("dir", ossConfig.getDir());
                  response.put("host", ossConfig.getHost());
              } catch (
          OSSException oe) {
              System.out.println("Caught an OSSException, which means your request made it to OSS, "
                      + "but was rejected with an error response for some reason.");
              // 假設此方法存在
              System.out.println("HTTP Status Code: " + oe.getRawResponseError()); 
              System.out.println("Error Message: " + oe.getErrorMessage());
              System.out.println("Error Code:       " + oe.getErrorCode());
              System.out.println("Request ID:      " + oe.getRequestId());
              System.out.println("Host ID:           " + oe.getHostId());
          } catch (ClientException ce) {
              System.out.println("Caught an ClientException, which means the client encountered "
                      + "a serious internal problem while trying to communicate with OSS, "
                      + "such as not being able to access the network.");
              System.out.println("Error Message: " + ce.getMessage());
          } finally {
              if (ossClient != null) {
                  ossClient.shutdown();
              }
              return response.toString();
          }
        }
      }
      
      @Configuration
      public class OssConfig {
          /**
           * 將 <YOUR-ENDPOINT> 替換為 Endpoint,例如 oss-cn-hangzhou.aliyuncs.com
           */
          private String endpoint = "<YOUR-ENDPOINT>";
          /**
           * 將 <YOUR-BUCKET> 替換為 Bucket 名稱
           */
          private String bucket = "<YOUR-BUCKET>";
          /**
           * 指定上傳到 OSS 的檔案首碼
           */
          private String dir = "user-dir-prefix/";
          /**
           * 指定到期時間,單位為秒
           */
          private long expireTime = 3600;
          /**
           * 構造 host
           */
          private String host = "http://" + bucket + "." + endpoint;
          /**
           * 通過環境變數 ALIBABA_CLOUD_ACCESS_KEY_ID 設定 accessKeyId
           */
          private String accessKeyId = System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID");
          /**
           * 通過環境變數 ALIBABA_CLOUD_ACCESS_KEY_SECRET 設定 accessKeySecret
           */
          private String accessKeySecret = System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET");
      
          private OSS ossClient;
          @Bean
          public OSS getOssClient() {
              ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
              return ossClient;
          }
          @Bean
          public String getHost() {
              return host;
          }
          @Bean
          public String getAccessKeyId() {
              return accessKeyId;
          }
          @Bean
          public long getExpireTime() {
              return expireTime;
          }
          @Bean
          public String getDir() {
              return dir;
          }
      
          @PreDestroy
          public void onDestroy() {
              ossClient.shutdown();
          }
      }
      
      

      Go

      package main
      
      import (
      	"crypto/hmac"
      	"crypto/sha1"
      	"encoding/base64"
      	"encoding/json"
      	"fmt"
      	"io"
      	"net/http"
      	"os"
      	"time"
      )
      
      var (
      	// 配置環境變數OSS_ACCESS_KEY_ID。
      	accessKeyId = os.Getenv("OSS_ACCESS_KEY_ID")
      	// 配置環境變數OSS_ACCESS_KEY_SECRET。
      	accessKeySecret = os.Getenv("OSS_ACCESS_KEY_SECRET")
      	// host的格式為bucketname.endpoint。將${your-bucket}替換為Bucket名稱。將${your-endpoint}替換為OSS Endpoint,例如oss-cn-hangzhou.aliyuncs.com。
      	host = "http://${your-bucket}.${your-endpoint}"
      	// 指定上傳到OSS的檔案首碼。
      	uploadDir = "user-dir-prefix/"
      	// 指定到期時間,單位為秒。
      	expireTime = int64(3600)
      )
      
      type ConfigStruct struct {
      	Expiration string          `json:"expiration"`
      	Conditions [][]interface{} `json:"conditions"`
      }
      
      type PolicyToken struct {
      	AccessKeyId string `json:"ossAccessKeyId"`
      	Host        string `json:"host"`
      	Signature   string `json:"signature"`
      	Policy      string `json:"policy"`
      	Directory   string `json:"dir"`
      }
      
      func getGMTISO8601(expireEnd int64) string {
      	return time.Unix(expireEnd, 0).UTC().Format("2006-01-02T15:04:05Z")
      }
      
      func getPolicyToken() string {
      	now := time.Now().Unix()
      	expireEnd := now + expireTime
      	tokenExpire := getGMTISO8601(expireEnd)
      
      	var config ConfigStruct
      	config.Expiration = tokenExpire
      
      	// 添加檔案首碼限制
      	config.Conditions = append(config.Conditions, []interface{}{"starts-with", "$key", uploadDir})
      
