Lua read/write data in JSON format

jsonStorage.lua

-- load the JSON library.
local Json = require("json")

local JsonStorage = {}

-- Function to save a table.  Since game settings need to be saved from session to session, we will
-- use the Documents Directory
JsonStorage.saveTable = function(t, filename)
    local path = system.pathForFile( filename, system.DocumentsDirectory)
    local file = io.open(path, "w")

    if file then
        local contents = Json.encode(t)
        file:write( contents )
        io.close( file )
        return true
    else
        return false
    end
end

JsonStorage.loadTable = function(filename)
    local path = system.pathForFile( filename, system.DocumentsDirectory)
    local contents = ""
    local myTable = {}
    local file = io.open( path, "r" )

    if file then
        -- read all contents of file into a string
        local contents = file:read( "*a" )
        myTable = Json.decode(contents);
        io.close( file )
        return myTable
    end
    return nil
end

return JsonStorage

json.decode does not work for me.

local Jsondata = require("jsonstrorage")
local json = require("json")

local unpack = unpack or table.unpack

function LoadData()

	data = Jsondata.loadTable("jsonfile")
	if data ~= nil then
	print("Not nill")
	end

	print(tostring(json.decode('[1,2,3,{"x":10}]')))

end


LoadData()

I am using this

Wrong code for linux. Using system in local function will always reproduce attempt to index global 'system' (a nil value)

Because it works on Sola2D game framework i guess (which provide a system.* library)