如何：連接至 HTTP 伺服器 (C++ REST SDK)
利用 C++ REST SDK (代號名稱 "Casablanca")，您可以更容易從 C++ 應用程式連接至 HTTP 伺服器。 這個頁面顯示三個範例。 第一個範例示範建立 HTTP GET 要求及接收回應的基本方式。 第二個範例與第一個範例相似，但會建置使用自訂標頭值的 HTTP 要求。 第三個範例示範如何使用 HTTP PUT 將檔案上傳至伺服器。
這些範例後面還有顯示 #include 和 using 陳述式的較完整範例。
警告
此主題包含 C++ REST SDK 1.0 (代號名稱 "Casablanca") 的相關資訊。如果您是使用 Codeplex Casablanca 網頁 提供的較新版本，則請使用位於 http://casablanca.codeplex.com/documentation 的本機說明文件。
建立 HTTP GET 要求及接收回應
以下是使用 web::http::client::http_client 類別來建立 HTTP GET 要求的方法。 web::http::client::http_response 類別代表伺服器的回應。 如需將 HTTP 回應處理成 JSON 資料的類似範例，請參閱<如何：使用 JSON 資料＞。
// Creates an HTTP request and prints the length of the response stream.
pplx::task<void> HTTPStreamingAsync()
{
http_client client(L"https://www.fourthcoffee.com");
// Make the request and asynchronously process the response.
return client.request(methods::GET).then([](http_response response)
{
// Print the status code.
std::wostringstream ss;
ss << L"Server returned returned status code " << response.status_code() << L'.' << std::endl;
std::wcout << ss.str();
// TODO: Perform actions here reading from the response stream.
auto bodyStream = response.body();
// In this example, we print the length of the response to the console.
ss.str(std::wstring());
ss << L"Content length is " << response.headers().content_length() << L" bytes." << std::endl;
std::wcout << ss.str();
});
/* Sample output:
Server returned returned status code 200.
Content length is 63803 bytes.
*/
}
建立使用自訂標頭值的 HTTP GET 要求
此範例類似上一個範例，但其使用 web::http::client::http_request 類別，以手動建立要求標頭。
// Builds an HTTP request that uses custom header values.
pplx::task<void> HTTPRequestCustomHeadersAsync()
{
http_client client(L"https://www.fourthcoffee.com");
// Manually build up an HTTP request with header and request URI.
http_request request(methods::GET);
request.headers().add(L"MyHeaderField", L"MyHeaderValue");
request.set_request_uri(L"requestpath");
return client.request(request).then([](http_response response)
{
// Print the status code.
std::wostringstream ss;
ss << L"Server returned returned status code " << response.status_code() << L"." << std::endl;
std::wcout << ss.str();
});
/* Sample output:
Server returned returned status code 200.
*/
}
使用 HTTP PUT 將檔案上傳至伺服器
此範例類似第一個範例，但其使用 concurrency::streams::file_stream 類別，以非同步方式從磁碟讀取檔案。 Concurrency::streams::basic_istream 物件會保存檔案內容。 此範例使用 web::http::methods::PUT，將作業指定為 HTTP PUT 作業。 如需使用資料流的更多範例，請參閱＜如何：使用非同步資料流＞。
// Upload a file to an HTTP server.
pplx::task<void> UploadFileToHttpServerAsync()
{
using concurrency::streams::file_stream;
using concurrency::streams::basic_istream;
// To run this example, you must have a file named myfile.txt in the current folder.
// Alternatively, you can use the following code to create a stream from a text string.
