Como conectar a servidores HTTP (C++ REST SDK)

Com o C++ REST SDK (codinome "Casablanca"), você pode conectar com mais facilidade aos servidores HTTP do seu aplicativo C++. Esta página mostra três exemplos. O primeiro mostra uma maneira básica de criar uma solicitação HTTP GET e receber a resposta. O segundo exemplo é semelhante ao primeiro, mas compila uma solicitação HTTP que usa os valores de cabeçalho personalizados. O terceiro exemplo mostra como usar HTTP PUT para carregar um arquivo em um servidor.

Um exemplo mais completo que mostra as instruções #include e using é apresentado nesses exemplos.

Aviso

Este tópico contém informações para o C++ REST SDK 1.0 (codinome "Casablanca").Se você estiver usando uma versão mais recente da página da Web do Codeplex Casablanca, use então a documentação local em http://casablanca.codeplex.com/documentation.

Para criar uma solicitação HTTP GET e receber a resposta

Veja como usar a classe web::http::client::http_client para criar uma solicitação HTTP GET. A classe web::http::client::http_response representa a resposta do servidor. Para obter um exemplo semelhante que processa a resposta HTTP como dados JSON, consulte Como: trabalhar com dados JSON.

// Creates an HTTP request and prints the length of the response stream.
pplx::task<void> HTTPStreamingAsync()
{
    http_client client(L"http://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.
    */
}

Para criar uma solicitação HTTP GET que usa valores de cabeçalho personalizados

Este exemplo é semelhante ao anterior, mas usa a classe web::http::client::http_request para compilar manualmente os cabeçalhos da solicitação.

// Builds an HTTP request that uses custom header values.
pplx::task<void> HTTPRequestCustomHeadersAsync()
{
    http_client client(L"http://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.
    */
}

Para usar HTTP PUT para carregar um arquivo em um servidor

Este exemplo é semelhante ao primeiro, mas usa a classe concurrency::streams::file_stream para ler de forma assíncrona um arquivo do disco. O objeto concurrency::streams::basic_istream mantém o conteúdo do arquivo. Este exemplo usa o web::http::methods::PUT para especificar a operação como uma operação HTTP PUT. Para ver mais exemplos que usam fluxos, consulte Como: trabalhar com fluxos assíncronos.

// 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"http://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
    */
}

Exemplo completo

Veja o exemplo completo.

// 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"http://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"http://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"http://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();
}

Consulte também

Outros recursos

C++ REST SDK (codinome "Casablanca")