Where do I start with JSON?

Question

I am complete blank about JSON but I would like to be able to read some data from the URL http://stokercloud.dk/dev/getdriftjson.php?mac=oz8hp and be able to store them im a DB. But I don't know where to start, so I thought I would ask here for hints and maybe some links to samples that I might learn from I know that the output might look confusing, but I have a list of what each item is.

• the file is runtime data from my pelletburner

Answer 1

The JSON specification is the first page to read. The standard is so simple it is easy to understand it from this page.

I found a wider tutorial, with illustrations and more resources. Nice to see.

Here is the conclusion of this web page:

• JSON is a open,text based, light-weight data interchange format specified as RFC4627, came to the developer world in 2005 and it's popularity is increased rapidly.
• JSON uses Object and Array as data structures and strings, number, true, false and null as values. Objects and arrays can be nested recursively.
• Most (if not all) modern programming languages can be used to work with JSON.
• NoSQL databases, which are evolved to get rid of the bottlenecks of the Relational Databases, are using JSON to store data.
• JSON gives developers a power to choose between XML and JSON leading to more flexibility.
• Besides NoSQL, AJAX, Package Management, and integration of APIs to the web application are the major areas where JSON is being used extensively.

IMHO the main point with JSON is that it contains documents, or arrays of documents. There is less data types than with Delphi (e.g. no official date/time, and just one numeric type). It is an exchange format, which is widely used now, and, from my own experiment, easier to work with than XML, from both human and computer sides.

In Delphi, you have several libraries around, mainly:

• SuperObject
• XSuperObject
• dwsJSON
• lkJSON
• DBXJSON which ships with newer versions of Delphi;
• mORMot for Win32/Win64
• SynCrossPlatformJSON

About performance, you can take a look at our blog article. DBXJSON (and the official JSON unit of Delphi) is by far the slowest, and somewhat difficult to work with. Some methods for easy access to the JSON document content are missing. Other libraries are much easier to work with. Our version shipped with mORMot is very fast, as is dwsJSON. SuperObject is slower than those, especially for huge content, and XSuperObject is slow (but cross-platform). Our SynCrossPlatformJSON unit is also cross-platform, very fast, and has a variant-based document access.

Some code using mORMot library:

uses
  SynCrtSock,
  SynCommons;

procedure test;
var json: RawUTF8;
    jsondata: TDocVariantData;
    i: integer;
begin
  json := TWinHttp.Get('http://stokercloud.dk/dev/getdriftjson.php?mac=oz8hp');
  jsondata := DocVariantData(_json(json).jsondata)^;
  for i := 0 to jsondata.Count-1 do
    writeln(jsondata.Values[i]); // here all items are converted back to JSON and written
end;

Answer 2

1. To learn JSON (JavaScript Object Notation), you'd read JSON on Wikipedia.
2. To download data from url, you can use TIdHttp, which is an Http client of Indy framework.
3. To parse JSON, I'd suggest use superobject. It includes great examples in demos directory.

Answer 3

JSON is an interchange form for sending data between anything that needs to have data sent to it. Its simplicity is its strength.

The text is valid javascript and so can be interpreted by any javascript compiler, but is now so popular that virtually every language now has a json parser built in or as a library ( see http://json.org/ scroll down to the bottom).

Basically JSON is a very simple structured text. If you google JSON Library Delphi you should get some solutions or for any other language you want to use.