Json Library?

[Avilius]

I'm looking for a good, lightweight library that can parse JSON files for configuration data in my game (along with a tutorial).

I want something simple and lightweight (that doesn't use anything except for the standard libraries).

[TwilightSpectre]

JSON is a very easy format to parse, so you generally don't need a library for it (that is one of its main benefits) - you can just make a quick one yourself.

If you want a library anyway, I don't know of any that fullfil your requirements exactly. If you are using the boost library anyway, the Boost.Property_Tree library provides a JSON parser, as well as a very usable interface to retrieve data from it. Its also a header-only template library - what you don't use doesn't add to your executable.

However, if you don't want a dependency of boost, the official JSON website ( http://www.json.org/ )has about 20 conforming JSON parsers for C++ and another 20 or so for C (see near the bottom of the page). You can probably find one you like from those ones.

[Avilius]

I've decided to use Jansson. Thanks.

[10X9216C]

The problem with boost is that it uses strings for all it's types. So if you use boost to generate a json file that is going to be used in javascript or something similar. You'll need to manually convert the values to their appropriate types.

[Avilius]

spectral wrote:

You'll need to manually convert the values to their appropriate types.

I only really needed it as an intermediate format for my game engine; just something that didn't stop my work flow, easy to add onto, and quick to parse. I had no intent to use javascript (or anything remotely similar), and I plan on compiling it to a different format upon release, so this really didn't effect me much (Jansson handles the conversions anyway).

Jansson works great and I'd recommend it to anyone; it was trivial to set it up with cmake and compile it's library (quick as well), and I got a working solution in a matter of minutes with everything set up.

[10X9216C]

Well it is handy information, I ended up using boost without realizing it and when my plans changed and i ended up using the json files with javascript it was a bit too late to change api. I did look at some other libraries before using boost, some of them didn't allow the user to specify the order or just put them in a random/alphabetical order, which kind of mattered with some of the content.

Jansson works great and I'd recommend it to anyone; it was trivial to set it up with cmake and compile it's library (quick as well), and I got a working solution in a matter of minutes with everything set up.

That is just about almost every library out there that uses cmake. That is what cmake is for after all.

[Avilius]

That is just about almost every library out there that uses cmake. That is what cmake is for after all.

Well, my only experience with cmake was when I previously built SFML 2.1 a while ago (I've been using SDL for years and I wanted to see what SFML was about), and there were tons of non-trivial errors with the generation of the project file. I guess I just wasn't aware that it was reliable (which I don't think anymore).

[modoran]

I use cJSON - very lightweight and no setup required, just add cjson.c and cjson.h to your project and you are done.
http://sourceforge.net/projects/cjson/

[ResidentBiscuit]

https://github.com/udp/json-parser

[LB]

I like json-parser because of the granularity in the type system - it is much more fine-grained than JavaScript's type system. I actually needed to port a project to HTML5 and ran into a snag when I found out that JavaScript did not have disparate floating point and integer types. I think it also allows for duplicate keys in objects, which is useful for parsing user-made JSON.

If you don't care about the types of data (e.g. only care if it is a number or not) then the only real benefit of json-parser is the speed and low memory usage (maybe you're parsing a huge amount of data).

If you don't need the speed and don't care about excess memory usage, then use a high level C++ json-parsing library.

[Lowest0ne]

I use jsoncpp because it is in my package management system.

I tried boost, but it wasn't accepting valid json. I had something like this:

{
  [
    { "name" : "john" }
  ]
}

Boost wanted:

{
  "people":
  [
    "person": { "name": "john" }
  ]
}

[LB]

@LowestOne: Your first example was not valid JSON. Objects cannot contain nameless members. Your second example is also not valid JSON - array elements cannot have names.

http://jsonlint.com/

[Lowest0ne]

Then it was something else, that is why I said "something like"

Edit: going back into the project, I had this:

{
  "people":
  [
    { "name", "john" }
  ]
}

If I recall correctly, Boost didn't like the unnamed object inside the array.

[LB]

That's still not valid JSON, you used a comma instead of a colon inside that object.

[Lowest0ne]

lol