注意事項

• 本文以華東1（杭州）外網(wǎng)Endpoint為例。如果您希望通過與OSS同地域的其他阿里云產(chǎn)品訪問OSS，請使用內(nèi)網(wǎng)Endpoint。關(guān)于OSS支持的Region與Endpoint的對應(yīng)關(guān)系，請參見OSS地域和訪問域名。

• 本文以從環(huán)境變量讀取訪問憑證為例。如何配置訪問憑證，請參見Java配置訪問憑證。

• 本文以OSS域名新建OSSClient為例。如果您希望通過自定義域名、STS等方式新建OSSClient，請參見新建OSSClient。

• 生成GET方法的簽名URL時，您必須具有oss:GetObject權(quán)限。具體操作，請參見為RAM用戶授權(quán)自定義的權(quán)限策略。

  說明

  生成簽名URL過程中，SDK利用本地存儲的密鑰信息，根據(jù)特定算法計算出簽名（signature），然后將其附加到URL上，以確保URL的有效性和安全性。這一系列計算和構(gòu)造URL的操作都是在客戶端完成，不涉及網(wǎng)絡(luò)請求到服務(wù)端。因此，生成簽名URL時不需要授予調(diào)用者特定權(quán)限。但是，為避免第三方用戶無法對簽名URL授權(quán)的資源執(zhí)行相關(guān)操作，需要確保調(diào)用生成簽名URL接口的身份主體被授予對應(yīng)的權(quán)限。

• 本文以V4簽名URL為例，有效期最大為7天。更多信息，請參見簽名版本4（推薦）。

使用過程

使用簽名URL下載文件的過程如下：

代碼示例

1. 文件擁有者生成GET方法的簽名URL。

   import com.aliyun.oss.*;
   import com.aliyun.oss.common.auth.*;
   import com.aliyun.oss.common.comm.SignVersion;
   
   import java.net.URL;
   import java.util.Date;
   
   public class Demo {
       public static void main(String[] args) throws Throwable {
           // 以華東1（杭州）的外網(wǎng)Endpoint為例，其它Region請按實際情況填寫。
           String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
           // 從環(huán)境變量中獲取訪問憑證。運行本代碼示例之前，請確保已設(shè)置環(huán)境變量OSS_ACCESS_KEY_ID和OSS_ACCESS_KEY_SECRET。
           EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
           // 填寫Bucket名稱，例如examplebucket。
           String bucketName = "examplebucket";
           // 填寫Object完整路徑，例如exampleobject.txt。Object完整路徑中不能包含Bucket名稱。
           String objectName = "exampleobject.txt";
           // 填寫Bucket所在地域。以華東1（杭州）為例，Region填寫為cn-hangzhou。
           String region = "cn-hangzhou";
   
           // 創(chuàng)建OSSClient實例。
           ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
           clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
           OSS ossClient = OSSClientBuilder.create()
                   .endpoint(endpoint)
                   .credentialsProvider(credentialsProvider)
                   .clientConfiguration(clientBuilderConfiguration)
                   .region(region)
                   .build();
   
           try {
               // 設(shè)置簽名URL過期時間，單位為毫秒。本示例以設(shè)置過期時間為1小時為例。
               Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
               // 生成以GET方法訪問的簽名URL。本示例沒有額外請求頭，其他人可以直接通過瀏覽器訪問相關(guān)內(nèi)容。
               URL url = ossClient.generatePresignedUrl(bucketName, objectName, expiration);
               System.out.println(url);
           } 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.");
               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();
               }
           }
       }
   }

2. 其他人使用GET方法的簽名URL下載文件。

   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) {
           // 替換為生成的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**********";
           // 填寫文件保存的目標(biāo)路徑，包括文件名和擴展名。
           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");
   