// std::string s("abcdefg");
// auto ss = concurrency::streams::stringstream::open_istream(s);
// Open stream to file.
return file_stream<unsigned char>::open_istream(L"myfile.txt").then([](pplx::task<basic_istream<unsigned char>> previousTask)
{
try
{
auto fileStream = previousTask.get();
// Make HTTP request with the file stream as the body.
http_client client(L"https://www.fourthcoffee.com");
return client.request(methods::PUT, L"myfile", fileStream).then([fileStream](pplx::task<http_response> previousTask)
{
fileStream.close();
std::wostringstream ss;
try
{
auto response = previousTask.get();
ss << L"Server returned returned status code " << response.status_code() << L"." << std::endl;
}
catch (const http_exception& e)
{
ss << e.what() << std::endl;
}
std::wcout << ss.str();
});
}
catch (const std::system_error& e)
{
std::wostringstream ss;
ss << e.what() << std::endl;
std::wcout << ss.str();
// Return an empty task.
return pplx::task_from_result();
}
});
/* Sample output:
The request must be resent
*/
}
完整範例
以下是完整的範例。
// basic-http-client.cpp
#include <http_client.h>
#include <filestream.h>
#include <iostream>
#include <sstream>
using namespace web::http;
using namespace web::http::client;
// Creates an HTTP request and prints the length of the response stream.
pplx::task<void> HTTPStreamingAsync()
{
http_client client(L"https://www.fourthcoffee.com");
// Make the request and asynchronously process the response.
return client.request(methods::GET).then([](http_response response)
{
// Print the status code.
std::wostringstream ss;
ss << L"Server returned returned status code " << response.status_code() << L'.' << std::endl;
std::wcout << ss.str();
// TODO: Perform actions here reading from the response stream.
auto bodyStream = response.body();
// In this example, we print the length of the response to the console.
ss.str(std::wstring());
ss << L"Content length is " << response.headers().content_length() << L" bytes." << std::endl;
std::wcout << ss.str();
});
/* Sample output:
Server returned returned status code 200.
Content length is 63803 bytes.
*/
}
// Builds an HTTP request that uses custom header values.
pplx::task<void> HTTPRequestCustomHeadersAsync()
{
http_client client(L"https://www.fourthcoffee.com");
// Manually build up an HTTP request with header and request URI.
http_request request(methods::GET);
request.headers().add(L"MyHeaderField", L"MyHeaderValue");
request.set_request_uri(L"requestpath");
return client.request(request).then([](http_response response)
{
// Print the status code.
std::wostringstream ss;
ss << L"Server returned returned status code " << response.status_code() << L"." << std::endl;
std::wcout << ss.str();
});
/* Sample output:
Server returned returned status code 200.
*/
}
// Upload a file to an HTTP server.
pplx::task<void> UploadFileToHttpServerAsync()
{
using concurrency::streams::file_stream;
using concurrency::streams::basic_istream;
// To run this example, you must have a file named myfile.txt in the current folder.
// Alternatively, you can use the following code to create a stream from a text string.
// std::string s("abcdefg");
// auto ss = concurrency::streams::stringstream::open_istream(s);
// Open stream to file.
return file_stream<unsigned char>::open_istream(L"myfile.txt").then([](pplx::task<basic_istream<unsigned char>> previousTask)
{
try
{
auto fileStream = previousTask.get();
// Make HTTP request with the file stream as the body.
http_client client(L"https://www.fourthcoffee.com");
return client.request(methods::PUT, L"myfile", fileStream).then([fileStream](pplx::task<http_response> previousTask)
{
fileStream.close();
std::wostringstream ss;
try
{
auto response = previousTask.get();
ss << L"Server returned returned status code " << response.status_code() << L"." << std::endl;
}
catch (const http_exception& e)
{
ss << e.what() << std::endl;
}
std::wcout << ss.str();
});
}
catch (const std::system_error& e)
{
std::wostringstream ss;
ss << e.what() << std::endl;
std::wcout << ss.str();
// Return an empty task.
return pplx::task_from_result();
}
});
/* Sample output:
The request must be resent
*/
}
int wmain()
{
// This example uses the task::wait method to ensure that async operations complete before the app exits.
// In most apps, you typically don�t wait for async operations to complete.
std::wcout << L"Calling HTTPStreamingAsync..." << std::endl;
HTTPStreamingAsync().wait();
std::wcout << L"Calling HTTPRequestCustomHeadersAsync..." << std::endl;
HTTPRequestCustomHeadersAsync().wait();
std::wcout << L"Calling UploadFileToHttpServerAsync..." << std::endl;
UploadFileToHttpServerAsync().wait();
}