JavaScript Object Notation(JSON)Compiled by

Adnan SohailSoftware Engineer

i2c inc.

JSONJSON (JavaScript Object Notation) is a lightweight data-

interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming

Language, Standard ECMA-262 3rd Edition - December 1999.

JSON is a text format that is completely language independent.

These properties make JSON an ideal data-interchange language.

Why JSON?• Because JSON is lightweight, easy to understand,

manipulate and generate, it has almost replaced XML which was used previously as the only data-interchange format.

• JSON is preferable because of the following reasons:– XML is heavier than JSON – to parse XML, we have to use xPath which is an overhead

removed in JSON because JSON is native to JavaScript – XML uses tags to describe user data and tags increase the

size of data

JSON Structures

• JSON is built on two structures:– A collection of name/value pairs. • In various languages, this is realized as an object,

record, dictionary, hash table, keyed list, or associative array.

– An ordered list of values. • In most languages, this is realized as an array, vector,

list, or sequence.

Syntax of JSON

ObjectAn object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are

separated by , (comma).

Syntax of JSON

• Array– An array is an ordered collection of values. – An array begins with [ (left bracket) and ends with ] (right

bracket). Values are separated by , (comma).

Syntax of JSON

• A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.

• A string is a collection of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A character is represented as a single character string. A string is very much like a C or Java string.

JSON Example

{ “students” : [

{“id":1, "name":"Adnan Sohail"},{“id":2, "name":"Irfan Razzaq"}

]}

XML Example<?xml version="1.0" ?><root>

<student><id>1</id><name>Adnan Sohail</name>

</student><student>

<id>2</id><name>Irfan Razzaq</name>

</student></root>

Validating JSON &JSON Security

• JavaScript’s built-in method eval() is used to validate a JSON string.

• Note:– Use eval() only when the source is authentic and trusted

which means use it only if you are sure that the string passed to it is a valid JSON string

• When you’ve security risks usevar myObject = myJSONtext.parseJSON();

• Which is available in http://www.json.org/json.js

– but eval() is faster than parseJSON()

Using JSON APIs

• JSON strings can be easily generated using JSON APIs available at http://json.org

• There are two main classes available in org.json.* package– org.json.JSONObject– org.json.JSONArray

• Strings can be generating from objects of JSONObject or JSONArray using their toString() methods

Benefits of JSON over XML

• JSON supports data types like string, integer, boolean etc.

• JSON is native data format for JavaScript and therefore it faster for the browser to read and understand.

• As JSON contains no tags but data and therefore less data to be transferred between client and the server. So, it’s lighter than XML.

• Easy for humans to read and write.

JSON References

• http://www.xul.fr/en-xml-ajax.html• http://www.xul.fr/ajax-javascript-json.html• http://json.org/• http://www.json.org/java/