dotNet Core APIでS3ファイル(apk)をダウンロードする

AWS S3ライブラリーを使って、AWS S3のバケットからAPKファイルをダウンロードしたのでメモしておく。

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Mime;
using System.Threading.Tasks;
using Amazon;
using Amazon.S3;
using Amazon.S3.Model;
using Microsoft.AspNetCore.Mvc;

namespace WebApi.Controllers
{
 [ApiController]
 [Route("api/[controller]")]
 // [Route("[controller]")]
 public class S3Controller : ControllerBase
 {
 private const string bucketName = "hoge";
 // private const string keyName = "hoge.jpg";
 private const string keyName = "HelloWorld.apk";
 // Specify your bucket region (an example region is shown).
 private static readonly RegionEndpoint bucketRegion = RegionEndpoint.USEast2;
 private static IAmazonS3 client;

// APKをダウンロード
 [HttpGet("apk")]
 public async Task<IActionResult> GetApkFileAsync()
 {
 client = new AmazonS3Client(bucketRegion);
 //string res = await ReadObjectDataAsync();
 //System.Net.Mime.MediaTypeNames.Image newImage = System.Net.Mime.MediaTypeNames.Image.FromFile("SampImag.jpg");
 //return File(file, System.Net.Mime.MediaTypeNames.Image.Jpeg, "sample.jpg");
 // return Ok();

 Stream apkStream = await ReadObjectDataAsync2();

 Response.Headers.Add("Content-Disposition", new ContentDisposition
 {
 FileName = "HelloWorld.apk",
 Inline = true // false = prompt the user for downloading; true = browser to try to show the file inline
 }.ToString());

 return File(apkStream, "application/octet-stream");
 }

 public async Task<Stream> ReadObjectDataAsync2()
 {
 try
 {
 GetObjectRequest request = new GetObjectRequest
 {
 BucketName = bucketName,
 Key = keyName
 };

 using (var getObjectResponse = await client.GetObjectAsync(request))
 {
 using (var responseStream = getObjectResponse.ResponseStream)
 {
 var stream = new MemoryStream();
 await responseStream.CopyToAsync(stream);
 stream.Position = 0;
 return stream;
 }
 }
 }
 catch (Exception exception)
 {
 throw new Exception("Read object operation failed.", exception);
 }
 }

 private static async Task<string> ReadObjectDataAsync()
 {
 string responseBody = "";
 try
 {
 GetObjectRequest request = new GetObjectRequest
 {
 BucketName = bucketName,
 Key = keyName
 };
 using (GetObjectResponse response = await client.GetObjectAsync(request))
 using (Stream responseStream = response.ResponseStream)
 using (StreamReader reader = new StreamReader(responseStream))
 {
 string title = response.Metadata["x-amz-meta-title"]; // Assume you have "title" as medata added to the object.
 string contentType = response.Headers["Content-Type"];
 Console.WriteLine("Object metadata, Title: {0}", title);
 Console.WriteLine("Content type: {0}", contentType);

 responseBody = reader.ReadToEnd(); // Now you process the response body.
 //file = System.Text.Encoding.ASCII.GetBytes(responseBody);
 //file = System.Drawing.ImageConverter

 }
 return responseBody;
 }
 catch (AmazonS3Exception e)
 {
 // If bucket or object does not exist
 Console.WriteLine("Error encountered ***. Message:'{0}' when reading object", e.Message);
 throw e;
 }
 catch (Exception e)
 {
 Console.WriteLine("Unknown encountered on server. Message:'{0}' when reading object", e.Message);
 throw e;
 }
 }

// JPGをダウンロード
 [HttpGet("image")]
 public async Task<IActionResult> GetImageFileAsync()
 {
 client = new AmazonS3Client(bucketRegion);
 //string res = await ReadObjectDataAsync();
 //System.Net.Mime.MediaTypeNames.Image newImage = System.Net.Mime.MediaTypeNames.Image.FromFile("SampImag.jpg");
 //return File(file, System.Net.Mime.MediaTypeNames.Image.Jpeg, "sample.jpg");
 // return Ok();

 

 Stream imageStream = await ReadObjectDataJPG();

 Response.Headers.Add("Content-Disposition", new ContentDisposition
 {
 FileName = "Image.jpg",
 Inline = true // false = prompt the user for downloading; true = browser to try to show the file inline
 }.ToString());

 return File(imageStream, "image/jpeg");
 }
 public async Task<Stream> ReadObjectDataJPG()
 {
 try
 {
 GetObjectRequest request = new GetObjectRequest
 {
 BucketName = bucketName,
 Key = keyName
 };

 using (var getObjectResponse = await client.GetObjectAsync(request))
 {
 using (var responseStream = getObjectResponse.ResponseStream)
 {
 var stream = new MemoryStream();
 await responseStream.CopyToAsync(stream);
 stream.Position = 0;
 return stream;
 }
 }
 }
 catch (Exception exception)
 {
 throw new Exception("Read object operation failed.", exception);
 }
 }


 [HttpGet]
 public int GetTest()
 {
 int aa = 0;
 return aa;
 }
 }
 
}

参考：

• Amazon Simple Storage Service endpoints and quotas
• MS開発者ガイドAWS SDK for .NET を使用したオブジェクトの取得
• Get an object Using the AWS SDK for .NET
• チュートリアル: ASP.NET Core で Web API を作成する
• C# MVC/API - Return an image from Amazon S3 for my API Call

→JPGのダウンロード

• HTTP Headers for File Downloads