Object Storage Service:Télécharger un objet à l'aide d'une URL pré-signée (SDK Java V1)

Précautions

• Cette rubrique utilise le point de terminaison public de la région Chine (Hangzhou). Pour accéder à OSS depuis d'autres services Alibaba Cloud situés dans la même région, utilisez un point de terminaison interne. Pour plus de détails sur les régions et points de terminaison pris en charge, consultez Régions et points de terminaison.

• Dans cette rubrique, les identifiants d'accès sont obtenus à partir des variables d'environnement. Pour plus d'informations, consultez Configuration des identifiants d'accès.

• Cette rubrique illustre la création d'une instance OSSClient avec un point de terminaison OSS. Pour d'autres configurations, telles que l'utilisation d'un domaine personnalisé ou l'authentification via des identifiants du Security Token Service (STS), consultez Configuration du client.

• Aucune autorisation n'est nécessaire pour générer une URL pré-signée. Toutefois, pour qu'un tiers puisse télécharger l'objet via cette URL, l'utilisateur qui génère l'URL doit disposer de l'autorisation oss:GetObject. Pour savoir comment accorder des autorisations, consultez Accorder des autorisations personnalisées à un utilisateur RAM.

• Cette rubrique utilise les URL pré-signées V4 à titre d'exemple. La période de validité maximale est de sept jours. Pour plus d'informations, consultez Version 4 de la signature (recommandée).

Procédure

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

Exemples de code

1. Le propriétaire de l'objet génère une URL pré-signée pour une requête GET.

   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 {
           // This example uses the public endpoint of the China (Hangzhou) region. Specify the actual endpoint.
           String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
           // Obtain access credentials from environment variables. Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
           EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
           // Enter the bucket name. For example, examplebucket.
           String bucketName = "examplebucket";
           // Enter the full path of the object. For example, exampleobject.txt. The full path cannot contain the bucket name.
           String objectName = "exampleobject.txt";
           // Enter the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to cn-hangzhou.
           String region = "cn-hangzhou";
   
           // Create an OSSClient instance.
           // When the OSSClient instance is no longer used, call the shutdown method to release resources.
           ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
           clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
           OSS ossClient = OSSClientBuilder.create()
                   .endpoint(endpoint)
                   .credentialsProvider(credentialsProvider)
                   .clientConfiguration(clientBuilderConfiguration)
                   .region(region)
                   .build();
   
           try {
               // Set the expiration time of the presigned URL in milliseconds. This example sets the expiration time to one hour.
               Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
               // Generate a presigned URL for a GET request. This example does not include additional request headers. Other users can directly access the content through a browser.
               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. Les autres utilisateurs téléchargent l'objet à l'aide de l'URL pré-signée.

   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;
   }

Autres scénarios

import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.comm.SignVersion;
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 {
        // This example uses the public endpoint of the China (Hangzhou) region. Specify the actual endpoint.
        String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
        // Obtain access credentials from environment variables. Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
	// Enter the bucket name. For example, examplebucket.
        String bucketName = "examplebucket";
        // Enter the full path of the object. For example, exampleobject.txt. The full path cannot contain the bucket name.
        String objectName = "exampleobject.txt";
        // Enter the versionId of the object.
        String versionId = "CAEQARiBgID8rumR2hYiIGUyOTAyZGY2MzU5MjQ5ZjlhYzQzZjNlYTAyZDE3****";
        // Enter the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to cn-hangzhou.
        String region = "cn-hangzhou";

        // Create an OSSClient instance.
        // When the OSSClient instance is no longer used, call the shutdown method to release resources.
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);        
        OSS ossClient = OSSClientBuilder.create()
        .endpoint(endpoint)
        .credentialsProvider(credentialsProvider)
        .clientConfiguration(clientBuilderConfiguration)
        .region(region)               
        .build();

        try {
            // Create a request.
            GeneratePresignedUrlRequest generatePresignedUrlRequest = new GeneratePresignedUrlRequest(bucketName, objectName);
            // Set HttpMethod to GET.
            generatePresignedUrlRequest.setMethod(HttpMethod.GET);
            // Set the expiration time of the presigned URL in milliseconds. This example sets the expiration time to one hour.
            Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
            generatePresignedUrlRequest.setExpiration(expiration);
            // The versionId of the object.
            Map<String, String> queryParam = new HashMap<String, String>();
            queryParam.put("versionId", versionId);
            generatePresignedUrlRequest.setQueryParameter(queryParam);
            // Generate the presigned 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();
            }
        }
    }
}

