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下载对象

最后更新时间:2022-03-21 14:13:47

    简介

    本文档提供关于下载对象的 API 概览以及 SDK 示例代码。

    API 操作名 操作描述
    GET Object 下载对象 下载一个对象至本地

    SDK API 参考

    SDK 所有接口的具体参数与方法说明,请参考 SDK API

    高级接口(推荐)

    下载对象(断点续传)

    高级接口支持暂停、恢复以及取消下载请求,同时支持断点下载功能。

    说明:

    • .NET Framework 4.0 及以下的用户,高级接口暂不可用,详见 向下兼容指南
    • 高级下载接口从 5.4.26 版本开始支持并发分块下载,下载新版 SDK 前往 Releases 或参见 快速入门

    示例代码一: 下载对象

    using COSXML.Model.Object;
    using COSXML.Auth;
    using COSXML.Transfer;
    using System;
    using COSXML;
    using System.Threading.Tasks;
    namespace COSSnippet
    {
      public class TransferDownloadObjectModel {
         private CosXml cosXml;
         TransferDownloadObjectModel() {
          CosXmlConfig config = new CosXmlConfig.Builder()
            .SetRegion("COS_REGION") // 设置默认的地域, COS 地域的简称请参照 https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1
            .Build();
          
          string secretId = "SECRET_ID";   // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          long durationSecond = 600;          //每次请求签名有效时长,单位为秒
          QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
            secretKey, durationSecond);
          
          this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
        }
         /// 高级接口下载对象
        public async Task TransferDownloadObject()
        {
          // 初始化 TransferConfig
          TransferConfig transferConfig = new TransferConfig();
          // 手动设置高级下载接口的分块阈值为 20MB(默认为20MB), 从5.4.26版本开始支持!
          //transferConfig.DivisionForDownload = 20 * 1024 * 1024;
          // 手动设置高级下载接口的分块大小为 10MB(默认为5MB),不建议此处设置过小的分块值,可能导致频繁重试或下载速度不合预期
          //transferConfig.SliceSizeForDownload = 10 * 1024 * 1024;
          
          // 初始化 TransferManager
          TransferManager transferManager = new TransferManager(cosXml, transferConfig);
          
          String bucket = "examplebucket-1250000000"; //存储桶,格式:BucketName-APPID
          String cosPath = "exampleobject"; //对象在存储桶中的位置标识符,即称对象键
          string localDir = System.IO.Path.GetTempPath();//本地文件夹
          string localFileName = "my-local-temp-file"; //指定本地保存的文件名
          
          // 下载对象
          COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, cosPath, 
            localDir, localFileName);
            // 手动设置高级下载接口的并发数 (默认为5), 从5.4.26版本开始支持!
          //downloadTask.SetMaxTasks(10);
          downloadTask.progressCallback = delegate (long completed, long total)
          {
              Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
          };
           try {
            COSXML.Transfer.COSXMLDownloadTask.DownloadTaskResult result = await 
              transferManager.DownloadAsync(downloadTask);
            Console.WriteLine(result.GetResultInfo());
            string eTag = result.eTag;
          }
          catch (COSXML.CosException.CosClientException clientEx)
          {
            //请求失败
            Console.WriteLine("CosClientException: " + clientEx);
          }
          catch (COSXML.CosException.CosServerException serverEx)
          {
            //请求失败
            Console.WriteLine("CosServerException: " + serverEx.GetInfo());
          }
        }
          static void Main(string[] args)
        {
          TransferDownloadObjectModel m = new TransferDownloadObjectModel();
           /// 高级接口下载对象
          m.TransferDownloadObject().Wait();
        }
      }
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    示例代码二: 设置下载支持断点续传

    COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(request);
    //开启断点续传,当本地存在未下载完成文件时,追加下载到文件末尾
    //本地文件已存在部分不符合本次下载的内容,可能导致下载失败,请删除文件重试
    downloadTask.SetResumableDownload(true);
    try {
     COSXML.Transfer.COSXMLDownloadTask.DownloadTaskResult result = await 
     transferManager.DownloadAsync(downloadTask);
     Console.WriteLine(result.GetResultInfo());
     string eTag = result.eTag;
    } catch (Exception e) {
     Console.WriteLine("CosException: " + e);
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    示例代码三: 批量下载

