C++ JSON parser

Question

Dear reader,

I'm working on a twitter client which uses the twitter streaming json api. Twitter advices JSON as XML version is deprecated. I'm looking for a good JSON parser which can parse the json data below.

I'm receiving this JSON which I want to be able to read/parse using a JSON parser.

{
"in_reply_to_status_id": null,
"text": "Home-plate umpire Crawford gets stung http://tinyurl.com/27ujc86",
"favorited": false,
"coordinates": null,
"in_reply_to_user_id": null,
"source": "<a href=\"http://apiwiki.twitter.com/\" rel=\"nofollow\">API</a>",
"geo": null,
"created_at": "Fri Jun 18 15:12:06 +0000 2010",
"place": null,
"user": {
    "profile_text_color": "333333",
    "screen_name": "HostingViral",
    "time_zone": "Pacific Time (US & Canada)",
    "url": "http://bit.ly/1Way7P",
    "profile_link_color": "228235",
    "profile_background_image_url": "http://s.twimg.com/a/1276654401/images/themes/theme14/bg.gif",
    "description": "Full time Internet Marketer - Helping other reach their Goals\r\nhttp://wavemarker.com",
    "statuses_count": 1944,
    "profile_sidebar_fill_color": "c7b7c7",
    "profile_background_tile": true,
    "contributors_enabled": false,
    "lang": "en",
    "notifications": null,
    "created_at": "Wed Dec 30 07:50:52 +0000 2009",
    "profile_sidebar_border_color": "120412",
    "following": null,
    "geo_enabled": false,
    "followers_count": 2485,
    "protected": false,
    "friends_count": 2495,
    "location": "Working at Home",
    "name": "Johnathan Thomas",
    "verified": false,
    "profile_background_color": "131516",
    "profile_image_url": "http://a1.twimg.com/profile_images/600114776/nessykalvo421_normal.jpg",
    "id": 100439873,
    "utc_offset": -28800,
    "favourites_count": 0
}, "in_reply_to_screen_name": null,
"id": 16477056501,
"contributors": null,
"truncated": false
}

*This is the raw string (above it beautified) *

{"in_reply_to_status_id":null,"text":"Home-plate umpire Crawford gets stung http://tinyurl.com/27ujc86","favorited":false,"coordinates":null,"in_reply_to_user_id":null,"source":"&lt;a href=\"http://apiwiki.twitter.com/\" rel=\"nofollow\">API</a>","geo":null,"created_at":"Fri Jun 18 15:12:06 +0000 2010","place":null,"user":{"profile_text_color":"333333","screen_name":"HostingViral","time_zone":"Pacific Time (US & Canada)","url":"http://bit.ly/1Way7P","profile_link_color":"228235","profile_background_image_url":"http://s.twimg.com/a/1276654401/images/themes/theme14/bg.gif","description":"Full time Internet Marketer - Helping other reach their Goals\r\nhttp://wavemarker.com","statuses_count":1944,"profile_sidebar_fill_color":"c7b7c7","profile_background_tile":true,"contributors_enabled":false,"lang":"en","notifications":null,"created_at":"Wed Dec 30 07:50:52 +0000 2009","profile_sidebar_border_color":"120412","following":null,"geo_enabled":false,"followers_count":2485,"protected":false,"friends_count":2495,"location":"Working at Home","name":"Johnathan Thomas","verified":false,"profile_background_color":"131516","profile_image_url":"http://a1.twimg.com/profile_images/600114776/nessykalvo421_normal.jpg","id":100439873,"utc_offset":-28800,"favourites_count":0},"in_reply_to_screen_name":null,"id":16477056501,"contributors":null,"truncated":false}

I've tried multiple JSON parsers from json.org though I've tried 4 now and can't find one which can parse above json.

Kind regards, Pollux

Answer 1

I'm a real big fan of jsoncpp.

Answer 2

Python 2.6 seems to parse your example fine. However, I did have problems when I initially tried. Python puked as well if I pasted the string directly without escaping the backslashes. Possibly that is related to your issue. Make sure the backslashes aren't being processed along the way. Or try double escaping them.

---

Update: I tried it with JsonCpp 0.5.0, and it worked perfectly fine. I copied your raw string into a file name example_packed.json. It outputs a sorted and pretty printed version.

#include <fstream>
#include <iostream>

#include "json/json.h"

int main()
{
   Json::Value root;
   std::ifstream file("example_packed.json");
   file >> root;
   std::cout << root;
}

I suspect your issue really is just a copy-paste error. If you copy-paste the raw string directly into a c++ string literal the escapes get processed. You'll need to double escape them when in string form. Otherwise, just read it from a file to avoid the confusion.

Answer 3

JSON Spirit doesn't have any problem with a properly escaped input string. Reduced example:

const std::string test =
"{"
"    \"text\": \"Home-plate umpire Crawford gets stung http://tinyurl.com/27ujc86\","
"    \"favorited\": false,"
"    \"source\": \"<a href=\\\"http://apiwiki.twitter.com/\\\" rel=\\\"nofollow\\\">API</a>\","
"    \"user\": {"
"        \"name\": \"Johnathan Thomas\""
"    }"
"}";

int main() {
    namespace js = json_spirit;
    js::mValue top;
    js::read_string(std::string(test), top);
    json_spirit::mObject obj = top.get_obj();
    std::cout 
      << obj["text"     ].get_str()  << "\n"
      << obj["favorited"].get_bool() << "\n"
      << obj["source"   ].get_str()  << "\n"
      << obj["user"     ].get_obj()["name"].get_str();
}

Answer 4

you could try this http://qjson.sourceforge.net/

Answer 5

Hi, did you get this to work? What parser did you end up using? I tried json_spirit -- it works fine on first few json strings but then goes belly up with following error: "value type is 6 not 2". Don't know what that means?

Answer 6

I ended up using jansson which worked extremelly well!