Object Storage Service:OSS SDK for Javaを使用してHTTP GETリクエストを許可する署名付きURLを生成する

使用上の注意

• このトピックでは、中国 (杭州) リージョンのパブリックエンドポイントを使用します。 OSSと同じリージョンにある他のAlibaba CloudサービスからOSSにアクセスする場合は、内部エンドポイントを使用します。 OSSリージョンとエンドポイントの詳細については、「リージョンとエンドポイント」をご参照ください。

• このトピックでは、アクセス資格情報は環境変数から取得します。 アクセス資格情報の設定方法の詳細については、「アクセス資格情報の設定」をご参照ください。

• このトピックでは、OSSエンドポイントを使用してOSSClientインスタンスを作成します。 カスタムドメイン名またはSecurity Token Service (STS) を使用してOSSClientインスタンスを作成する場合は、「OSSClientインスタンスの作成」をご参照ください。

• HTTP GETリクエストを許可する署名付きURLを生成するには、oss:GetObject権限が必要です。 詳細については、「RAMユーザーへのカスタムポリシーのアタッチ」をご参照ください。

  説明

  OSS SDK for Javaを使用して署名付きURLを生成する場合、SDKはローカルコンピューターに保存されているキー情報に基づいて特定のアルゴリズムを使用して署名を計算し、URLに署名を追加してURLの有効性とセキュリティを確保します。 署名を計算し、URLを構築するために実行される操作は、クライアント上で完了する。 ネットワーク経由でサーバーにリクエストを送信する必要はありません。 この方法では、OSS SDK for Javaを使用して署名付きURLを生成するための特定の権限を呼び出し元に付与する必要はありません。 ただし、サードパーティのユーザーが署名付きURLによって承認されたリソースに対して関連する操作を実行できるようにするには、API操作を呼び出して署名付きURLを生成する呼び出し元に対応する権限があることを確認する必要があります。

• このトピックでは、有効期間が7日間のV4署名付きURLを使用します。 詳細については、「URLにV4署名を含める (推奨) 」をご参照ください。

プロセス

次の図は、署名付きURLを使用してオブジェクトをダウンロードする方法を示しています。

サンプルコード

1. 次のサンプルコードは、HTTP GETリクエストを許可する署名付きURLを生成する方法の例を示しています。

   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 {
           // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. 
           String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
           // Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
           EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
           // Specify the name of the bucket. Example: examplebucket. 
           String bucketName = "examplebucket";
           // Specify the full path of the object. Example: exampleobject.txt. Do not include the bucket name in the full path of the object. 
           String objectName = "exampleobject.txt";
           // Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. 
           String region = "cn-hangzhou";
   
           // Create an OSSClient instance. 
           ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
           clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
           OSS ossClient = OSSClientBuilder.create()
                   .endpoint(endpoint)
                   .credentialsProvider(credentialsProvider)
                   .clientConfiguration(clientBuilderConfiguration)
                   .region(region)
                   .build();
   
           try {
               // Specify the validity period of the signed URL. Unit: milliseconds. In this example, the validity period is set to 1 hour. 
               Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
               // Generate a signed URL that allows HTTP GET requests. In this example, no additional request headers are specified. Other users can access the relevant content directly by using the 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. 次のサンプルコードは、HTTP GETリクエストがオブジェクトをダウンロードできるようにする署名付きURLの使用方法の例を示しています。

   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) {
           // Specify the signed URL that allows HTTP GET requests. 
           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**********";
           // Specify the path in which the downloaded object is stored, including the object 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");
   
           // Specify the response code.
           int responseCode = httpConn.getResponseCode();
           if (responseCode == HttpURLConnection.HTTP_OK) {
               // Configure the input stream.
               InputStream inputStream = new BufferedInputStream(httpConn.getInputStream());
               // Configure the output stream.
               FileOutputStream outputStream = new FileOutputStream(savePath);
   
               byte[] buffer=new byte[4096]; // Specify the size of the 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=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"; // Specify the name of the downloaded object.
   
   fetch(fileURL)
       .then(response => {
           if (!response.ok) {
               throw new Error(`Server replied HTTP code: ${response.status}`);
           }
           return response.blob(); // Change the type of the response to blob.
       })
       .then(blob => {
           const link = document.createElement('a');
           link.href = window.URL.createObjectURL(blob);
           link.download=savePath; // Specify the name of the downloaded object.
           document.body.appendChild(link); // This step ensures that the signed URL exists in the document.
           link.click(); // Click the signed URL to simulate the object download.
           link.remove(); // Remove the signed URL after the object is downloaded.
           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"; // Specify the path in which you want to store the downloaded object.
           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 {
           // Specify the signed URL and the path in which you want to store the object.
           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"; // Replace your_username with your username.
           
           // Create a URL object.
           NSURL *url = [NSURL URLWithString:fileURL];
           
           // Create an object download task.
           NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
               // Handle errors.
               if (error) {
                   NSLog(@"Error during download: %@", error.localizedDescription);
                   return;
               }
               
               // Check the data of the object.
               if (!data) {
                   NSLog(@"No data received.");
                   return;
               }
               
               // Save the object.
               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 object download task.
           [task resume];
           
           // Continue to run the main thread to complete the asynchronous request.
           [[NSRunLoop currentRunLoop] run];
       }
       return 0;
   }

その他のシナリオ

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 {
        // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. 
        String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
        // Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
		    // Specify the name of the bucket. Example: examplebucket. 
        String bucketName = "examplebucket";
        // Specify the full path of the object. Example: exampleobject.txt. Do not include the bucket name in the full path of the object. 
        String objectName = "exampleobject.txt";
        // Specify the version ID of the object. 
        String versionId = "CAEQARiBgID8rumR2hYiIGUyOTAyZGY2MzU5MjQ5ZjlhYzQzZjNlYTAyZDE3****";
        // Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. 
        String region = "cn-hangzhou";

        // Create an OSSClient instance. 
        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);
            // Specify the validity period of the signed URL. Unit: milliseconds. In this example, the validity period is set to 1 hour. 
            Date expiration = new Date(new Date().getTime() + 3600 * 1000L);
            generatePresignedUrlRequest.setExpiration(expiration);
            // Specify the version ID of the object. 
            Map<String, String> queryParam = new HashMap<String, String>();
            queryParam.put("versionId", versionId);
            generatePresignedUrlRequest.setQueryParameter(queryParam);
            // Generate the signed 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();
            }
        }
    }
}

関連ドキュメント

• 署名付きURLを使用してオブジェクトをダウンロードするために使用される完全なサンプルコードについては、GitHubをご覧ください。

• 署名付きURLを使用してオブジェクトをダウンロードするために呼び出すことができるAPI操作の詳細については、「GeneratePresignedUrlRequest」をご参照ください。