基于libcurl的与es进行通信（C++代码）

Elasticsearch可以通过http报文和json语句来进行增删查改，可以通过libcurl构造语句，去发送到es集群进行操作。参考

https://blog.csdn.net/xsdxs/article/details/72849796

https://stackoverflow.com/questions/25887453/how-to-use-libcurl-in-c-to-send-post-to-elasticsearch

实现一个简便的esclient（）函数，方便读写

运行结果：

图1是查询单条语句的结果

图2是批量查询的结果

图3是以上程序运行前的图

图4是以上程序运行后的图

附录：以上源码

```

    #include

    #include

    #include

    #include

    #include

    using namespace std;

    size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream)

    {

        strncat((char *)stream, (char *)ptr, size*nmemb);

        return size * nmemb;

    }

    int esclient(const string &_http, const string &_json, const string &_command)

    {

            CURL *curl;

            CURLcode res;

            struct curl_slist* headers = NULL;        

            curl = curl_easy_init();

            curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);

            curl_easy_setopt(curl, CURLOPT_URL, _http.c_str());

            headers=curl_slist_append(headers, "Content-Type:application/json");

            curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

            char out[40960]={0};        

            curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);

            curl_easy_setopt(curl, CURLOPT_WRITEDATA, &out);

            if(_command=="delete")

            {

                    curl_easy_setopt(curl,  CURLOPT_CUSTOMREQUEST, "DELETE");

            }

            else if(_command=="get")

            {                

                    curl_easy_setopt(curl,  CURLOPT_CUSTOMREQUEST, "GET");                

            }

            else

            {

                    curl_easy_setopt(curl,  CURLOPT_CUSTOMREQUEST, "POST");

            }

            if(!_json.empty())

            {

                    curl_easy_setopt(curl,CURLOPT_POSTFIELDS,_json.c_str());

                    curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,_json.length());

            }

            res = curl_easy_perform(curl);

           printf("%s\n",out);

            curl_easy_cleanup(curl);

            return res;

    }

    int main(void)

    {

            esclient("http://172.31.100.114:9200/customer/external/1","","get");        //查询单条数据

            esclient("http://172.31.100.114:9200/bank/_search","","search");        //批量查询数据，但是只返回10条，如需其他要求，加json语句

            esclient("http://172.31.100.114:9200/customer/external/3/"," { \"name\": \"hhh\" }","add");                //增加一条数据

            esclient("http://172.31.100.114:9200/customer/external/2/_updata/"," {\"doc\": { \"name\": \"eee\" }}","updata");        //更新某条数据

            esclient("http://172.31.100.114:9200/ccc","","delete");                //删除索引

            esclient("http://172.31.100.114:9200/customer/external/_delete_by_query"," {\"query\":{ \"match\":{\"name\": \"hhh\" }}}","");        //匹配删除数据

    }

```