      	// 添加檔案大小限制,例如1KB到10MB
      	minSize := int64(1024)
      	maxSize := int64(10 * 1024 * 1024)
      	config.Conditions = append(config.Conditions, []interface{}{"content-length-range", minSize, maxSize})
      
      	result, err := json.Marshal(config)
      	if err != nil {
      		fmt.Println("callback json err:", err)
      		return ""
      	}
      
      	encodedResult := base64.StdEncoding.EncodeToString(result)
      	h := hmac.New(sha1.New, []byte(accessKeySecret))
      	io.WriteString(h, encodedResult)
      	signedStr := base64.StdEncoding.EncodeToString(h.Sum(nil))
      
      	policyToken := PolicyToken{
      		AccessKeyId: accessKeyId,
      		Host:        host,
      		Signature:   signedStr,
      		Policy:      encodedResult,
      		Directory:   uploadDir,
      	}
      
      	response, err := json.Marshal(policyToken)
      	if err != nil {
      		fmt.Println("json err:", err)
      		return ""
      	}
      
      	return string(response)
      }
      
      func handler(w http.ResponseWriter, r *http.Request) {
      	if r.URL.Path == "/" {
      		http.ServeFile(w, r, "templates/index.html")
      		return
      	} else if r.URL.Path == "/get_post_signature_for_oss_upload" {
      		policyToken := getPolicyToken()
      		w.Header().Set("Content-Type", "application/json")
      		w.Write([]byte(policyToken))
      		return
      	}
      	http.NotFound(w, r)
      }
      
      func main() {
      	http.HandleFunc("/", handler)
      	http.ListenAndServe(":8080", nil)
      }
      

      PHP

      <?php
      function gmt_iso8601($time)
      {
          return str_replace('+00:00', '.000Z', gmdate('c', $time));
      }
      
      // 從環境變數中擷取訪問憑證。運行本範例程式碼之前,請確保已設定環境變數ALIBABA_CLOUD_ACCESS_KEY_ID和ALIBABA_CLOUD_ACCESS_KEY_SECRET。
      $accessKeyId = getenv("ALIBABA_CLOUD_ACCESS_KEY_ID");
      $accessKeySecret = getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET");
      // $host的格式為<YOUR-BUCKET>.<YOUR-ENDPOINT>',請替換為您的真實資訊。
      $host = 'http://<YOUR-BUCKET>.<YOUR-ENDPOINT>';
      // 使用者上傳檔案時指定的首碼。
      $dir = 'user-dir-prefix/';          
      
      $now = time();
      //設定該policy逾時時間是10s. 即這個policy過了這個有效時間,將不能訪問。
      $expire = 30;  
      $end = $now + $expire;
      $expiration = gmt_iso8601($end);
      
      //最大檔案大小.使用者可以自己設定。
      $condition = array(0 => 'content-length-range', 1 => 0, 2 => 1048576000);
      $conditions[] = $condition;
      
      // 表示使用者上傳的資料,必須是以$dir開始,不然上傳會失敗,這一步不是必須項,只是為了安全起見,防止使用者通過policy上傳到別人的目錄。
      $start = array(0 => 'starts-with', 1 => '$key', 2 => $dir);
      $conditions[] = $start;
      
      
      $arr = array('expiration' => $expiration, 'conditions' => $conditions);
      $policy = json_encode($arr);
      $base64_policy = base64_encode($policy);
      $string_to_sign = $base64_policy;
      $signature = base64_encode(hash_hmac('sha1', $string_to_sign, $accessKeySecret, true));
      
      $response = array();
      $response['ossAccessKeyId'] = $accessKeyId;
      $response['host'] = $host;
      $response['policy'] = $base64_policy;
      $response['signature'] = $signature;
      $response['dir'] = $dir;  
      echo json_encode($response);
      

      Node.js

      const express = require("express");
      const { Buffer } = require("buffer");
      const OSS = require("ali-oss");
      const app = express();
      const path = require("path");
      const config = {
        // 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_ID。
        accessKeyId: process.env.ALIBABA_CLOUD_ACCESS_KEY_ID,
        // 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_SECRET。
        accessKeySecret: process.env.ALIBABA_CLOUD_ACCESS_KEY_SECRET,
        // 將<YOUR-BUCKET>替換為Bucket名稱。
        bucket: "<YOUR-BUCKET>",
        // 指定上傳到OSS的檔案首碼。
        dir: "prefix/",
      };
      
      app.use(express.static(path.join(__dirname, "templates")));
      
