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JSON interview questions Options
mohansalini
Posted: Monday, May 23, 2011 11:19:55 PM
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Joined: 3/21/2008
Posts: 1
What is The JSON(JavaScript Object Notation) ?

JavaScript Object Notation(JSON) is a lightweight text-based open standard designed for human-readable data interchange. It is derived from the JavaScript programming language for representing simple data structures and associative arrays, called objects. And JSON is language-independent, with parsers available for virtually every programming language. Uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python,php

The JSON format is often used for serializing and transmitting structured data over a network connection. When third party data interchane(REST Services) then JSON may used there LIKE SHOP .It is primarily used to transmit data between a server and web application, serving as an alternative to XML.


Who is the Father or creater of JSON ?
Douglas Crockford called as the Father of JSON

What the file extension of JSON
The JSON filename extension is .json.

Why Use JSON over XML

Lighter and faster than XML as on-the-wire data format
• JSON objects are typed while XML data is typeless
JSON types: string, number, array, boolean,
XML data are all string
• Native data form for JavaScript code
Data is readily accessible as JSON objects in your JavaScript
code vs. XML data needed to be parsed and assigned to variables through tedious DOM APIs
Retrieving values is as easy as reading from an object property in your JavaScript code

Explain JSON Structures
A collection of name/value pairs
In various languages, this is realized as an object, record, struct, 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
• These are universal data structures supported
• A JSON object is an unordered set of name/value pairs
• A JSON 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)

Compare JSON with JavaScript
JSON is a subset of the object literal notation of JavaScript
> JSON can be used in the JavaScript language with no muss or fuss
Example: JSON Object
var myJSONObject = {"bindings": [ {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"},
{"ircEvent": "PRIVMSG", "method": "deleteURI", "regex": "^delete.*"},
{"ircEvent": "PRIVMSG", "method": "randomURI", "regex": "^random.*"}
]
};
• In this example, a JSON JavaScript object is created
containing a single member "bindings", which contains
an array containing three objects, each containing
"ircEvent", "method", and "regex" members
• Members can be retrieved using dot or subscript
operators myJSONObject.bindings[0].method // "newURI"
Text to Object Conversion in
JavaScript code
var myObject = eval('(' + myJSONtext + ')');
• To convert a JSON text into an JSON object, use
the eval() function > eval() invokes the JavaScript compiler
> Since JSON is a proper subset of JavaScript, the compiler will
correctly parse the text and produce an object structure

what the Security and JSON Parser

Security and JSON Parser to understand by below examples
// Include http://www.json.org/json.js
var myObject = myJSONtext.parseJSON();
• eval() can compile and execute any JavaScript program, so there can be security issues (cross-site scripting)
Use eval() when the source can be trusted
• When security is a concern - the source cannot be trusted -, it is better to use a JSON parser
A JSON parser will only recognize JSON text and so is much safer
Object to Text Conversion
var myJSONText = myObject.toJSONString();
• You can convert JSON object into JSON text
• JSON does not support cyclic data structure
Do not give cyclical structures to the JSON stringifier

Do you know JSON Tools for Java Developer

Ya some of JSON tool for java developer is
• Parser
Parse JSON text files and convert these to a Java model
• Renderer
Render a Java representation into text
• Serializer
Serialize plain POJO clusters to a JSON representation
• Validator
Validate the contents of a JSON file using a JSON schema
JSONObject Java Class
• A JSONObject is an unordered collection of name/value pairs
• The put methods adds a name/value pair to an object
• The texts produced by the toString methods strictly conform to the JSON syntax rules
myString = new JSONObject().put("JSON", "Hello, World!").toString();
// myString is {"JSON": "Hello, World"}


How to Generate or Send JSON Data at the Server Side

Create JSONObject Java object
• Add name and value pairs using put method
• Convert it to String type using toString method and send it to the client with content-type as "text/xml" or "text/plain"
myString = new JSONObject().put("JSON", "Hello, World!").toString();
// myString is {"JSON": "Hello, World"}

How to Receive JSON Data at the Client Side

JSON data is received as a string
• Calling eval() will generate JSON object in JavaScript code
> var JSONdata = eval(req.responseText);
• Once you have JSON object, you can use . notation to access its properties
> var name = JSONdata.name;
> var address = JSONdata.addresses[3];
> var streetname = JSONdata.addresses[3].street;


How to Generate/Send JSON Data at the Client Side

Create JSON JavaScript object
• Use "POST" HTTP method in the open method of the XMLHttpRequest object
• Pass JSON JavaScript object in the send method of XMLHttpRequest object
var carAsJSON = JSON.stringify(car);
var url = "JSONExample?timeStamp=" + new Date().getTime(); createXMLHttpRequest();
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlHttp.send(carAsJSON);

How to Receive JSON Data at the Server Side

Read the JSON data as a String type
• Create JSONObject Java object from the string String json = readJSONStringFromRequestBody(request);
//Use the JSON-Java binding library to create a JSON object in Java JSONObject jsonObject = null;
try {
jsonObject = new JSONObject(json);
}
catch(ParseException pe) {
}

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