Object Storage Service:Télécharger un objet à l'aide d'une URL pré-signée (SDK Go V2)

Notes

• Le code exemple de cette rubrique utilise l'ID de région cn-hangzhou pour la région Chine (Hangzhou). Par défaut, un endpoint public est utilisé pour accéder aux ressources du compartiment. Si vous accédez aux ressources du compartiment depuis d'autres services Alibaba Cloud situés dans la même région, utilisez un endpoint interne. Pour plus d'informations sur les régions et les endpoints OSS, consultez la page Regions and endpoints.

• Dans cette rubrique, les identifiants d'accès sont récupérés à partir des variables d'environnement. Pour savoir comment configurer les identifiants d'accès, consultez la section Configure access credentials.

• Aucune autorisation n'est requise pour générer une URL pré-signée. Toutefois, pour qu'un tiers puisse télécharger l'objet à l'aide de cette URL, l'utilisateur qui la génère doit disposer de l'autorisation oss:GetObject . Pour plus d'informations sur l'attribution des autorisations, consultez la page Grant custom permissions to a RAM user.

• Cette rubrique utilise des URL pré-signées V4. La durée de validité maximale de ces URL est de sept jours. Pour plus d'informations, consultez la section (Recommended) Include a V4 signature in a URL.

Procédure

La procédure suivante décrit comment télécharger un objet à l'aide d'une URL pré-signée :

Définition de la méthode

Appelez une opération spécifique pour générer une URL pré-signée accordant des autorisations d'accès temporaires aux objets d'un compartiment. L'URL pré-signée peut être utilisée plusieurs fois avant son expiration.

Le code suivant présente la syntaxe de l'opération presign :

func (c *Client) Presign(ctx context.Context, request any, optFns ...func(*PresignOptions)) (result *PresignResult, err error)

Paramètres de requête

Le tableau suivant décrit les options de PresignOptions.

Paramètres de réponse

Le tableau suivant décrit les paramètres de réponse de PresignResult.

Exemple de code

1. L'exemple de code suivant montre comment un propriétaire d'objet peut générer une URL pré-signée autorisant les requêtes HTTP GET :

   package main
   
   import (
   	"context"
   	"flag"
   	"log"
   	"time"
   
   	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
   	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
   )
   
   // Define global variables.
   var (
   	region     string // The region in which the bucket is located.
   	bucketName string // The name of the bucket.
   	objectName string // The name of the object.
   )
   
   // The init function is used to initialize command-line parameters.
   func init() {
   	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
   	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
   	flag.StringVar(&objectName, "object", "", "The name of the object.")
   }
   
   func main() {
   	// Parse command-line parameters.
   	flag.Parse()
   
   	// Check whether the bucket name is empty.
   	if len(bucketName) == 0 {
   		flag.PrintDefaults()
   		log.Fatalf("invalid parameters, bucket name required")
   	}
   
   	// Check whether the region is empty.
   	if len(region) == 0 {
   		flag.PrintDefaults()
   		log.Fatalf("invalid parameters, region required")
   	}
   
   	// Check whether the object name is empty.
   	if len(objectName) == 0 {
   		flag.PrintDefaults()
   		log.Fatalf("invalid parameters, object name required")
   	}
   
   	// Load the default configurations and specify the credential provider and region.
   	cfg := oss.LoadDefaultConfig().
   		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
   		WithRegion(region)
   
   	// Create an OSS client.
   	client := oss.NewClient(cfg)
   
   	// Generate a presigned URL for the GetObject request.
   	result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
   		Bucket: oss.Ptr(bucketName),
   		Key:    oss.Ptr(objectName),
   	},
   		oss.PresignExpires(10*time.Minute),
   	)
   	if err != nil {
   		log.Fatalf("failed to get object presign %v", err)
   	}
   
   	log.Printf("request method:%v\n", result.Method)
   	log.Printf("request expiration:%v\n", result.Expiration)
   	log.Printf("request url:%v\n", result.URL)
   	if len(result.SignedHeaders) > 0 {
   		// If the returned result contains signed headers, you must include the corresponding request headers when you send a GET request using the presigned URL. Otherwise, the request may fail or a signature error may occur.
   		log.Printf("signed headers:\n")
   		for k, v := range result.SignedHeaders {
   			log.Printf("%v: %v\n", k, v)
   		}
   	}
   }
   

2. Les autres utilisateurs peuvent télécharger le fichier à l'aide de l'URL pré-signée pour les requêtes GET.

   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) {
           // Replace with the generated presigned URL for the GET request.
           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******************************************************";
           // Enter the destination path to save the file, including the file name and extension.
           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");
   