    TransferConfig transferConfig = new TransferConfig();
    // 初始化 TransferManager
    TransferManager transferManager = new TransferManager(cosXml, transferConfig);
    // 存储桶名称,此处填入格式必须为 bucketname-APPID, 其中 APPID 获取参考 https://console.tencentcloud.com/developer
    string bucket = "examplebucket-1250000000";
    string localDir = System.IO.Path.GetTempPath();//本地文件夹
    for (int i = 0; i < 5; i++) {
    // 下载对象
    string cosPath = "exampleobject" + i; //对象在存储桶中的位置标识符,即称对象键
    string localFileName = "my-local-temp-file"; //指定本地保存的文件名
    COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, cosPath, 
      localDir, localFileName);
    await transferManager.DownloadAsync(downloadTask);
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    示例代码四:单链接限速下载

    TransferConfig transferConfig = new TransferConfig();
    // 初始化 TransferManager
    TransferManager transferManager = new TransferManager(cosXml, transferConfig);
    String bucket = "examplebucket-1250000000"; //存储桶,格式:BucketName-APPID
    String cosPath = "exampleobject"; //对象在存储桶中的位置标识符,即称对象键
    string localDir = System.IO.Path.GetTempPath();//本地文件夹
    string localFileName = "my-local-temp-file"; //指定本地保存的文件名
           
    GetObjectRequest request = new GetObjectRequest(bucket, 
           cosPath, localDir, localFileName);
    request.LimitTraffic(8 * 1000 * 1024); // 限制为1MB/s
    COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(request);
    await transferManager.DownloadAsync(downloadTask);
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    示例代码五:文件夹下载

    using COSXML.Common;
    using COSXML.CosException;
    using COSXML.Model;
    using COSXML.Model.Object;
    using COSXML.Model.Tag;
    using COSXML.Model.Bucket;
    using COSXML.Model.Service;
    using COSXML.Utils;
    using COSXML.Auth;
    using COSXML.Transfer;
    using System;
    using COSXML;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;
    using System.Reflection;
    using System.Text;
    using System.Threading;
    using System.Threading.Tasks;
    namespace COSSnippet
    {
     public class TransferDownloadObjectModel {
        private CosXml cosXml;
       private string nextMarker;
        TransferDownloadObjectModel() {
         CosXmlConfig config = new CosXmlConfig.Builder()
           .SetRegion("COS_REGION") // 设置默认的地域, COS 地域的简称请参照 https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1
           .Build();
           
         string secretId = "SECRET_ID";   // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
         string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
         long durationSecond = 600; //每次请求签名有效时长,单位为秒
         QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
           secretKey, durationSecond);
           
         this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
     }
        public void GetObjectsFromFolder()
    {
       // 注意:COS中实际不存在文件夹下载的接口
       // 需要通过组合 “指定前缀列出” 和 “遍历列出的对象key做下载” 两种操作,实现类似文件夹下载的操作
       // 下面的操作,把对象列出到列表里,然后异步下载列表中的对象
        String nextMarker = null;
       
        List<string>  downloadList = new List<string>();
        string bucket = "examplebucket-1250000000";
        string prefix = "folder1/"; //指定前缀
        // 循环请求直到没有下一页数据
        do
        {
            // 存储桶名称,此处填入格式必须为 bucketname-APPID, 其中 APPID 获取参考 https://console.tencentcloud.com/developer
            GetBucketRequest listRequest = new GetBucketRequest(bucket);
            //获取 folder1/ 下的所有对象以及子目录
            listRequest.SetPrefix(prefix);
            listRequest.SetMarker(nextMarker);
            //执行列出对象请求
            GetBucketResult listResult = cosXml.GetBucket(listRequest);
            ListBucket info = listResult.listBucket;
            // 对象列表
            List<ListBucket.Contents> objects = info.contentsList;
            // 下一页的下标
            nextMarker = info.nextMarker;
            
            //对象列表
            foreach (var content in objects)
            {
            downloadList.Add(content.key);
            Console.WriteLine("adding key:" + content.key);
            }
      } while (nextMarker != null);
        Console.WriteLine("download list construct done, " + downloadList.Count + " objects added");
            TransferConfig transferConfig = new TransferConfig();
        TransferManager transferManager = new TransferManager(cosXml, transferConfig);
        string localDir = System.IO.Path.GetTempPath();//本地文件夹
      
        List<Task> taskList = new List<Task>();
        for (int i = 0; i < downloadList.Count; i++)
        {
            // 遍历待下载列表,下载内容写到 filename_i 文件中
            COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, downloadList[i], 
                localDir, "filename_" + i.ToString());
            // 异步下载, 加入task队列
            Task task = transferManager.DownloadAsync(downloadTask);
            taskList.Add(task); 
        }
        Console.WriteLine("download tasks submitted, total " + taskList.Count + " tasks added");
        
