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 Java SDK產生帶有到期時間的GET方法簽名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Java配置訪問憑證。
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,請參見建立OSSClient。
產生GET方法的簽名URL時,您必須具有
oss:GetObject
許可權。具體操作,請參見為RAM使用者授權自訂的權限原則。說明產生簽名URL過程中,SDK利用本機存放區的密鑰資訊,根據特定演算法計算出簽名(signature),然後將其附加到URL上,以確保URL的有效性和安全性。這一系列計算和構造URL的操作都是在用戶端完成,不涉及網路請求到服務端。因此,產生簽名URL時不需要授予調用者特定許可權。但是,為避免第三方使用者無法對簽名URL授權的資源執行相關操作,需要確保調用產生簽名URL介面的身份主體被授予對應的許可權。
本文以V4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)。
通過以下樣本產生的簽名URL中如果包含特殊符號
+
,可能出現無法正常訪問該簽名URL的現象。如需正常訪問該簽名URL,請將簽名URL中的+
替換為%2B
。如果需要產生HTTPS協議的簽名URL,請將Endpoint中的通訊協定設定為HTTPS。
使用過程
使用簽名URL下載檔案的過程如下:
程式碼範例
檔案擁有者產生GET方法的簽名URL。
<?php if (is_file(__DIR__ . '/../autoload.php')) { require_once __DIR__ . '/../autoload.php'; } if (is_file(__DIR__ . '/../vendor/autoload.php')) { require_once __DIR__ . '/../vendor/autoload.php'; } use OSS\OssClient; use OSS\Core\OssException; use OSS\Http\RequestCore; use OSS\Http\ResponseCore; // 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。 $accessKeyId = getenv("OSS_ACCESS_KEY_ID"); $accessKeySecret = getenv("OSS_ACCESS_KEY_SECRET"); // yourEndpoint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 = "yourEndpoint"; // 填寫Bucket名稱。 $bucket= "examplebucket"; // 填寫不包含Bucket名稱在內的Object完整路徑。 $object = "exampleobject.txt"; // 指定簽名URL的到期時間為600s(最長可達32400s)。 $timeout = 600; // 產生預覽的簽名URL,然後使用Bucket綁定的自訂網域名進行訪問。 $options= array( "response-content-disposition"=>"inline",); // 產生下載的簽名URL。 /*$options = array( "response-content-disposition"=>"attachment", );*/ try { $ossClient = new OssClient($accessKeyId, $accessKeySecret, $endpoint, false); $signedUrl = $ossClient->signUrl($bucket, $object, $timeout,'GET',$options); } catch (OssException $e) { printf(__FUNCTION__ . ": FAILED\n"); printf($e->getMessage() . "\n"); return; } print(__FUNCTION__ . ": signedUrl: " . $signedUrl . "\n");
其他人使用GET方法的簽名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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********"
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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********"; // 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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********"; 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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********" 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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********" 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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********"; 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=LTAI5************/20241112/cn-hangzhou/oss/aliyun_v4_request&x-oss-signature=ed5a939feb8d79a389572719f7e2939939936d0**********"; 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; }
其他情境
產生帶versionId的簽名URL
相關文檔
關於使用簽名URL下載檔案的API介面說明,請參見GeneratePresignedUrlRequest。