           // Check the response code.
           int responseCode = httpConn.getResponseCode();
           if (responseCode == HttpURLConnection.HTTP_OK) {
               // Input stream.
               InputStream inputStream = new BufferedInputStream(httpConn.getInputStream());
               // Output stream.
               FileOutputStream outputStream = new FileOutputStream(savePath);
   
               byte[] buffer = new byte[4096]; // Buffer.
               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"; // The file name to use for the download.
   
   fetch(fileURL)
       .then(response => {
           if (!response.ok) {
               throw new Error(`Server replied HTTP code: ${response.status}`);
           }
           return response.blob(); // Convert the response to a blob.
       })
       .then(blob => {
           const link = document.createElement('a');
           link.href = window.URL.createObjectURL(blob);
           link.download = savePath; // Set the name of the downloaded file.
           document.body.appendChild(link); // This step ensures that the link exists in the document.
           link.click(); // Simulate a click on the download link.
           link.remove(); // Remove the link after completion.
           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"; // The modified save path.
           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 {
           // Define the file URL and save path (change to a valid path).
           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"; // Replace with your username.
           
           // Create a URL object.
           NSURL *url = [NSURL URLWithString:fileURL];
           
           // Create a download task.
           NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
               // Error handling.
               if (error) {
                   NSLog(@"Error during download: %@", error.localizedDescription);
                   return;
               }
               
               // Check the data.
               if (!data) {
                   NSLog(@"No data received.");
                   return;
               }
               
               // Save the file.
               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);
               }
           }];
           
           // Start the task.
           [task resume];
           
           // Keep the main thread running so that the asynchronous request can be completed.
           [[NSRunLoop currentRunLoop] run];
       }
       return 0;
   }

Scénarios courants

package main

import (
	"context"
	"flag"
	"log"
	"time"

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

// Define global variables.
var (
	region     string // The region in which the bucket is located.
	bucketName string // The name of the bucket.
	objectName string // The name of the object.
)

// The init function is used to initialize command-line parameters.
func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

func main() {
	// Parse command-line parameters.
	flag.Parse()

	// Check whether the bucket name is empty.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}

	// Check whether the region is empty.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}

	// Check whether the object name is empty.
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Load the default configurations and specify the credential provider and region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	// Create an OSS client.
	client := oss.NewClient(cfg)

	// Generate a presigned URL for the GetObject request.
	result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
		Bucket:    oss.Ptr(bucketName),
		Key:       oss.Ptr(objectName),
		VersionId: oss.Ptr("yourVersionId"), // Specify the version ID.
	},
		oss.PresignExpires(10*time.Minute),
	)
	if err != nil {
		log.Fatalf("failed to get object presign %v", err)
	}
	log.Printf("get object presign result: %#v\n", result)
	log.Printf("get object url: %#v\n", result.URL)
}

package main

import (
	"context"
	"flag"
	"log"
	"time"

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

// Define global variables.
var (
	region     string // The region in which the bucket is located.
	bucketName string // The name of the bucket.
	objectName string // The name of the object.
)

// The init function is used to initialize command-line parameters.
func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

func main() {
	// Parse command-line parameters.
	flag.Parse()

	// Check whether the bucket name is empty.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}

	// Check whether the region is empty.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}

	// Check whether the object name is empty.
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Load the default configurations and specify the credential provider and region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region).
		WithEndpoint("http://static.example.com").
		WithUseCName(true)

	// Create an OSS client.
	client := oss.NewClient(cfg)

	// Generate a presigned URL for the GetObject request.
	result, err := client.Presign(context.TODO(), &oss.GetObjectRequest{
		Bucket: oss.Ptr(bucketName),
		Key:    oss.Ptr(objectName),
		//RequestPayer: oss.Ptr("requester"), // Specify the identity of the requester.
	},
		oss.PresignExpires(10*time.Minute),
	)
	if err != nil {
		log.Fatalf("failed to get object presign %v", err)
	}

	log.Printf("request method:%v\n", result.Method)
	log.Printf("request expiration:%v\n", result.Expiration)
	log.Printf("request url:%v\n", result.URL)
	if len(result.SignedHeaders) > 0 {
		// If you specify request headers when you generate a presigned URL that allows HTTP GET requests, make sure that the request headers are included in the GET request initiated using the presigned URL. This prevents request failures and signature errors.
		log.Printf("signed headers:\n")
		for k, v := range result.SignedHeaders {
			log.Printf("%v: %v\n", k, v)
		}
	}
}

Références

• Pour consulter l'exemple de code complet utilisé pour télécharger un objet à l'aide d'une URL pré-signée, rendez-vous sur la page GitHub example.

• Pour plus d'informations sur l'opération API permettant de télécharger un objet via une URL pré-signée, consultez la documentation Presign.