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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
下载对象
下载一个对象至本地

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://cloud.tencent.com/document/product/436/6224
.Build();

string secretId = "SECRET_ID"; // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.cloud.tencent.com/cam/capi
string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.cloud.tencent.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.cloud.tencent.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://cloud.tencent.com/document/product/436/6224
.Build();

string secretId = "SECRET_ID"; // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.cloud.tencent.com/cam/capi
string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.cloud.tencent.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.cloud.tencent.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。

示例代码六: 下载暂停、继续与取消

对于下载任务,可以通过以下方式暂停:
downloadTask.Pause();
暂停之后,可以通过以下方式续传:
downloadTask.Resume();
也通过以下方式取消上传:
downloadTask.Cancel();
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://cloud.tencent.com/document/product/436/6224
.Build();

string secretId = "SECRET_ID"; // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.cloud.tencent.com/cam/capi
string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.cloud.tencent.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.cloud.tencent.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://cloud.tencent.com/document/product/436/6224
.Build();

string secretId = "SECRET_ID"; // 云 API 密钥 SecretId, 获取 API 密钥请参照 https://console.cloud.tencent.com/cam/capi
string secretKey = "SECRET_KEY"; // 云 API 密钥 SecretKey, 获取 API 密钥请参照 https://console.cloud.tencent.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.cloud.tencent.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。