| 130th | Top computing and IT abbreviations |
| Filename extension | .json |
|---|---|
| Internet media type | application/json |
| Type of format | Data interchange |
| Extended from | JavaScript |
| Standard(s) | RFC 4627 |
| Website | http://json.org |
Wikis
Quiz
Searchapplication/json.^ .json.
Contents |
json.org website provides a comprehensive listing of existing JSON bindings, organized by language.^ true and false)null{ "firstName": "John", "lastName": "Smith", "age": 25, "address": { "streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": "10021" }, "phoneNumber": [ { "type": "home", "number": "212 555-1234" }, { "type": "fax", "number": "646 555-4567" } ], "newSubscription": false, "companyName": null }
<Person> <firstName>John</firstName> <lastName>Smith</lastName> <age>25</age> <address> <streetAddress>21 2nd Street</streetAddress> <city>New York</city> <state>NY</state> <postalCode>10021</postalCode> </address> <phoneNumber type="home">212 555-1234</phoneNumber> <phoneNumber type="fax">646 555-4567</phoneNumber> <newSubscription>false</newSubscription> <companyName /> </Person>
application/json.^ eval() function.^ contact.^ var p = eval("(" + contact + ")");
contact variable must be wrapped in parentheses to avoid an ambiguity in JavaScript's syntax.^ var p = JSON.parse(contact);
p.firstName, p.address.city, p.phoneNumbers[0] etc.^ eval() and use JSON.parse() or another JSON-specific parser instead.^ url with a JSON-formatted string.^ var the_object = {}; var http_request = new XMLHttpRequest(); http_request.^JSONObject; var http_request = new XMLHttpRequest(); http_request.open( "GET", url, true ); http_request.onreadystatechange = function () { if ( http_request.readyState == 4 ) { if ( http_request.status == 200 ) { JSONObject = eval( "(" + http_request.responseText + ")" ); alert( "Hello " + JSONObject.name + "!"
An Introduction to JavaScript Object Notation (JSON) 2 February 2010 8:19 UTC www.webreference.com [Source type: FILTERED WITH BAYES]
open( ."GET", url, true ); http_request.^JSONObject; var http_request = new XMLHttpRequest(); http_request.open( "GET", url, true ); http_request.onreadystatechange = function () { if ( http_request.readyState == 4 ) { if ( http_request.status == 200 ) { JSONObject = eval( "(" + http_request.responseText + ")" ); alert( "Hello " + JSONObject.name + "!"
An Introduction to JavaScript Object Notation (JSON) 2 February 2010 8:19 UTC www.webreference.com [Source type: FILTERED WITH BAYES]
onreadystatechange = function () { if ( http_request.readyState == 4 && http_request.status == 200 ) { the_object = JSON.parse( http_request.responseText ); } }; http_request.send(null);
<iframe> elements to asynchronously request JSON data in a cross-browser fashion, or use simple <form action="url_to_cgi_script" target="name_of_hidden_iframe"> submissions.^ <script> tags can also be used to transport JSON data.^ eval()eval() function, which was designed to evaluate JavaScript expressions.^ eval.^ var my_JSON_object = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \r ]/.test( text.replace(/"(\\.|[^"\\])*"/g, ''))) && eval('(' + text + ')');
parseJSON(), has been proposed as a safer alternative to eval, as it is specifically intended to process JSON data and not JavaScript.^ eval() security problem above.^ <script> tags, which can retrieve data from locations other than domain1.com.^ <script> tags, some pages use them to retrieve JSON from other origins.^ {"Name": "Cheeso", "Rank": 7}
<script type="text/javascript" src="http://domain1.com/getjson?jsonp=parseResponse"></script>
parseResponse({"Name": "Cheeso", "Rank": 7})
<script> tag does not respect the same origin policy in web browser implementations, a malicious page can request and obtain JSON data belonging to another site.^ | Filename extension |
.json |
|---|---|
| Internet media type |
application/json |
| Type of format | Data interchange |
| Extended from | JavaScript |
| Standard(s) | RFC 4627 |
| Website | http://json.org |
JSON (an acronym for JavaScript Object Notation (pronounced /dʒeɪsɔːn/)) 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. Despite its relationship to JavaScript, it is language-independent, with parsers available for virtually every programming language.
The JSON format was originally specified by Douglas Crockford, and is described in RFC 4627. The official Internet media type for JSON is application/json. The JSON filename extension is .json.
The JSON format is often used for serializing and transmitting structured data over a network connection. It is primarily used to transmit data between a server and web application, serving as an alternative to XML.
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Douglas Crockford was the first to specify and popularize the JSON format.[1]
JSON was used at State Software, a company co-founded by Crockford, starting around 2001. The JSON.org website was launched in 2002. In December 2005, Yahoo! began offering some of its web services in JSON.[2] Google started offering JSON feeds for its GData web protocol in December 2006.[3]
Although JSON was based on a subset of the JavaScript programming language (specifically, Standard ECMA-262 3rd Edition—December 1999[4]) and is commonly used with that language, it is considered to be a language-independent data format. Code for parsing and generating JSON data is readily available for a large variety of programming languages. json.org provides a comprehensive listing of existing JSON libraries, organized by language.