        //等待TaskList中所有Task结束
        foreach(Task task in taskList)
        {
            task.Wait();
            Console.WriteLine("download completed");
        }
     }
          static void Main(string[] args)
         {
           TransferDownloadObjectModel m = new TransferDownloadObjectModel();
           /// 批量下载文件夹中文件
           m.GetObjectsFromFolder();
         }
       }
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    简单操作

    下载对象

    功能说明

    下载一个 Object(文件/对象)至本地(GET Object)。

    示例代码一:单对象简单下载

    using COSXML.Model.Object;
    using COSXML.Auth;
    using System;
    using COSXML;
    namespace COSSnippet
    {
      public class GetObjectModel {
         private CosXml cosXml;
         GetObjectModel() {
          CosXmlConfig config = new CosXmlConfig.Builder()
            .SetRegion("COS_REGION") // 设置默认的地域, COS 地域的简称请参照 https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1 
            .Build();
          
          string secretId = "SECRET_ID";   // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          long durationSecond = 600;          //每次请求签名有效时长,单位为秒
          QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
            secretKey, durationSecond);
          
          this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
        }
         /// 下载对象
        public void GetObject()
        {
          //.cssg-snippet-body-start:[get-object]
          try
          {
            // 存储桶名称,此处填入格式必须为 bucketname-APPID, 其中 APPID 获取参考 https://console.tencentcloud.com/developer
            string bucket = "examplebucket-1250000000";
            string key = "exampleobject"; //对象键
            string localDir = System.IO.Path.GetTempPath();//本地文件夹
            string localFileName = "my-local-temp-file"; //指定本地保存的文件名
            GetObjectRequest request = new GetObjectRequest(bucket, key, localDir, localFileName);
            //设置进度回调
            request.SetCosProgressCallback(delegate (long completed, long total)
            {
              Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
            });
            //执行请求
            GetObjectResult result = cosXml.GetObject(request);
            //请求成功
            Console.WriteLine(result.GetResultInfo());
          }
          catch (COSXML.CosException.CosClientException clientEx)
          {
            //请求失败
            Console.WriteLine("CosClientException: " + clientEx);
          }
          catch (COSXML.CosException.CosServerException serverEx)
          {
            //请求失败
            Console.WriteLine("CosServerException: " + serverEx.GetInfo());
          }
        }
         static void Main(string[] args)
        {
          GetObjectModel m = new GetObjectModel();
          /// 下载对象
          m.GetObject();
        }
      }
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

    示例代码二:下载对象到内存中

    using COSXML.Model.Object;
    using COSXML.Auth;
    using System;
    using COSXML;
    namespace COSSnippet
    {
      public class GetObjectModel {
         private CosXml cosXml;
         GetObjectModel() {
          CosXmlConfig config = new CosXmlConfig.Builder()
            .SetRegion("COS_REGION") // 设置默认的地域, COS 地域的简称请参照 https://www.tencentcloud.com/document/product/436/6224?from_cn_redirect=1 
            .Build();
          
          string secretId = "SECRET_ID";   // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.tencentcloud.com/cam/capi
          long durationSecond = 600;          //每次请求签名有效时长,单位为秒
          QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
            secretKey, durationSecond);
          
          this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
        }
         /// 下载返回 bytes 数据
        public void downloadToMem() {
          try
          {
            // 存储桶名称,此处填入格式必须为 bucketname-APPID, 其中 APPID 获取参考 https://console.tencentcloud.com/developer
            string bucket = "examplebucket-1250000000";
            string key = "exampleobject"; //对象键
          
            GetObjectBytesRequest request = new GetObjectBytesRequest(bucket, key);
            //设置进度回调
            request.SetCosProgressCallback(delegate (long completed, long total)
            {
              Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
            });
            //执行请求
            GetObjectBytesResult result = cosXml.GetObject(request);
            //获取内容到 byte 数组中
            byte[] content = result.content;
            //请求成功
            Console.WriteLine(result.GetResultInfo());
          }
          catch (COSXML.CosException.CosClientException clientEx)
          {
            //请求失败
            Console.WriteLine("CosClientException: " + clientEx);
          }
          catch (COSXML.CosException.CosServerException serverEx)
          {
            //请求失败
            Console.WriteLine("CosServerException: " + serverEx.GetInfo());
          }
        }
         // .cssg-methods-pragma
         static void Main(string[] args)
        {
          GetObjectModel m = new GetObjectModel();
           /// 下载对象到内存中
          m.downloadToMem();
          // .cssg-methods-pragma
        }
      }
    }
    
    说明:

    更多完整示例,请前往 GitHub 查看。

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