如何使用curlpp通过POST方法上传文件和json数据

How to upload file and json data with method POST use curlpp

本文关键字：文件 json 数据 方法 何使用 curlpp 通过 POST      更新时间：2023-10-16

我想使用curlpp库编写C++代码，当然，如果可能的话，它的工作方式与下面的curl示例完全一样。

> 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
>

我可以用POST方法编写transfer-json文本，但当我添加upload命令时，这个库代替了PUT而不是POST。

我决定在这里发布答案，也许这会帮助像我这样的人

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());
}

我尝试使用发布的答案，但发现它不能很好地与express的json解析器配合使用，每次都会发出错误的请求。我认为使用curlpp的表单数据可能是最好的选择。有关发送json字符串和格式为的文件的基本示例，请参阅下面的代码

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;
}
}

这个答案是根据上一个答案和curlpp示例拼凑而成的，这些示例位于：https://github.com/datacratic/curlpp/tree/master/examples

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