Enterprise Interface Architecture:
JSON Schema

Tomasz Ducin

17th June 2015, Warsaw

#10

Tomek Ducin

JavaScript, Java, Python

senior software consultant @ Cybercom Poland

blah, blah, blah...

@tomasz_ducin

ducin

ducin.it

Enterprise Interface Architecture

?

Agenda

JSON
schemas
JSON Schema
JSON Schema - Tool Stack

Douglas Crockford

creator of JSON

JSON:

brought to you by

Java Script Object Notation

defining object literals: {} and []
their values might be:
- string (enclosed with ")
- number (double type)
- constant: false, true, null
allows unlimited nesting
flexible: will accept everything

Data Serialization Format

JS

N

YAML

used by

Objective CAML
Perl
PHP
Python
R
REBOL
Ruby
and more...

RFC 7159 vs ECMA-404

QUIZ - is this a valid JSON?

{}
[]
[1,2,3]
{a:1, b:2}
{"a":1, "b":2}
{"a":1, 'b':2}

[{1:2}, []]
[true, false, undefined]
["warsawJS hell yeah!"]
"warsawJS hallelujah!"
true
Number(true)

$

<?xml version="1.0" encoding="UTF-8"?>

<shiporder orderid="889923"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="shiporder.xsd">
  <orderperson>John Smith</orderperson>
  <shipto>
    <name>Ola Nordmann</name>
    <address>Langgt 23</address>
    <city>4000 Stavanger</city>
    <country>Norway</country>
  </shipto>
  <item>
    <title>Empire Burlesque</title>
    <note>Special Edition</note>
    <quantity>1</quantity>
    <price>10.90</price>
  </item>
  <item>
    <title>Hide your heart</title>
    <quantity>1</quantity>
    <price>9.90</price>
  </item>
</shiporder>

<xs:element name="shipto">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="name" type="xs:string"/>
      <xs:element name="address" type="xs:string"/>
      <xs:element name="city" type="xs:string"/>
      <xs:element name="country" type="xs:string"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>

<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name="shiporder">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="orderperson" type="xs:string"/>
      <xs:element name="shipto">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="name" type="xs:string"/>
            <xs:element name="address" type="xs:string"/>
            <xs:element name="city" type="xs:string"/>
            <xs:element name="country" type="xs:string"/>
          </xs:sequence>
        </xs:complexType>
      </xs:element>
      <xs:element name="item" maxOccurs="unbounded">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="title" type="xs:string"/>
            <xs:element name="note" type="xs:string" minOccurs="0"/>
            <xs:element name="quantity" type="xs:positiveInteger"/>
            <xs:element name="price" type="xs:decimal"/>
          </xs:sequence>
        </xs:complexType>
      </xs:element>
    </xs:sequence>
    <xs:attribute name="orderid" type="xs:string" use="required"/>
  </xs:complexType>
</xs:element>

</xs:schema>

JavaScript is dynamically-typed

so is JSON

no compile-time check

communication between components relies on rigid structures

what if the structure changes from one side?

that's where schema comes in

I made 1500 100 900 apps and had no problems with JSON

what to validate?

api communication
configuration
internal app definitions

JSON Schema

XSD for XML
JSON Schema for JSON

JSON Schema

http://json-schema.org/

a specification
JSON used to define JSON
a meta-definition

{
  "type": "boolean"
}

{
  "type": "integer",
  "minimum": 600,
  "maximum": 700,
  "multipleOf": 5,
  "exclusiveMinimum": true
}

{
  "type": "string"
}

true

"WarsawJS"

{
  "type": "array",
  "minItems": 5,
  "items": {
    "enum": [
      "green",
      "blue",
      "yellow"
    ]
  }
}

[
  "green",
  "blue",
  "green",
  "green",
  "yellow",
  "green"
]

{
  "title": "Example Schema",
  "type": "object",
  "properties": {
    "firstName": {
      "type": "string"
    },
    "lastName": {
      "type": "string"
    },
    "age": {
      "description": "Age in years",
      "type": "integer",
      "minimum": 0
    }
  },
  "additionalProperties": false,
  "required": ["firstName", "lastName"]
}

{
  "firstName": "John",
  "lastName": "Lennon",
  "age": 40
}

{
  "firstName": "Paul",
  "lastName": "McCartney"
}

{
  ...
  "properties": {
    "storage": {
      "type": "object",
      "oneOf": [
        { "$ref": "#/definitions/diskDevice" },
        { "$ref": "#/definitions/diskUUID" },
        { "$ref": "#/definitions/nfs" },
        { "$ref": "#/definitions/tmpfs" }
      ]
    }
  }
  ...
}