node.js download using presigned url - Object Storage Service: Central de Documentação do Alibaba Cloud

Por padrão, os objetos em um bucket do Object Storage Service (OSS) são privados e apenas o proprietário do objeto pode acessá-los. Use o SDK do OSS para Node.js para gerar uma URL pré-assinada para uma requisição GET. Essa URL permite que outros usuários baixem o objeto temporariamente. É possível acessar a URL várias vezes antes da expiração. Após a expiração, gere uma nova URL.

Observações

Este tópico utiliza o endpoint público da região China (Hangzhou). Para acessar o OSS a partir de outros serviços da Alibaba Cloud na mesma região, use um endpoint interno. Para obter detalhes sobre as regiões e os endpoints compatíveis, consulte Regions and endpoints.
Este tópico apresenta um exemplo de como obter credenciais de acesso de variáveis de ambiente. Para mais informações sobre como configurar credenciais de acesso, consulte Configure access credentials (Node.js SDK).
Para gerar uma URL pré-assinada para uma requisição GET, é necessário ter a permissão oss:GetObject. Para mais informações, consulte Grant custom permissions to a RAM user.
O exemplo deste tópico utiliza URLs pré-assinadas V4. O período máximo de validade é de sete dias. Para mais informações, consulte Signature V4 (Recommended).

Processo

O processo para baixar um objeto usando uma URL pré-assinada é o seguinte:

Exemplos de código

O proprietário do objeto gera uma URL pré-assinada para uma requisição GET.

const OSS = require("ali-oss");

// Define a function to generate a presigned URL.
async function generateSignatureUrl(fileName) {
  // Obtain the presigned URL.
  const client = await new OSS({
      // 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.
      accessKeyId: process.env.OSS_ACCESS_KEY_ID,
      accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET,
      bucket: 'examplebucket',
      // Replace yourregion with the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to oss-cn-hangzhou.
      region: 'oss-cn-hangzhou',
      // Set secure to true to use HTTPS. This prevents the browser from blocking the generated download link.
      secure: true,
      authorizationV4: true
  });

  return await client.signatureUrlV4('GET', 3600, {
      headers: {} // Set the request headers based on the actual request headers.
  }, fileName);
}
// Call the function and pass the file name.
generateSignatureUrl('yourFileName').then(url => {
  console.log('Generated Signature URL:', url);
}).catch(err => {
  console.error('Error generating signature URL:', err);
});

Outros usuários baixam o objeto usando a URL pré-assinada para a requisição 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;
}

Outros cenários

Gerar uma URL pré-assinada com parâmetros de processamento de imagem

const OSS = require("ali-oss");

// Define a function to generate a presigned URL.
async function generateSignatureUrl(fileName) {
  // Obtain the presigned URL.
  const client = await new OSS({
    // 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.
    accessKeyId: process.env.OSS_ACCESS_KEY_ID,
    accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET,
    bucket: 'examplebucket',
    // Replace yourregion with the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to oss-cn-hangzhou.
    region: 'oss-cn-hangzhou',
    authorizationV4: true,
    cname: true
  });

  // Generate a signed URL that includes document processing parameters.
  return await client.signatureUrlV4('GET', 3600, {
    headers: {}, // Set the request headers based on the actual request headers.
    queries: {
     "x-oss-process": "image/resize,m_fixed,w_100,h_100" // Add image processing parameters.
    }
  }, fileName);
}

// Call the function and pass the image name.
generateSignatureUrl('test.jpg').then(url => {
  console.log('Generated Signature URL:', url);
}).catch(err => {
  console.error('Error generating signature URL:', err);
});

Gerar uma URL pré-assinada com um ID de versão

const OSS = require("ali-oss");

const client = await new OSS({
  // 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.
  accessKeyId: process.env.OSS_ACCESS_KEY_ID,
  accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET,
  bucket: 'examplebucket',
  // Replace yourregion with the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to oss-cn-hangzhou.
  region: 'oss-cn-hangzhou',
  // Set secure to true to use HTTPS. This prevents the browser from blocking the generated download link.
  secure: true,
  authorizationV4: true
});

// Generate a presigned URL.
const signedUrl = await client.signatureUrlV4('GET', 3600, {
  queries:{
    // Specify the version ID of the object.
    "versionId":'yourVersionId'
  }
}, 'demo.pdf');

Gerar uma URL pré-assinada para download usando um nome de domínio personalizado

O código a seguir apresenta um exemplo de como gerar uma URL pré-assinada para uma requisição GET com um nome de domínio personalizado.

const OSS = require("ali-oss");

// Define a function to generate a presigned URL.
async function generateSignatureUrl(fileName) {
  // Obtain the presigned URL.
  const client = await new OSS({
      // Use a custom domain name as the endpoint.
      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.
      accessKeyId: process.env.OSS_ACCESS_KEY_ID,
      accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET,
      bucket: 'examplebucket',
      // Replace yourregion with the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Region to oss-cn-hangzhou.
      region: 'oss-cn-hangzhou',
      authorizationV4: true,
      cname: true
  });

  return await client.signatureUrlV4('GET', 3600, {
      headers: {} // Set the request headers based on the actual request headers.
  }, fileName);
}
// Call the function and pass the file name.
generateSignatureUrl('yourFileName').then(url => {
  console.log('Generated Signature URL:', url);
}).catch(err => {
  console.error('Error generating signature URL:', err);
});

Referências

Para mais informações sobre a operação de API usada para gerar uma URL pré-assinada, consulte GeneratePresignedUrlRequest.