如何使用方法 POST 使用 curlpp 上传文件和 json 数据

Question

我想使用 curlpp 库编写 C++ 代码，如果可能的话，它在 curl 上的工作方式与以下示例完全相同。

> curl -H "Content-Type: application/json" -X POST -d '{"param1":"val1", "param2":"val2", "param3":"val3"}' --data-binary '@/tmp/somefolder/file.bin' https://my-api.somedomain.com:1024/my_command_url
>

我能够使用方法 POST 编写传输 json 文本，但是当我添加上传命令时，这个库用 PUT 代替了 POST。

Answer 1

我决定post在这里回答，也许它会对像我这样的人有所帮助

static string post_request(const string url,const string body1,const string path2file)
{
   const string field_divider="&";
   stringstream result;
   try
   {
      using namespace std;

      // This block responsible for reading in the fastest way media file
      //      and prepare it for sending on API server
      ifstream is(path2file);
      is.seekg(0, ios_base::end);
      size_t size=is.tellg();
      is.seekg(0, ios_base::beg);
      vector<char> v(size/sizeof(char));
      is.read((char*) &v[0], size);
      is.close();
      string body2(v.begin(),v.end());

      // Initialization
      curlpp::Cleanup cleaner;
      curlpp::Easy request;
      list< string > headers;
      headers.push_back("Content-Type: application/json");
      headers.push_back("User-Agent: curl/7.77.7");

      using namespace curlpp::Options;

      request.setOpt(new Verbose(true));
      request.setOpt(new HttpHeader(headers));
      request.setOpt(new Url(url));
      request.setOpt(new PostFields(body1+field_divider+body2));
      request.setOpt(new PostFieldSize(body1.length()+field_divider.length()+body2.length()));
      request.setOpt(new curlpp::options::SslEngineDefault());
      request.setOpt(WriteStream(&result));
      request.perform();
   }
   catch ( curlpp::LogicError & e )
     {
       cout << e.what() << endl;
     }
   catch ( curlpp::RuntimeError & e )
     {
       cout << e.what() << endl;
     }

   return (result.str());

}

Answer 2

我尝试使用发布的答案，但发现它不能很好地与 express' json 解析器一起使用，并且每次都会给出错误的请求。我认为使用 curlpp 的表单数据很可能是最佳选择。有关发送 json 字符串和格式文件的基本示例，请参见下面的代码：

std::string BasicFormDataPost(std::string url, std::string body1, std::string filename)
{
  std::ostringstream result;
  try
  {
  // Initialization
  curlpp::Cleanup cleaner;
  curlpp::Easy request;
  curlpp::Forms formParts;
  formParts.push_back(new curlpp::FormParts::Content("formjson",body1)); // One has to remember to JSON.parse on the server to use the body data.
  formParts.push_back(new curlpp::FormParts::File("attachment", filename));

  using namespace curlpp::Options;

  // request.setOpt(new Verbose(true));
  request.setOpt(new Url(url));
  request.setOpt(new HttpPost(formParts));
  request.setOpt(WriteStream(&result));
  request.perform();
  return std::string( result.str());  
 }
 catch ( curlpp::LogicError & e )
 {
   std::cout << e.what() << std::endl;
 }
 catch ( curlpp::RuntimeError & e )
 {
   std::cout << e.what() << std::endl;
 }

}

这个答案是从之前的答案和位于以下位置的 curlpp 示例拼凑而成的：https://github.com/datacratic/curlpp/tree/master/examples

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