时间：2019-05-16 标签：c++libcurljsonrest

Question

我正在尝试使用 libcurl 从 C++ 中的 REST 网页下载 json 文件。 如果我转到网页，以下代码有效，但如果我尝试访问 json 则不会下载....

我认为这应该是一个简单的解决方法，但我找不到任何对此的参考......

如果我转到网页，它会打开 json，但此代码仅返回 text/html； 字符集=utf-8

？？？？？？？？？

CURL *curl;
CURLcode res;
    struct curl_slist *headers=NULL; // init to NULL is important 
    headers = curl_slist_append(headers, "Accept: application/json");   

curl = curl_easy_init();
if(curl) {

    curl_easy_setopt(curl, CURLOPT_URL, "http://web.com/api/json/123");
            curl_easy_setopt(curl, CURLOPT_HTTPGET,1);
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    //curl_easy_setopt(curl, CURLOPT_URL, "http://web.com/123.html");//this works!!!
    res = curl_easy_perform(curl);

    if(CURLE_OK == res) {
        char *ct;
        /* ask for the content-type */
        res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &ct);
        if((CURLE_OK == res) && ct)
            printf("We received Content-Type: %s\n", ct);
    }
}
/* always cleanup */ 
curl_easy_cleanup(curl);

Answer 1

std::string ServerContent::DownloadJSON(std::string URL)
{   
    CURL *curl;
    CURLcode res;
    struct curl_slist *headers=NULL; // init to NULL is important 
    std::ostringstream oss;
    headers = curl_slist_append(headers, "Accept: application/json");  
    headers = curl_slist_append(headers, "Content-Type: application/json");
    headers = curl_slist_append(headers, "charset: utf-8"); 
    curl = curl_easy_init();

    if (curl) 
    {
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_URL, URL.c_str());
        curl_easy_setopt(curl, CURLOPT_HTTPGET,1); 
        curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,writer);
        res = curl_easy_perform(curl);

        if (CURLE_OK == res) 
        { 
            char *ct;         
            res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &ct);
            if((CURLE_OK == res) && ct)
                return *DownloadedResponse;
        }
    }

    curl_slist_free_all(headers);
}


static std::string *DownloadedResponse;

static int writer(char *data, size_t size, size_t nmemb, std::string *buffer_in)
{

    // Is there anything in the buffer?  
    if (buffer_in != NULL)  
    {
        // Append the data to the buffer    
        buffer_in->append(data, size * nmemb);

        // How much did we write?   
        DownloadedResponse = buffer_in;

        return size * nmemb;  
    }

    return 0;

}   

Answer 2

我认为这与 HTTP 服务器上的配置有关。 首先，您应该发送某种类型的指示，表明您期望的是什么类型，例如，添加一个Accept标头，如下所示：

Accept: application/json

如果您没有指定您期望的内容，服务器可能会在响应头Content-Type返回默认的 HTML，这就是curl 。

Answer 3

您是否从 curl 站点的教程代码中尝试过这种方法？ http://curl.haxx.se/libcurl/c/sepheaders.html