           // 檢查響應(yīng)代碼
           int responseCode = httpConn.getResponseCode();
           if (responseCode == HttpURLConnection.HTTP_OK) {
               // 輸入流
               InputStream inputStream = new BufferedInputStream(httpConn.getInputStream());
               // 輸出流
               FileOutputStream outputStream = new FileOutputStream(savePath);
   
               byte[] buffer = new byte[4096]; // 緩沖區(qū)
               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"; // 文件將在下載時使用的文件名
   
   fetch(fileURL)
       .then(response => {
           if (!response.ok) {
               throw new Error(`Server replied HTTP code: ${response.status}`);
           }
           return response.blob(); // 將響應(yīng)轉(zhuǎn)換為 blob
       })
       .then(blob => {
           const link = document.createElement('a');
           link.href = window.URL.createObjectURL(blob);
           link.download = savePath; // 設(shè)置下載文件的名字
           document.body.appendChild(link); // 此步驟確保鏈接存在于文檔中
           link.click(); // 模擬點擊下載鏈接
           link.remove(); // 完成后移除鏈接
           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 {
           // 定義文件 URL 和保存路徑（修改為有效的路徑）
           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?zhí)鎿Q為您的用戶名
           
           // 創(chuàng)建 URL 對象
           NSURL *url = [NSURL URLWithString:fileURL];
           
           // 創(chuàng)建下載任務(wù)
           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;
               }
               
               // 檢查數(shù)據(jù)
               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);
               }
           }];
           
           // 啟動任務(wù)
           [task resume];
           
           // 讓主線程繼續(xù)運行以便異步請求能夠完成
           [[NSRunLoop currentRunLoop] run];
       }
       return 0;
   }

其他場景

import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.model.GeneratePresignedUrlRequest;
import java.net.URL;
import java.util.*;
import java.util.Date;

public class Demo {
    public static void main(String[] args) throws Throwable {
        // 以華東1（杭州）的外網(wǎng)Endpoint為例，其它Region請按實際情況填寫。
        String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
        // 從環(huán)境變量中獲取訪問憑證。運行本代碼示例之前，請確保已設(shè)置環(huán)境變量OSS_ACCESS_KEY_ID和OSS_ACCESS_KEY_SECRET。
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
		    // 填寫B(tài)ucket名稱，例如examplebucket。
        String bucketName = "examplebucket";
        // 填寫Object完整路徑，例如exampleobject.txt。Object完整路徑中不能包含Bucket名稱。
        String objectName = "exampleobject.txt";
        // 填寫Object的versionId。
        String versionId = "CAEQARiBgID8rumR2hYiIGUyOTAyZGY2MzU5MjQ5ZjlhYzQzZjNlYTAyZDE3****";
        // 填寫B(tài)ucket所在地域。以華東1（杭州）為例，Region填寫為cn-hangzhou。
        String region = "cn-hangzhou";

        // 創(chuàng)建OSSClient實例。
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);        
        OSS ossClient = OSSClientBuilder.create()
        .endpoint(endpoint)
        .credentialsProvider(credentialsProvider)
        .clientConfiguration(clientBuilderConfiguration)
        .region(region)               
        .build();

        try {
            // 創(chuàng)建請求。
            GeneratePresignedUrlRequest generatePresignedUrlRequest = new GeneratePresignedUrlRequest(bucketName, objectName);
            // 設(shè)置HttpMethod為GET。
            generatePresignedUrlRequest.setMethod(HttpMethod.GET);
            // 設(shè)置簽名URL過期時間，單位為毫秒。本示例以設(shè)置過期時間為1小時為例。
            Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
            generatePresignedUrlRequest.setExpiration(expiration);
            // Object的versionId。
            Map<String, String> queryParam = new HashMap<String, String>();
            queryParam.put("versionId", versionId);
            generatePresignedUrlRequest.setQueryParameter(queryParam);
            // 生成簽名URL。
            URL url = ossClient.generatePresignedUrl(generatePresignedUrlRequest);
            System.out.println(url);
        } 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.");
            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();
            }
        }
    }
}

相關(guān)文檔

• 關(guān)于使用簽名URL下載文件的完整示例代碼，請參見GitHub示例。

• 關(guān)于使用簽名URL下載文件的API接口說明，請參見GeneratePresignedUrlRequest。