默认情况下，OSS Bucket中的文件是私有的，仅文件拥有者可访问。您可以使用Go SDK生成带有过期时间的GET方法签名URL，以允许他人临时下载文件。在有效期内可多次访问，超期后需重新生成。
注意事项
本文以华东1（杭州）外网Endpoint为例。如果您希望通过与OSS同地域的其他阿里云产品访问OSS，请使用内网Endpoint。关于OSS支持的Region与Endpoint的对应关系，请参见OSS地域和访问域名。
本文以从环境变量读取访问凭证为例。如何配置访问凭证，请参见配置访问凭证。
本文以OSS域名新建OSSClient为例。如果您希望通过自定义域名、STS等方式新建OSSClient，请参见新建OSSClient。
生成GET方法的签名URL时，您必须具有
oss:GetObject权限。具体操作，请参见为RAM用户授权自定义的权限策略。说明生成签名URL过程中，SDK利用本地存储的密钥信息，根据特定算法计算出签名（signature），然后将其附加到URL上，以确保URL的有效性和安全性。这一系列计算和构造URL的操作都是在客户端完成，不涉及网络请求到服务端。因此，生成签名URL时不需要授予调用者特定权限。但是，为避免第三方用户无法对签名URL授权的资源执行相关操作，需要确保调用生成签名URL接口的身份主体被授予对应的权限。
本文以V4签名URL为例，有效期最大为7天。更多信息，请参见签名版本4（推荐）。
使用过程
使用签名URL下载文件的过程如下：
示例代码
文件拥有者生成GET方法的签名URL。
package main import ( "log" "github.com/aliyun/aliyun-oss-go-sdk/oss" ) func main() { // 从环境变量中获取访问凭证。运行本代码示例之前，请确保已设置环境变量OSS_ACCESS_KEY_ID和OSS_ACCESS_KEY_SECRET。 provider, err := oss.NewEnvironmentVariableCredentialsProvider() if err != nil { log.Printf("Error: %v\n", err) } // 创建OSSClient实例。 // yourEndpoint填写Bucket对应的Endpoint，以华东1（杭州）为例，填写为https://oss-cn-hangzhou.aliyuncs.com。其它Region请按实际情况填写。 // yourRegion填写Bucket所在地域，以华东1（杭州）为例，填写为cn-hangzhou。其它Region请按实际情况填写。 clientOptions := []oss.ClientOption{oss.SetCredentialsProvider(&provider)} clientOptions = append(clientOptions, oss.Region("cn-hangzhou")) // 设置签名版本 clientOptions = append(clientOptions, oss.AuthVersion(oss.AuthV4)) client, err := oss.New("yourEndpoint", "", "", clientOptions...) if err != nil { log.Printf("Error: %v\n", err) } // 填写Bucket名称，例如examplebucket。 bucketName := "examplebucket" // 填写文件名称，例如exampleobject.txt。文件名称中不能包含Bucket名称。 objectName := "exampleobject.txt" // 将Object下载到本地文件，并保存到指定的本地路径中。如果指定的本地文件存在会覆盖，不存在则新建。 bucket, err := client.Bucket(bucketName) if err != nil { log.Printf("Error: %v\n", err) } // 生成用于下载的签名URL，并指定签名URL的有效时间为600秒。 signedURL, err := bucket.SignURL(objectName, oss.HTTPGet, 600) if err != nil { log.Printf("Error: %v\n", err) } log.Printf("Sign Url:%s\n", signedURL) }其他人使用GET方法的签名URL下载文件。
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) { // 替换为生成的GET方法的签名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**********"; // 填写文件保存的目标路径，包括文件名和扩展名。 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"); // 检查响应代码 int responseCode = httpConn.getResponseCode(); if (responseCode == HttpURLConnection.HTTP_OK) { // 输入流 InputStream inputStream = new BufferedInputStream(httpConn.getInputStream()); // 输出流 FileOutputStream outputStream = new FileOutputStream(savePath); byte[] buffer = new byte[4096]; // 缓冲区 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"; // 文件将在下载时使用的文件名 fetch(fileURL) .then(response => { if (!response.ok) { throw new Error(`Server replied HTTP code: ${response.status}`); } return response.blob(); // 将响应转换为 blob }) .then(blob => { const link = document.createElement('a'); link.href = window.URL.createObjectURL(blob); link.download = savePath; // 设置下载文件的名字 document.body.appendChild(link); // 此步骤确保链接存在于文档中 link.click(); // 模拟点击下载链接 link.remove(); // 完成后移除链接 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"; // 修改后的保存路径 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 { // 定义文件 URL 和保存路径（修改为有效的路径） 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"; // 请替换为您的用户名 // 创建 URL 对象 NSURL *url = [NSURL URLWithString:fileURL]; // 创建下载任务 NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { // 错误处理 if (error) { NSLog(@"Error during download: %@", error.localizedDescription); return; } // 检查数据 if (!data) { NSLog(@"No data received."); return; } // 保存文件 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); } }]; // 启动任务 [task resume]; // 让主线程继续运行以便异步请求能够完成 [[NSRunLoop currentRunLoop] run]; } return 0; }