Json Schema 快速入门

JSON 模式是一种基于 JSON 格式定义 JSON 数据结构的规范。它被写在 IETF 草案下并于 2011 年到期。JSON 模式：

• 描述现有数据格式。
• 干净的人类和机器可读的文档。
• 完整的结构验证，有利于自动化测试。
• 完整的结构验证，可用于验证客户端提交的数据。

Json schema 格式

Json schema 本身遵循Json规范，本身就是一个Json字符串，先来看一个例子

{ "$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"]}

我们来看一下json schema 最外层包含以下几个字段

上面只是一个简单的例子，从上面可以看出Json schema 本身是一个JSON字符串，由通过key-value的形式进行标示。
type 和 properties 用来定义json 属性的类型。required 是对Object字段的必段性进行约束。事实上,json Schema定义了json所支持的类型，每种类型都有0-N种约束方式。下一节我们来，细致介绍一下。

Json schema 类型

Object

{ "$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"]}

object类型有三个关键字:type（限定类型）,properties(定义object的各个字段),required（限定必需字段）,如下：
| 关键字 | 描述 | 示例 |
|:------------- |:---------------| ----- |
| type |类型|. |
| properties |定义属性||
| required|必需属性||
| maxProperties |最大属性个数||
| minProperties |最小属性个数||
| additionalProperties |true or false or object|参考|
properties 定义每个属性的名字和类型，方式如上例。

array

{ "$schema": "http://json-schema.org/draft-04/schema#", "title": "Product", "description": "A product from Acme‘s catalog", "type": "array", "items": { "type": "string" }, "minItems": 1, "uniqueItems": true }

array有三个单独的属性:items,minItems,uniqueItems:

string

{ "$schema": "http://json-schema.org/draft-04/schema#", "title": "Product", "description": "A product from Acme‘s catalog", "type": "object", "properties": { "ip": { "mail": "string", "pattern":"w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*" }, "host": { "type": "phoneNumber", "pattern":"((d{3,4})|d{3,4}-)?d{7,8}(-d{3})*" }, }, "required": ["ip", "host"]}

integer

{ "$schema": "http://json-schema.org/draft-04/schema#", "title": "Product", "description": "A product from Acme‘s catalog", "type": "object", "properties": { "name": { "description": "Name of the product", "type": "string" }, "price": { "type": "integer", "minimum": 0, "exclusiveMinimum": true } }, "required": ["id", "name", "price"]}

number

{ "$schema": "http://json-schema.org/draft-04/schema#", "title": "Product", "description": "A product from Acme‘s catalog", "type": "object", "properties": { "name": { "description": "Name of the product", "type": "string" }, "price": { "type": "number", "minimum": 0, "exclusiveMinimum": true } }, "required": ["id", "name", "price"]}

| 关键字 | 描述 | 示例 ||:------------- |:---------------| ----- || minimum |最小值|. || exclusiveMinimum |如果存在 "exclusiveMinimum" 并且具有布尔值 true，如果它严格意义上大于 "minimum" 的值则实例有效。||| maximum |约束属性，最大值||| exclusiveMaximum |如果存在 "exclusiveMinimum" 并且具有布尔值 true，如果它严格意义上小于 "maximum" 的值则实例有效。||| multipleOf |是某数的倍数，必须大于0的整数||

number 关键字可以描述任意长度，任意小数点的数字。number类型的约束有以下几个：

boolean

{"type": "object","properties": {"number": { "type": "boolean" },"street_name": { "type": "string" },"street_type": { "type": "string","enum": ["Street", "Avenue", "Boulevard"]}}}

true or false

enum

{ "type": "object", "properties": { "number": { "type": "number" }, "street_name": { "type": "string" }, "street_type": { "type": "string", "enum": ["Street", "Avenue", "Boulevard"] } }}

也可以这么做

{ "type": "object", "properties": { "number": { "type": "number" }, "street_name": { "type": "string" }, "street_type": ["Street", "Avenue", "Boulevard"] }}

null

进阶

了解了上面的各个类型的定义及约定条件，就可以满足大部分情况了。但为了写出更好的json schema,我们再学习几个关键字

$ref

$ref 用来引用其它schema,
示例如下：

{ "$schema": "http://json-schema.org/draft-04/schema#", "title": "Product set", "type": "array", "items": { "title": "Product", "type": "object", "properties": { "id": { "description": "The unique identifier for a product", "type": "number" }, "name": { "type": "string" }, "price": { "type": "number", "minimum": 0, "exclusiveMinimum": true }, "tags": { "type": "array", "items": { "type": "string" }, "minItems": 1, "uniqueItems": true }, "dimensions": { "type": "object", "properties": { "length": {"type": "number"}, "width": {"type": "number"}, "height": {"type": "number"} }, "required": ["length", "width", "height"] }, "warehouseLocation": { "description": "Coordinates of the warehouse with the product", "$ref": "http://json-schema.org/geo" } }, "required": ["id", "name", "price"] }}

definitions

当一个schema写的很大的时候，可能需要创建内部结构体，再使用$ref进行引用，示列如下：

{ "type": "array", "items": { "$ref": "#/definitions/positiveInteger" }, "definitions": { "positiveInteger": { "type": "integer", "minimum": 0, "exclusiveMinimum": true } }}

allOf

意思是展示全部属性，建议用requires替代

不建议使用，示例如下

{ "definitions": { "address": { "type": "object", "properties": { "street_address": { "type": "string" }, "city": { "type": "string" }, "state": { "type": "string" } }, "required": ["street_address", "city", "state"] } }, "allOf": [ { "$ref": "#/definitions/address" }, { "properties": { "type": { "enum": [ "residential", "business" ] } } } ]}

anyOf

意思是展示任意属性，建议用requires替代和minProperties替代，示例如下：

{ "anyOf": [ { "type": "string" }, { "type": "number" } ]}

oneOf

其中之一

{ "oneOf": [ { "type": "number", "multipleOf": 5 }, { "type": "number", "multipleOf": 3 } ]}

not

非 * 类型
示例

{ "not": { "type": "string" } }