How can I parse json and write that data to a database using Sinatra and DataMapper

I'm doing a proof of concept thing here and having a bit more trouble than I thought I was going to. Here is what I want to do and how I am currently doing it.

I am sending my Sinatra app a json file which contains the simple message below.

[ 
        { 
        title: "A greeting!",
        message: "Hello from the Chairman of the Board" 
         }
]

From there I have a post which I am using to take the params and write them to sqlite database

post '/note' do

    data = JSON.parse(params) #<---EDIT - added, now gives error.

    @note = Note.new    :title => params[:title],
                          :message =>  params[:message],
                          :timestamp => (params[:timestamp] || Time.now) 
    @note.save
end

When I send the message the timestamp and the id are saved to the database however the title and message are nil.

What am I missing?

Thanks

Edit:

Now when I run my app and send it the json file I get this error:

C:/Use开发者_JAVA技巧rs/Norm/ruby/Ruby192/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread' TypeError: can't convert Hash into String

Edit 2: Some success.

I have the above json in a file call test.json which is the way the json will be posted. In order to post the file I used HTTPClient:

require 'httpclient'

HTTPClient.post 'http://localhost:4567/note', [ :file => File.new('.\test.json') ]

After thinking about it some more, I thought posting the file was the problem so I tried sending it a different way. The example below worked once I changed n my post /note handle to this:

data = JSON.parse(request.body.read)

My new send.rb

require 'net/http'

require 'rubygems'
require 'json'

@host = 'localhost'
@port = '4567'

@post_ws = "/note"

@payload ={
    "title" => "A greeting from...",
    "message" => "... Sinatra!"
  }.to_json

def post
     req = Net::HTTP::Post.new(@post_ws, initheader = {'Content-Type' =>'application/json'})
          #req.basic_auth @user, @pass
          req.body = @payload
          response = Net::HTTP.new(@host, @port).start {|http| http.request(req) }
           puts "Response #{response.code} #{response.message}:
          #{response.body}"
        end

thepost = post
puts thepost

So I am getting closer. Thanks for all the help so far.

---

Sinatra won't parse the JSON automatically for you, but luckily parsing JSON is pretty straightforward:

Start with requiring it as usual. require 'rubygems' if you're not on Ruby 1.9+:

>> require 'json' #=> true
>> a_hash = {'a' => 1, 'b' => [0, 1]} #=> {"a"=>1, "b"=>[0, 1]}
>> a_hash.to_json #=> "{"a":1,"b":[0,1]}"
>> JSON.parse(a_hash.to_json) #=> {"a"=>1, "b"=>[0, 1]}

That's a roundtrip use to create, then parse some JSON. The IRB output shows the hash and embedded array were converted to JSON, then parsed back into the hash. You should be able to break that down for your nefarious needs.

To get the fields we'll break down the example above a bit more and pretend that we've received JSON from the remote side of your connection. So, the received_json below is the incoming data stream. Pass it to the JSON parser and you'll get back a Ruby data hash. Access the hash as you would normally and you get the values:

>> received_json = a_hash.to_json #=> "{"a":1,"b":[0,1]}"
>> received_hash = JSON.parse(received_json) #=> {"a"=>1, "b"=>[0, 1]}
>> received_hash['a'] #=> 1
>> received_hash['b'] #=> [0, 1]

The incoming JSON is probably a parameter in your params[] hash but I am not sure what key it would be hiding under, so you'll need to figure that out. It might be called 'json' or 'data' but that's app specific.

Your database code looks ok, and must be working if you're seeing some of the data written to it. It looks like you just need to retrieve the fields from the JSON.