使用libCurl和JsonCpp从https webserver解析 [英] Using libCurl and JsonCpp to parse from https webserver
问题描述
所以我一直在互联网上查找一个使用libcurl和jsoncpp解析JSON的基本示例，但我还没有找到一个。
有人请给我正确的方向或在这里指定，一个简单的例子使用libcurl和jsoncpp，从指定的网页下载json（链接本身以.json结尾，所以它将直接拉json）解析和打印。 / p>
感谢您的帮助。非常感谢！
Euden
a）HTTP GET一个JSON对象通过libcurl然后b）解析它与JsonCpp。 @WhozCraig是正确的说，这是两个完全独立的活动，但我碰巧有一个项目，这两个所以我聚合这个小样本，从 如果你把这段代码放在一个名为
main.cpp
g ++ main.cpp -ljsoncpp -lcurl -o example.out&& ./example.out
// main.cpp
#include< cstdint> ;
#include< iostream>
#include< memory>
#include< string>
#include< curl / curl.h>
#include< json / json.h>
namespace
{
std :: size_t callback（
const char * in，
std :: size_t size，
std :: size_t num，
std :: string * out）
{
const std :: size_t totalBytes（size * num）;
out-> append（in，totalBytes）;
return totalBytes;
}
}
int main（）
{
const std :: string url（http://date.jsontest.com/ ）;
CURL * curl = curl_easy_init（）;
//设置远程URL。
curl_easy_setopt（curl，CURLOPT_URL，url.c_str（））;
//不要打扰尝试IPv6，这将增加DNS解析时间。
curl_easy_setopt（curl，CURLOPT_IPRESOLVE，CURL_IPRESOLVE_V4）;
//不要永远等待，10秒后超时。
curl_easy_setopt（curl，CURLOPT_TIMEOUT，10）;
//如有必要，请遵循HTTP重定向。
curl_easy_setopt（curl，CURLOPT_FOLLOWLOCATION，1L）;
//响应信息。
int httpCode（0）;
std :: unique_ptr< std :: string> httpData（new std :: string（））;
//连接数据处理函数。
curl_easy_setopt（curl，CURLOPT_WRITEFUNCTION，callback）;
//连接数据容器（将作为最后一个参数传递给
//回调处理函数）。可以是任何指针类型，因为它将
//内部作为void指针传递。
curl_easy_setopt（curl，CURLOPT_WRITEDATA，httpData.get（））;
//运行我们的HTTP GET命令，捕获HTTP响应代码，并清理。
curl_easy_perform（curl）;
curl_easy_getinfo（curl，CURLINFO_RESPONSE_CODE，& httpCode）;
curl_easy_cleanup（curl）;
if（httpCode == 200）
{
std :: cout< \\\
Got successful response from<< url<< std :: endl;
//响应看起来不错 - 现在使用Curl完成。尝试解析结果
//并打印出来。
Json :: Value jsonData;
Json :: Reader jsonReader;
if（jsonReader.parse（* httpData，jsonData））
{
std :: cout< 成功解析JSON数据< std :: endl;
std :: cout<< \\\
JSON data received：< std :: endl;
std :: cout<< jsonData.toStyledString（）<< std :: endl;
const std :: string dateString（jsonData [date]。asString（））;
const std :: size_t unixTimeMs（
jsonData [milliseconds_since_epoch]。asUInt64（））;
const std :: string timeString（jsonData [time]。asString（））;
std :: cout<< Natively parsed：< std :: endl;
std :: cout<< \tDate string：<< dateString<< std :: endl;
std :: cout<< \tUnix timeMs：< unixTimeMs<< std :: endl;
std :: cout<< \tTime string：<< timeString<< std :: endl;
std :: cout<< std :: endl;
}
else
{
std :: cout< 无法将HTTP数据解析为JSON<< std :: endl;
std :: cout<< HTTP data was：\\\
<< * httpData.get（）< std :: endl;
return 1;
}
}
else
{
std :: cout< Could not GET from<< url<< - exiting< std :: endl;
return 1;
}
return 0;
}
输出如下：
从http://date.jsontest.com/成功响应
成功解析JSON数据
收到的JSON数据：
{
date：03-09-2015，
milliseconds_since_epoch：1425938476314，
time：10:01:16 PM
}
原生解析：
日期字符串：03-09-2015
Unix timeMs：1425938476314
时间字符串：10:01:16 PM
So I've been looking around the internet for a basic example of parsing JSON using libcurl and jsoncpp but I've not been able to find one.
