使用curlpp发布和接收JSON有效负载

Question

对于curlpp C++包装器libcurl，如何为post请求指定JSON有效负载，以及如何作为响应接收JSON有效负载？从这里我该去哪里：

std::string json("{}");

std::list<std::string> header;
header.push_back("Content-Type: application/json");

cURLpp::Easy r;
r.setOpt(new curlpp::options::Url(url));
r.setOpt(new curlpp::options::HttpHeader(header));
// set payload from json?
r.perform();

然后，如何等待(JSON)响应并检索身体？

Answer 1

事实证明，这样做非常简单，即使是异步的：

std::future<std::string> invoke(std::string const& url, std::string const& body) {
  return std::async(std::launch::async,
    [](std::string const& url, std::string const& body) mutable {
      std::list<std::string> header;
      header.push_back("Content-Type: application/json");

      curlpp::Cleanup clean;
      curlpp::Easy r;
      r.setOpt(new curlpp::options::Url(url));
      r.setOpt(new curlpp::options::HttpHeader(header));
      r.setOpt(new curlpp::options::PostFields(body));
      r.setOpt(new curlpp::options::PostFieldSize(body.length()));

      std::ostringstream response;
      r.setOpt(new curlpp::options::WriteStream(&response));

      r.perform();

      return std::string(response.str());
    }, url, body);
}

Answer 2

通过分析文档，第五例展示了如何设置回调以获得响应：

// Set the writer callback to enable cURL to write result in a memory area
curlpp::types::WriteFunctionFunctor functor(WriteMemoryCallback);
curlpp::options::WriteFunction *test = new curlpp::options::WriteFunction(functor);
request.setOpt(test);

，其中回调被定义为

size_t WriteMemoryCallback(char* ptr, size_t size, size_t nmemb)

由于响应可以以块的形式到达，所以可以多次调用它。完成响应后，使用JSON图书馆解析它。