      app.get("/get_post_signature_for_oss_upload", async (req, res) => {
        const client = new OSS(config);
        const date = new Date();
        // 設定簽名的有效期間,單位為秒。
        date.setSeconds(date.getSeconds() + 3600);
        const policy = {
          expiration: date.toISOString(),
          conditions: [
            // 設定上傳檔案的大小限制。
            ["content-length-range", 0, 1048576000],
            // 限制可上傳的Bucket。
            { bucket: client.options.bucket },
          ],
        };
        const formData = await client.calculatePostSignature(policy);
        const host = `http://${config.bucket}.${
          (await client.getBucketLocation()).location
        }.aliyuncs.com`.toString();
        const params = {
          policy: formData.policy,
          signature: formData.Signature,
          ossAccessKeyId: formData.OSSAccessKeyId,
          host,
          dir: config.dir,
        };
        res.json(params);
      });
      
      app.get(/^(.+)*\.(html|js)$/i, async (req, res) => {
        res.sendFile(path.join(__dirname, "./templates", req.originalUrl));
      });
      
      app.listen(8000, () => {
        console.log("http://127.0.0.1:8000");
      });
      

      Ruby

      require 'sinatra'
      require 'base64'
      require 'open-uri'
      require 'cgi'
      require 'openssl'
      require 'json'
      require 'sinatra/reloader'
      require 'sinatra/content_for'
      
      # 設定public檔案夾路徑為當前檔案夾下的templates檔案夾
      set :public_folder, File.dirname(__FILE__) + '/templates'
      
      # 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_ID。
      $access_key_id = ENV['ALIBABA_CLOUD_ACCESS_ID']
      # 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_SECRET。
      $access_key_secret = ENV['ALIBABA_CLOUD_ACCESS_SECRET']
      
      # $host的格式為<bucketname>.<endpoint>,請替換為您的真實資訊。
      $host = 'http://<bucketname>.<endpoint>';
      
      # 使用者上傳檔案時指定的首碼。
      $upload_dir = 'user-dir-prefix/'
      # 到期時間,單位為秒。
      $expire_time = 30
      $server_ip = "0.0.0.0"
      $server_port = 8000
      
      if ARGV.length == 1 
        $server_port = ARGV[0]
      elsif ARGV.length == 2
        $server_ip = ARGV[0]
        $server_port = ARGV[1]
      end
      
      puts "App server is running on: http://#{$server_ip}:#{$server_port}"
      
      def hash_to_jason(source_hash)
        jason_string = source_hash.to_json;    
      
        jason_string.gsub!("\":[", "\": [")
        jason_string.gsub!("\",\"", "\", \"")
        jason_string.gsub!("],\"", "], \"")
        jason_string.gsub!("\":\"", "\": \"")
      
        jason_string
      end
      
      
      def get_token()
        expire_syncpoint = Time.now.to_i + $expire_time
        expire = Time.at(expire_syncpoint).utc.iso8601()
        response.headers['expire'] = expire
        policy_dict = {}
        condition_arrary = Array.new
        array_item = Array.new
        array_item.push('starts-with')
        array_item.push('$key')
        array_item.push($upload_dir)
        condition_arrary.push(array_item)
        policy_dict["conditions"] = condition_arrary
        policy_dict["expiration"] = expire
        policy = hash_to_jason(policy_dict)
        policy_encode = Base64.strict_encode64(policy).chomp;
        h = OpenSSL::HMAC.digest('sha1', $access_key_secret, policy_encode)
        hs = Digest::MD5.hexdigest(h)
        sign_result = Base64.strict_encode64(h).strip()
        token_dict = {}
        token_dict['ossAccessKeyId'] = $access_key_id
        token_dict['host'] = $host
        token_dict['policy'] = policy_encode
        token_dict['signature'] = sign_result 
        token_dict['expire'] = expire_syncpoint
        token_dict['dir'] = $upload_dir
        result = hash_to_jason(token_dict)
        result
      end
      
      set :bind, $server_ip
      set :port, $server_port
      
      get '/get_post_signature_for_oss_upload' do
        token = get_token()
        puts "Token: #{token}"
        token
      end
      
      get '/*' do
        puts "********************* GET "
        send_file File.join(settings.public_folder, 'index.html')
      end
      
      end
      
      if ARGV.length == 1 
        $server_port = ARGV[0]
      elsif ARGV.length == 2
        $server_ip = ARGV[0]
        $server_port = ARGV[1]
      end
      
