預設情況下，OSS Bucket中的檔案是私人的，僅檔案擁有者可訪問。您可以使用OSS Python SDK產生帶有到期時間的GET方法預簽名URL，以允許他人臨時下載檔案。在有效期間內可多次訪問，超期後需重建。
注意事項
本文以華東1（杭州）外網Endpoint為例。如果您希望通過與OSS同地區的其他阿里雲產品訪問OSS，請使用內網Endpoint。關於OSS支援的Region與Endpoint的對應關係，請參見OSS地區和訪問網域名稱。
本文以從環境變數讀取存取憑證為例。如何配置訪問憑證，請參見配置訪問
本文以OSS網域名稱建立OSSClient為例。如果您希望通過自訂網域名、STS等方式建立OSSClient，請參見初始化（Python SDK V1）。
預簽名URL無需許可權即可產生，但僅當您擁有
oss:GetObject許可權時，第三方才能通過該預簽名URL成功下載檔案。具體授權操作，請參見為RAM使用者授權自訂的權限原則。本文以V4預簽名URL為例，有效期間最大為7天。更多資訊，請參見簽名版本4（推薦）。
使用過程
使用預簽名URL下載檔案的過程如下：
範例程式碼
檔案擁有者產生GET方法的預簽名URL。
# -*- coding: utf-8 -*- import oss2 from oss2.credentials import EnvironmentVariableCredentialsProvider # 從環境變數中擷取訪問憑證。運行本程式碼範例之前，請確保已設定環境變數OSS_ACCESS_KEY_ID和OSS_ACCESS_KEY_SECRET。 auth = oss2.ProviderAuthV4(EnvironmentVariableCredentialsProvider()) # 填寫Bucket所在地區對應的Endpoint。以華東1（杭州）為例，Endpoint填寫為https://oss-cn-hangzhou.aliyuncs.com。 endpoint = "https://oss-cn-hangzhou.aliyuncs.com" # 填寫Endpoint對應的Region資訊，例如cn-hangzhou。注意，v4簽名下，必須填寫該參數 region = "cn-hangzhou" # yourBucketName填寫儲存空間名稱。 bucket = oss2.Bucket(auth, endpoint, "yourBucketName", region=region) # 填寫Object完整路徑，例如exampledir/exampleobject.txt。Object完整路徑中不能包含Bucket名稱。 object_name = 'exampledir/exampleobject.txt' # 產生下載檔案的預簽名URL，有效時間為600秒。 # 產生預簽名URL時，OSS預設會對Object完整路徑中的正斜線（/）進行轉義，從而導致產生的簽名URL無法直接使用。 # 設定slash_safe為True，OSS不會對Object完整路徑中的正斜線（/）進行轉義，此時產生的簽名URL可以直接使用。 url = bucket.sign_url('GET', object_name, 600, slash_safe=True) print('預簽名URL的地址為：', url)其他人使用GET方法的預簽名URL下載檔案。
curl
curl -SO "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"Java
import java.io.BufferedInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; public class Demo { public static void main(String[] args) { // 替換為產生的GET方法的預簽名URL。 String fileURL = "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"; // 填寫檔案儲存的目標路徑，包括檔案名稱和副檔名。 String savePath = "C:/downloads/myfile.txt"; try { downloadFile(fileURL, savePath); System.out.println("Download completed!"); } catch (IOException e) { System.err.println("Error during download: " + e.getMessage()); } } private static void downloadFile(String fileURL, String savePath) throws IOException { URL url = new URL(fileURL); HttpURLConnection httpConn = (HttpURLConnection) url.openConnection(); httpConn.setRequestMethod("GET"); // 檢查響應代碼 int responseCode = httpConn.getResponseCode(); if (responseCode == HttpURLConnection.HTTP_OK) { // 輸入資料流 InputStream inputStream = new BufferedInputStream(httpConn.getInputStream()); // 輸出資料流 FileOutputStream outputStream = new FileOutputStream(savePath); byte[] buffer = new byte[4096]; // 緩衝區 int bytesRead; while ((bytesRead = inputStream.read(buffer)) != -1) { outputStream.write(buffer, 0, bytesRead); } outputStream.close(); inputStream.close(); } else { System.out.println("No file to download. Server replied HTTP code: " + responseCode); } httpConn.disconnect(); } }Node.js
const https = require('https'); const fs = require('fs'); const fileURL = "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"; const savePath = "C:/downloads/myfile.txt"; https.get(fileURL, (response) => { if (response.statusCode === 200) { const fileStream = fs.createWriteStream(savePath); response.pipe(fileStream); fileStream.on('finish', () => { fileStream.close(); console.log("Download completed!"); }); } else { console.error(`Download failed. Server responded with code: ${response.statusCode}`); } }).on('error', (err) => { console.error("Error during download:", err.message); });Python
import requests file_url = "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************" save_path = "C:/downloads/myfile.txt" try: response = requests.get(file_url, stream=True) if response.status_code == 200: with open(save_path, 'wb') as f: for chunk in response.iter_content(4096): f.write(chunk) print("Download completed!") else: print(f"No file to download. Server replied HTTP code: {response.status_code}") except Exception as e: print("Error during download:", e)Go
