JSON Schema is a specification for JSON
based format for defining the structure of JSON data. It was written under IETF
draft which expired in 2011. JSON Schema −
- Describes your existing data format.
- Clear, human- and machine-readable documentation.
- Complete structural validation, useful for
automated testing.
- Complete structural validation, validating
client-submitted data.
-
JSON Schema Validation
Libraries:
There
are several validators currently available for different programming languages.
Currently the most complete and compliant JSON Schema validator available is
JSV.
|
Languages
|
Libraries
|
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C
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WJElement (LGPLv3)
|
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Java
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json-schema-validator (LGPLv3)
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|
.NET
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Json.NET (MIT)
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ActionScript 3
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Frigga (MIT)
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Haskell
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aeson-schema (MIT)
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Python
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Jsonschema
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Ruby
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autoparse (ASL 2.0); ruby-jsonschema
(MIT)
|
|
PHP
|
php-json-schema (MIT). json-schema
(Berkeley)
|
|
JavaScript
|
Orderly (BSD); JSV; json-schema; Matic
(MIT); Dojo; Persevere (modified BSD or AFL 2.0); schema.js.
|
-
JSON Schema Example:
Given
below is a basic JSON schema, which covers a classical product catalog
description –
{
"$schema":"http://json-schema.org/draft-04/schema#",
"title":"Product",
"description":"A product from Acme's catalog",
"type":"object",
"properties":{
"id":{
"description":"The unique identifier for a product",
"type":"integer"
},
"name":{
"description":"Name of the product",
"type":"string"
},
"price":{
"type":"number",
"minimum":0,
"exclusiveMinimum":true
}
},
"required":["id","name","price"]
}
Let's the check various important keywords that can be used
in this schema –
|
S. No.
|
Keyword &
Description
|
|
1
|
$schema
The $schema keyword states that this
schema is written according to the draft v4 specification.
|
|
2
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title
You will use this to give a title to
your schema.
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3
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description
A little description of the schema.
|
|
4
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type
The type keyword defines the first
constraint on our JSON data: it has to be a JSON Object.
|
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5
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properties
Defines various keys and their value
types, minimum and maximum values to be used in JSON file.
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6
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required
This keeps a list of required
properties.
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|
7
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minimum
This is the constraint to be put on the
value and represents minimum acceptable value.
|
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8
|
exclusiveMinimum
If "exclusiveMinimum" is
present and has boolean value true, the instance is valid if it is strictly
greater than the value of "minimum".
|
|
9
|
maximum
This is the constraint to be put on the
value and represents maximum acceptable value.
|
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10
|
exclusiveMaximum
If "exclusiveMaximum" is
present and has boolean value true, the instance is valid if it is strictly
lower than the value of "maximum".
|
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11
|
multipleOf
A numeric instance is valid against
"multipleOf" if the result of the division of the instance by this
keyword's value is an integer.
|
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12
|
maxLength
The length of a string instance is
defined as the maximum number of its characters.
|
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13
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minLength
The length of a string instance is
defined as the minimum number of its characters.
|
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14
|
pattern
A string instance is considered valid if
the regular expression matches the instance successfully.
|
You can check a http://json-schema.org for the complete list of keywords that can be used in
defining a JSON schema. The above schema can be used to test the validity of
the following JSON code −
[
{
"id":2,
"name":"An ice sculpture",
"price":12.50,
},
{
"id":3,
"name":"A blue mouse",
"price":25.50,
}
]