      $server_ip = "0.0.0.0"
      $server_port = 8000
      
      puts "App server is running on: http://#{$server_ip}:#{$server_port}"
      
      set :bind, $server_ip
      set :port, $server_port
      
      get '/get_sts_token_for_oss_upload' do
        token = get_sts_token_for_oss_upload()
        response = {
          "accessKeyId" => token["Credentials"]["AccessKeyId"],
          "accessKeySecret" => token["Credentials"]["AccessKeySecret"],
          "securityToken" => token["Credentials"]["SecurityToken"]
        }
        response.to_json
      end
      
      get '/*' do
        puts "********************* GET "
        send_file File.join(settings.public_folder, 'index.html')
      end
      

      C#

      using Microsoft.AspNetCore.Builder;
      using Microsoft.Extensions.DependencyInjection;
      using Microsoft.AspNetCore.Http;
      using System.IO;
      using System.Collections.Generic;
      using System;
      using System.Globalization;
      using System.Text;
      using System.Security.Cryptography;
      using Newtonsoft.Json;
      using Microsoft.AspNetCore.Http.Extensions;
      using Microsoft.AspNetCore.Mvc;
      using Microsoft.Extensions.Logging;
      
      namespace YourNamespace
      {
          public class Program
          {
              private ILogger<Program> _logger;
              // 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_ID。
              public string AccessKeyId { get; set; } = Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_ID");
              // 配置環境變數ALIBABA_CLOUD_ACCESS_KEY_SECRET。
              public string AccessKeySecret { get; set; } = Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_SECRET");
              // host的格式為bucketname.endpoint。將<YOUR-BUCKET>替換為Bucket名稱。將<YOUR-ENDPOINT>替換為OSS Endpoint,例如oss-cn-hangzhou.aliyuncs.com。
              public string Host { get; set; } = "<YOUR-BUCKET>.<YOUR-ENDPOINT>";
              // 指定上傳到OSS的檔案首碼。
              public string UploadDir { get; set; } = "user-dir-prefix/";
              // 指定到期時間,單位為秒。
              public int ExpireTime { get; set; } = 3600;
              public class PolicyConfig
              {
                  public string expiration { get; set; }
                  public List<List<object>> conditions { get; set; }
              }
              public class PolicyToken
              {
                  public string Accessid { get; set; }
                  public string Policy { get; set; }
                  public string Signature { get; set; }
                  public string Dir { get; set; }
                  public string Host { get; set; }
                  public string Expire { get; set; }
              }
              public static void Main(string[] args)
              {
                  var builder = WebApplication.CreateBuilder(args);
                  var app = builder.Build();
      
                  builder.Logging.AddConsole();
                  var logger = builder.Services.BuildServiceProvider().GetRequiredService<ILogger<Program>>();
      
                  app.UseStaticFiles(); 
      
                  app.MapGet("/", async (context) =>
                  {
                      var filePath = Path.Combine(Directory.GetCurrentDirectory(), "templates/index.html");
                      var htmlContent = await File.ReadAllTextAsync(filePath);
                      await context.Response.WriteAsync(htmlContent);
                      logger.LogInformation("GET request to root path");
                  });
      
                  app.MapGet("/get_post_signature_for_oss_upload", async (context) =>
                  {
                      var program = new Program(logger);
                      var token = program.GetPolicyToken();
      
                      logger.LogInformation($"Token: {token}");
      
                      context.Response.ContentType = "application/json";
                      await context.Response.WriteAsync(token);
                  });
      
                  app.Run();
              }
      
              public Program(ILogger<Program> logger)
              {
                  _logger = logger;
              }
      
              private string ToUnixTime(DateTime dateTime)
              {
                  return ((DateTimeOffset)dateTime).ToUnixTimeSeconds().ToString();
              }
      
              private string GetPolicyToken()
              {
                  var expireDateTime = DateTime.Now.AddSeconds(ExpireTime);
                  var config = new PolicyConfig
                  {
                      expiration = FormatIso8601Date(expireDateTime),
                      conditions = new List<List<object>>()
                  };
                  config.conditions.Add(new List<object>
                  {
                      "content-length-range", 0, 1048576000
                  });
                  var policy = JsonConvert.SerializeObject(config);
                  var policyBase64 = EncodeBase64("utf-8", policy);
                  var signature = ComputeSignature(AccessKeySecret, policyBase64);
                  var policyToken = new PolicyToken
                  {
                      Accessid = AccessKeyId,
                      Host = Host,
                      Policy = policyBase64,
                      Signature = signature,
                      Expire = ToUnixTime(expireDateTime),
                      Dir = UploadDir
                  };
                  return JsonConvert.SerializeObject(policyToken);
              }
      
              private string FormatIso8601Date(DateTime dtime)
              {
                  return dtime.ToUniversalTime().ToString("yyyy-MM-dd'T'HH:mm:ss.fff'Z'",
                                          CultureInfo.CurrentCulture);
              }
      
              private string EncodeBase64(string codeType, string code)
              {
                  string encode = "";
                  byte[] bytes = Encoding.GetEncoding(codeType).GetBytes(code);
                  try
                  {
                      encode = Convert.ToBase64String(bytes);
                  }
                  catch
                  {
                      encode = code;
                  }
                  return encode;
              }
      
              private string ComputeSignature(string key, string data)
              {
                  using (var algorithm = new HMACSHA1(Encoding.UTF8.GetBytes(key)))
                  {
                      return Convert.ToBase64String(algorithm.ComputeHash(Encoding.UTF8.GetBytes(data)));
                  }
              }
          }
      }
      