Could someone please point me in the right direction or specify here, a simple example of using libcurl and jsoncpp, downloading json from a specified webpage (the link itself ending in .json so it will be pulling json directly) parsing it and printing it.
All help is appreciated. Thanks!
Euden
Here's a self-contained example to a) HTTP GET a JSON object via libcurl and then b) parse it with JsonCpp. @WhozCraig is correct to say that these are two totally separate activities, but I happen to have a project that does both so I aggregated this small sample that fetches and parses the JSON from this nifty page.
If you put this code in a file called main.cpp, then you can compile, link, and run (assuming libcurl and libjsoncpp are available on your path) with:
g++ main.cpp -ljsoncpp -lcurl -o example.out && ./example.out
// main.cpp
#include <cstdint>
#include <iostream>
#include <memory>
#include <string>
#include <curl/curl.h>
#include <json/json.h>
namespace
{
std::size_t callback(
const char* in,
std::size_t size,
std::size_t num,
std::string* out)
{
const std::size_t totalBytes(size * num);
out->append(in, totalBytes);
return totalBytes;
}
}
int main()
{
const std::string url("http://date.jsontest.com/");
CURL* curl = curl_easy_init();
// Set remote URL.
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
// Don't bother trying IPv6, which would increase DNS resolution time.
curl_easy_setopt(curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
// Don't wait forever, time out after 10 seconds.
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10);
// Follow HTTP redirects if necessary.
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
// Response information.
int httpCode(0);
std::unique_ptr<std::string> httpData(new std::string());
// Hook up data handling function.
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, callback);
// Hook up data container (will be passed as the last parameter to the
// callback handling function). Can be any pointer type, since it will
// internally be passed as a void pointer.
curl_easy_setopt(curl, CURLOPT_WRITEDATA, httpData.get());
// Run our HTTP GET command, capture the HTTP response code, and clean up.
curl_easy_perform(curl);
curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpCode);
curl_easy_cleanup(curl);
if (httpCode == 200)
{
std::cout << "\nGot successful response from " << url << std::endl;
// Response looks good - done using Curl now. Try to parse the results
// and print them out.
Json::Value jsonData;
Json::Reader jsonReader;
if (jsonReader.parse(*httpData, jsonData))
{
std::cout << "Successfully parsed JSON data" << std::endl;
std::cout << "\nJSON data received:" << std::endl;
std::cout << jsonData.toStyledString() << std::endl;
const std::string dateString(jsonData["date"].asString());
const std::size_t unixTimeMs(
jsonData["milliseconds_since_epoch"].asUInt64());
const std::string timeString(jsonData["time"].asString());
std::cout << "Natively parsed:" << std::endl;
std::cout << "\tDate string: " << dateString << std::endl;
std::cout << "\tUnix timeMs: " << unixTimeMs << std::endl;
std::cout << "\tTime string: " << timeString << std::endl;
std::cout << std::endl;
}
else
{
std::cout << "Could not parse HTTP data as JSON" << std::endl;
std::cout << "HTTP data was:\n" << *httpData.get() << std::endl;
return 1;
}
}
else
{
std::cout << "Couldn't GET from " << url << " - exiting" << std::endl;
return 1;
}
return 0;
}
Output looks like:
Got successful response from http://date.jsontest.com/
Successfully parsed JSON data
JSON data received:
{
"date" : "03-09-2015",
"milliseconds_since_epoch" : 1425938476314,
"time" : "10:01:16 PM"
}
Natively parsed:
Date string: 03-09-2015
Unix timeMs: 1425938476314
Time string: 10:01:16 PM
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