package main import ( "io" "net/http" "os" ) func main() { fileURL := "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************" savePath := "C:/downloads/myfile.txt" response, err := http.Get(fileURL) if err != nil { panic(err) } defer response.Body.Close() if response.StatusCode == http.StatusOK { outFile, err := os.Create(savePath) if err != nil { panic(err) } defer outFile.Close() _, err = io.Copy(outFile, response.Body) if err != nil { panic(err) } println("Download completed!") } else { println("No file to download. Server replied HTTP code:", response.StatusCode) } }JavaScript
const fileURL = "https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"; const savePath = "C:/downloads/myfile.txt"; // 檔案將在下載時使用的檔案名稱 fetch(fileURL) .then(response => { if (!response.ok) { throw new Error(`Server replied HTTP code: ${response.status}`); } return response.blob(); // 將響應轉換為 blob }) .then(blob => { const link = document.createElement('a'); link.href = window.URL.createObjectURL(blob); link.download = savePath; // 設定下載檔案的名字 document.body.appendChild(link); // 此步驟確保連結存在於文檔中 link.click(); // 類比點擊下載連結 link.remove(); // 完成後移除連結 console.log("Download completed!"); }) .catch(error => { console.error("Error during download:", error); });Android-Java
import android.os.AsyncTask; import android.os.Environment; import java.io.BufferedInputStream; import java.io.FileOutputStream; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; public class DownloadTask extends AsyncTask<String, String, String> { @Override protected String doInBackground(String... params) { String fileURL = params[0]; String savePath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/myfile.txt"; // 修改後的儲存路徑 try { URL url = new URL(fileURL); HttpURLConnection httpConn = (HttpURLConnection) url.openConnection(); httpConn.setRequestMethod("GET"); int responseCode = httpConn.getResponseCode(); if (responseCode == HttpURLConnection.HTTP_OK) { InputStream inputStream = new BufferedInputStream(httpConn.getInputStream()); FileOutputStream outputStream = new FileOutputStream(savePath); byte[] buffer = new byte[4096]; int bytesRead; while ((bytesRead = inputStream.read(buffer)) != -1) { outputStream.write(buffer, 0, bytesRead); } outputStream.close(); inputStream.close(); return "Download completed!"; } else { return "No file to download. Server replied HTTP code: " + responseCode; } } catch (Exception e) { return "Error during download: " + e.getMessage(); } } }Objective-C
#import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { @autoreleasepool { // 定義檔案 URL 和儲存路徑（修改為有效路徑） NSString *fileURL = @"https://examplebucket.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T092756Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a******************************************************"; NSString *savePath = @"/Users/your_username/Desktop/myfile.txt"; // 請替換為您的使用者名稱 // 建立 URL 對象 NSURL *url = [NSURL URLWithString:fileURL]; // 建立下載任務 NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { // 錯誤處理 if (error) { NSLog(@"Error during download: %@", error.localizedDescription); return; } // 檢查資料 if (!data) { NSLog(@"No data received."); return; } // 儲存檔案 NSError *writeError = nil; BOOL success = [data writeToURL:[NSURL fileURLWithPath:savePath] options:NSDataWritingAtomic error:&writeError]; if (success) { NSLog(@"Download completed!"); } else { NSLog(@"Error saving file: %@", writeError.localizedDescription); } }]; // 啟動任務 [task resume]; // 讓主線程繼續運行以便非同步請求能夠完成 [[NSRunLoop currentRunLoop] run]; } return 0; }