  2. 用戶端使用Post簽名和Post Policy等資訊調用PostObject通過HTML表單的方式上傳檔案到OSS。

    以js為例:

    <!DOCTYPE html>
    <html lang="zh-CN">
    <head>
      <meta charset="UTF-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <title>上傳檔案到OSS</title>
    </head>
    <body>
      <div class="container">
        <form>
          <div class="mb-3">
            <label for="file" class="form-label">選擇檔案</label>
            <input type="file" class="form-control" id="file" name="file" required>
          </div>
          <button type="submit" class="btn btn-primary">上傳</button>
        </form>
      </div>
      <script type="text/javascript">
          const form = document.querySelector('form');
          const fileInput = document.querySelector('#file');
          form.addEventListener('submit', (event) => {
            event.preventDefault();
            let file = fileInput.files[0];
            let filename = fileInput.files[0].name;
            fetch('/get_post_signature_for_oss_upload', { method: 'GET' })
              .then(response => response.json())
              .then(data => {
                const formData = new FormData();
                formData.append('name',filename);
                formData.append('policy', data.policy);
                formData.append('OSSAccessKeyId', data.ossAccessKeyId);
                formData.append('success_action_status', '200');
                formData.append('signature', data.signature);
                formData.append('key', data.dir + filename);
                // file必須為最後一個表單域,除file以外的其他表單域無順序要求。
                formData.append('file', file);
                fetch(data.host, { method: 'POST', body: formData},).then((res) => {
                  console.log(res);
                  alert('檔案已上傳');
                });
              })
              .catch(error => {
                console.log('Error occurred while getting OSS upload parameters:', error);
              });
          });
      </script>
    </body>
    </html>
    

注意事項

資料安全

防止覆蓋同名Object

上傳時預設會覆蓋同名Object,您可以選擇以下任意方式防止Object被意外覆蓋。

  • 開啟版本控制功能

    開啟版本控制功能後,被覆蓋的Object會以歷史版本的形式儲存下來。您可以隨時恢複歷史版本Object。更多資訊,請參見版本控制介紹

  • 在上傳請求中攜帶禁止覆蓋同名Object的參數

    在上傳請求的表單域中攜帶參數x-oss-forbid-overwrite,並指定其值為true。當您上傳的Object在OSS中存在同名Object時,該Object會上傳失敗,並返回FileAlreadyExists錯誤。當不攜帶此參數或此參數的值為false時,同名Object會被覆蓋。

授權上傳

  • 為了防止第三方使用者未經授權在您的Bucket中上傳資料,OSS提供了Bucket和Object層級的存取權限控制。更多資訊,請參見存取控制

  • 使用簽名URL授權第三方使用者上傳指定檔案。簽名URL允許第三方使用者在沒有安全憑證或者授權的情況下進行上傳操作。第三方使用者使用簽名URL上傳檔案後,OSS將在指定的Bucket產生該檔案。使用預簽名URL上傳檔案

降低PUT類請求費用

如果要上傳的檔案數量較多,直接指定上傳的檔案類型為深度冷歸檔類型會造成較高的PUT類請求費用。建議您先將檔案的儲存類型指定為標準儲存進行上傳,然後通過生命週期規則將其轉儲為深度冷歸檔類型,從而降低PUT類請求費用。

避免影響OSS-HDFS服務

為避免影響OSS-HDFS服務的正常使用或者引發資料丟失的風險,在開通了OSS-HDFS服務的Bucket中,禁止以非OSS-HDFS服務提供的方式在OSS-HDFS的資料存放區目錄.dlsdata/中上傳Object。

上傳效能調優

如果您在上傳大量Object時,在命名上使用了順序首碼(如時間戳記或字母順序),可能會出現大量Object索引集中儲存於儲存空間中某個特定分區的情況,進而導致請求速率下降。建議您在上傳大量Object時,不要使用順序首碼的Object名稱,而是將順序首碼改為隨機性首碼。具體操作,請參見OSS效能最佳實務