C++中，使用libCurl实现http的post请求

#include"cJSON.h"
#include<iostream>
#include<string>
#include<QString>
#include "curl/curl.h"
using namespace std;

// 请求的服务器地址
const string CAL_HOST_URL = "http://127.0.0.1:31105";

size_t req_reply(void *ptr, size_t size, size_t nmemb, void *stream)
{
//    cout << "----->reply" << endl;
    string *str = (string*)stream;
//    cout << *str << endl;
    (*str).append((char*)ptr, size*nmemb);
    return size * nmemb;
}

// HTTP的POST请求方法
CURLcode CurlPostReq(const string &url, const string &postParams, string &response)
{
    // 初始化curl
    CURL *curl = curl_easy_init();
    // 返回code
    CURLcode res;
    if (curl)
    {
        // header信息设定
        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, "charsets: utf-8");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        // 参数信息设定
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str()); // url
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postParams.c_str()); // params
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, req_reply);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&response);
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, 3);
        // 发起请求
        res = curl_easy_perform(curl);
    }
    // 释放curl
    curl_easy_cleanup(curl);
    return res;
}

/*
 业务方法中的调用
*/
void post_dataCleansing() {
	// http请求初始化
	curl_global_init(CURL_GLOBAL_ALL);
	// 调用参数准备
	string postUrlStr = CAL_HOST_URL + "/data_cleansing";
	cJSON_AddItemToObject(paramRoot, "padding_value", cJSON_CreateNumber(1));
	cJSON_AddItemToObject(paramRoot, "resampling_rate", cJSON_CreateNumber(2));
	char *paramData = NULL;
	paramData = cJSON_PrintUnformatted(paramRoot);
	string postParams = paramData;
	// http请求调用
	string postResponseStr;
	auto res = CurlPostReq(postUrlStr, postParams, postResponseStr);
	if (res != CURLE_OK)
	    cout << "curl_easy_perform() failed: " + string(curl_easy_strerror(res)) << endl;
	else
	    cout << postResponseStr << endl;
	// http请求释放
	curl_global_cleanup();
}