JSON's basic types are:
true or false)
null
The following example shows the JSON representation of an object that describes a person. The object has string fields for first name and last name, a number field for age, contains an object representing the person's address, and contains a list (an array) of phone number objects.
"firstName": "John",
"lastName": "Smith",
"age": 25,
"address":
{
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": "10021"
},
"phoneNumber":
[
{
"type": "home",
"number": "212 555-1234"
},
{
"type": "fax",
"number": "646 555-4567"
}
]
}
A strictly bijective equivalent for the above in XML could be:
firstName John lastName Smith age 25 address phoneNumber
Since JSON is a subset of JavaScript it is possible (but not recommended) to parse the JSON text into an object by invoking JavaScript's eval() function. For example,
if the above JSON data is contained within a JavaScript string variable contact, one could use it to create the JavaScript object p like so:
var p = eval("(" + contact + ")");
The contact variable must be wrapped in parentheses to avoid an ambiguity in JavaScript's syntax.[5]
The recommended way, however, is to use a JSON parser. Unless a client absolutely trusts the source of the text, or must parse and accept text which is not strictly JSON-compliant, one should avoid eval(). A correctly implemented JSON parser will accept only valid JSON, preventing potentially malicious code from running.
Modern browsers, such as Firefox 3.5 and Internet Explorer 8, include special features for parsing JSON. As native browser support is more efficient and secure than eval(), it is expected that native JSON support will be included in the next ECMAScript standard.[6]
There are several ways to verify the structure and data types inside a JSON object, much like an XML schema.
JSON Schema[7] is a specification for a JSON-based format for defining the structure of JSON data. JSON Schema provides a contract for what JSON data is required for a given application and how it can be modified, much like what XML Schema provides for XML. JSON Schema is intended to provide validation, documentation, and interaction control of JSON data. JSON Schema is based on the concepts from XML Schema, RelaxNG, and Kwalify, but is intended to be JSON-based, so that JSON data in the form of a schema can be used to validate JSON data, the same serialization/deserialization tools can be used for the schema and data, and it can be self descriptive.
The following JavaScript code shows how the client can use an XMLHttpRequest to request an object in JSON format from the server. (The server-side programming is omitted; it has to be set up to respond to requests at url with a JSON-formatted string.)
if (http_request.readyState == 4 && http_request.status == 200){
my_JSON_object = JSON.parse( http_request.responseText );
}
}; http_request.send(null);
Note that the use of XMLHttpRequest in this example is not cross-browser compatible; syntactic variations are available for Internet Explorer, Opera, Safari, and Mozilla-based browsers. The usefulness of XMLHttpRequest is limited by the same origin policy: the URL replying to the request must reside within the same DNS domain as the server that hosts the page containing the request. Alternatively, the JSONP approach incorporates the use of an encoded callback function passed between the client and server to allow the client to load JSON-encoded data from third-party domains and to notify the caller function upon completion, although this imposes some security risks and additional requirements upon the server.
Browsers can also use <iframe> elements to asynchronously request JSON data in a cross-browser fashion, or use simple submissions. These approaches were prevalent prior to the advent of widespread support for XMLHttpRequest.
Dynamic
The server then wraps its JSON response with this prefix, or "padding", before sending it to the browser. When the browser receives the wrapped response from the server it is now a script, rather than simply a data declaration. In this example, what is received is
...which can cause a change of state within the browser's execution context, because it invokes a method.
While the padding (prefix) is typically the name of a callback function that is defined within the execution context of the browser, it may also be a variable assignment, an if statement, or any other Javascript statement prefix.
But to make a JSONP call, you need a script tag. Therefore, for each new JSONP request, the browser must add a new
parseResponse({"Name": "Cheeso", "Rank": 7})
The Padding
Script Tag Injection
Related links
Up to date as of November 16, 2009
Using JSON with Yahoo! Web services - Using JSON with Yahoo! Web Services - YDN
AJAX without XML - Software Secret Weapons: AJAX Without XML
Speeding Up AJAX with JSON - Speeding Up AJAX with JSON
JSON AJAX Chat Tutorial - JSON AJAX Web Chat Tutorial
Using JSON with Google Data APIs - Using JSON with Google Data APIs - Google Data APIs - Google Code
The Limitations of JSON - The limitations of JSON
JSON Formatter - JSON Formatter (& Validator!)
JSON Discussion Group - json : JSON JavaScript Object Notation
Accelerating AJAX based Web Client Development with JSON and GWT - TechForb: Accelerating AJAX based Web Client Development with JSON and GWT
Yahoo JSON - Using JSON with Yahoo! Web Services - YDN
JSON in JavaScript without eval() - the proper way - Computers & Philosophy: JSON, AJAX, & PHP
Ajax.NET Professional - Ajax.NET Professional Examples
JSON Java Library - Maven - Json-lib::Welcome
Ajax.NET Library - Ajax.NET Professional Examples
Json.NET - Json.NET - James Newton-King
Jayrock - Jayrock: JSON and JSON-RPC for .NET
http://sourceforge.net/projects/lkjson/ - JSON delphi library | Get JSON delphi library at SourceForge.net
BarracudaDrive - BarracudaDrive command line and scripting tutorial
JSONTools - JSON Tools - Home
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