import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.GeneratePresignedUrlRequest;

import java.net.URL;
import java.util.Date;

public class Demo {
    public static void main(String[] args) throws Throwable {
        // Set yourCustomEndpoint to your custom domain name. For example, http://static.example.com.
        String endpoint = "yourCustomEndpoint";
        // Enter the region information of your bucket, for example, cn-hangzhou.
        String region = "cn-hangzhou";
        // Enter the bucket name. For example, examplebucket.
        String bucketName = "examplebucket";
        // Enter the full path of the object. For example, exampleobject.txt. The full path cannot contain the bucket name.
        String objectName = "exampleobject.txt";

        // Obtain access credentials from environment variables. Before you run this code, configure the environment variables.
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();

        // Create an OSSClient instance.
        // When the OSSClient instance is no longer used, call the shutdown method to release resources.
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        // Note: Set this to true to enable the CNAME option.
        clientBuilderConfiguration.setSupportCname(true);
        // Explicitly declare the use of the V4 signature algorithm.
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
        OSS ossClient = OSSClientBuilder.create()
                .endpoint(endpoint)
                .credentialsProvider(credentialsProvider)
                .clientConfiguration(clientBuilderConfiguration)
                .region(region)
                .build();

        try {
            // Set the expiration time of the generated presigned URL in milliseconds. This example sets the expiration time to one hour.
            Date expiration = new Date(new Date().getTime() + 3600 * 1000L);

            // Generate a presigned URL.
            GeneratePresignedUrlRequest request = new GeneratePresignedUrlRequest(bucketName, objectName, HttpMethod.GET);

            // Set the expiration time.
            request.setExpiration(expiration);

            // Generate a presigned URL for an HTTP GET request.
            URL signedUrl = ossClient.generatePresignedUrl(request);
            // Print the presigned URL.
            System.out.println("signed url for getObject: " + signedUrl);
        } 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();
            }
        }
    }
}

import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.CredentialsProviderFactory;
import com.aliyun.oss.common.auth.EnvironmentVariableCredentialsProvider;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.GeneratePresignedUrlRequest;

import java.net.URL;
import java.net.URLEncoder;
import java.util.Date;

public class Demo {
    public static void main(String[] args) throws Throwable {
        // Enter your custom domain name. For example, http://static.example.com.
        String endpoint = "http://static.example.com";
        // Obtain access credentials from environment variables. Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();

        // Enter the bucket name. For example, examplebucket.
        String bucketName = "examplebucket";
        // Enter the full path of the object. For example, exampleobject.txt. The full path cannot contain the bucket name.
        String objectName = "exampleobject.txt";

        // Create an OSSClient instance.
        // When the OSSClient instance is no longer used, call the shutdown method to release resources.
        String region = "cn-hangzhou";
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        // Note: If you use a custom domain name, you must set CNAME to true.
        clientBuilderConfiguration.setSupportCname(true);

        //Set the V4 signature algorithm.
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
        OSS ossClient = OSSClientBuilder.create()
                .endpoint(endpoint)
                .credentialsProvider(credentialsProvider)
                .clientConfiguration(clientBuilderConfiguration)
                .region(region)
                .build();

        URL signedUrl = null;
        try {
            // Set the expiration time of the generated presigned URL in milliseconds. This example sets the expiration time to one hour.
            Date expiration = new Date(new Date().getTime() + 3600 * 1000L);

            // Define the file name to be displayed on the client during download. This example uses "homework.txt".
            String filename = "homework.txt";

            // Generate a presigned URL.
            GeneratePresignedUrlRequest request = new GeneratePresignedUrlRequest(bucketName, objectName, HttpMethod.GET);

            // Set the download behavior (force download instead of preview) and the file name.
            request.getResponseHeaders().setContentDisposition("attachment;filename=" + URLEncoder.encode(filename,"UTF-8"));

            // Set the expiration time.
            request.setExpiration(expiration);

            // Generate a presigned URL for an HTTP GET request.
            signedUrl = ossClient.generatePresignedUrl(request);
            // Print the presigned URL.
            System.out.println("signed url for getObject: " + signedUrl);
        } 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());
        }
    }

}

Références

• Pour obtenir l'exemple de code complet relatif au téléchargement d'un objet à l'aide d'une URL pré-signée, consultez l'exemple GitHub.

• Pour plus d'informations sur l'opération API utilisée pour générer une URL pré-signée, consultez GeneratePresignedUrlRequest.