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Json

Json-schema

前端与服务器端的交互过程，大部分时候是使用的json格式

对于json还是比较了解，可是json-schema是什么？

json–JavaScript Object Notation JavaScript对象表示法

json-schema是一个用于验证json数据格式的工具，它本身也是使用json语言编写的

Json Schema定义了一套词汇和规则，这套词汇和规则用来定义Json元数据，且元数据也是通过Json数据形式表达的。Json元数据定义了Json数据需要满足的规范，规范包括成员、结构、类型、约束等

Json-schema示例

json-schema举例：

{"$schema": "","$id": "","$vocabulary": {"": true,"": true,"": true,"": true,"": false,"": true},"$recursiveAnchor": true,"title": "Core and Validation specifications meta-schema","allOf": [{"$ref": "meta/core"},{"$ref": "meta/applicator"},{"$ref": "meta/validation"},{"$ref": "meta/meta-data"},{"$ref": "meta/format"},{"$ref": "meta/content"}],"type": ["object", "boolean"],"properties": {"definitions": {"$comment": "While no longer an official keyword as it is replaced by $defs, this keyword is retained in the meta-schema to prevent incompatible extensions as it remains in common use.","type": "object","additionalProperties": { "$recursiveRef": "#" },"default": {}},"dependencies": {"$comment": "\"dependencies\" is no longer a keyword, but schema authors should avoid redefining it to facilitate a smooth transition to \"dependentSchemas\" and \"dependentRequired\"","type": "object","additionalProperties": {"anyOf": [{ "$recursiveRef": "#" },{ "$ref": "meta/validation#/$defs/stringArray" }]}}}
}

在上述文件中，有些是json-schema规定的特殊字符，也即具有特殊涵义的字符，我们称之为关键字或保留字，有些是根据我们的需要随便编写的相关内容，

关键字说明

title，description，default，example只作为描述作用，不影响对数据的校验。

对复杂结构的支持包括定义和引用。当多个元素使用相同的校验模式时，可以将相同的结构校验定义成一个“类型”，需要使用该“类型”时，可以通过其路径或id来引用

definations-用于定义通用类型模式

定义一个类型，并不需要特殊的关键字。通常的习惯是在root节点的 definations 下面，定义需要多次引用的schema。definations是一个json对象，key是想要定义的“类型”的名称，value是一个json schema

{"definitions": {"address": {//定义的一个通用的模式"type": "object","properties": {"street_address": { "type": "string" },"city":           { "type": "string" },"state":          { "type": "string" }},"required": ["street_address", "city", "state"]}}，"type": "object","properties": {"billing_address": { "$ref": "#/definitions/address" },"shipping_address": { "$ref": "#/definitions/address" }}
}

$ref

上例中定义了一个address的schema，并且在两个地方通过路径的方式引用了它，#/definitions/address表示从根节点开始的路径

$id

{"definitions": {"address": {//定义的一个通用的模式"type": "object","$id" : "address","properties": {"street_address": { "type": "string" },"city":           { "type": "string" },"state":          { "type": "string" }},"required": ["street_address", "city", "state"]}}，"type": "object","properties": {"billing_address": { "$ref": "#address"},"shipping_address": { "$ref":"#address"}}
}

可以在上面的定义中加入id属性，这样可以通过id属性的值对该schema进行引用，而不需要完整的路径。

type

定义模式属性的类型，可以是单选也可以提供多个类型:

type的可选值包括：string\number\boolean\array\object\null

仅有一个类型可选：{ "type": "string" }

可以有多个类型可选：{ "type": ["number", "string"] }

当type与enum发生冲突的时候，以type约束为先:

{"type": "string","enum": ["red", "amber", "green", null]
}

null值与"type": "string"冲突，此时若选值null则检测不通过

约束条件

string 类型的约束条件

format包括"date", “time”, “date-time”, “email”, “hostname”,“ipv4”,"uri"等
“json-pointer”,“regex”

number类型的约束条件

number:数字类型
integer:必须是整数

array类型的约束条件

示例：

  "type": "array","items": [{//0"type": "number"},{//1"type": "string"},{//2"type": "string","enum": ["Street", "Avenue", "Boulevard"]},{//4"type": "string","enum": ["NW", "NE", "SW", "SE"]}],"minItems": 1,"maxItems": 5,"additionalItems": {"type": "string","minLength": 2},"uniqueItems": true
}

items & additionalItems

items列出了多个约束条件时，对应索引的项如果存在必须符合约束条件

• additionalItems属性不存在

  • 数组长度小于items，只要存在的项符合约束条件即可，也即数组长度可以小于items
  • 数组长度大于items且额外元素没有约束条件

• 存在additionalItems属性，数组的长度受限于 additionalItems：

  • 数组长度若小于items，只要存在的项符合约束条件即可，不受 additionalItems影响
  • 如果additionalItems为true，没有额外约束,数组长度可以大于items,因为后面的元素没有对应索引的items约束条件因此无约束

示例：

{"type": "array","items": [{"type": "number"},{"type": "string"},{"type": "string","enum": ["Street", "Avenue", "Boulevard"]},{"type": "string","enum": ["NW", "NE", "SW", "SE"]}],"additionalItems": true
}

• 如果additionalItems 有额外的约束，额外的元素必须符合additionalItems 的约束条件

  "type": "array","items": [{//0"type": "number"},{//1"type": "string"}],"minItems": 1,"maxItems": 5,"additionalItems": {"type": "string","minLength": 2},"uniqueItems": true
}

• 如果additionalItems为 false，数组长度只能<=items的长度

{"type": "array","items": [{"type": "number"},{"type": "string"},{"type": "string","enum": ["Street", "Avenue", "Boulevard"]},{"type": "string","enum": ["NW", "NE", "SW", "SE"]}],"additionalItems": false
}

contains(New in draft 6)

示例：

{"type": "array","contains": {"type": "number"}
}
e.g :["life", "universe", "everything", 42]//最少有一个符合条件

object类型的约束条件

propertyNames(New in draft 6)

示例：

{"type": "object","propertyNames": {"pattern": "^[A-Za-z_][A-Za-z0-9_]*$"}
}

const(New in draft 6)

设定值后不允许属性设置为其他值

{ “const”: “United States of America” }
等价于
{ “enum”: [ “United States of America” ] }

dependencies

属性间的依赖

{"type": "object","properties": {"name": { "type": "string" },"credit_card": { "type": "number" },"billing_address": { "type": "string" }},"required": ["name"],"dependencies": {"credit_card": ["billing_address"],"billing_address": ["credit_card"]}
}

单独定义依赖的属性模式

{"type": "object","properties": {"name": { "type": "string" },"credit_card": { "type": "number" }},"required": ["name"],"dependencies": {//credit_card依赖的属性"credit_card": {"properties": {"billing_address": { "type": "string" }},"required": ["billing_address"]}}
}

只要credit_card属性存在，billing_address必须存在

additionalProperties

用法类似于additionalItems

additionalProperties不受properties与patternProperties的约束条件限制

{"type": "object","properties": {"builtin": { "type": "number" }},"patternProperties": {"^S_": { "type": "string" },"^I_": { "type": "integer" }},"additionalProperties": { "type": "string" }
}

逻辑组合的约束条件

需要注意，使用allOf时，Schema不论在内嵌的Schema里还是外部的Schema里，都不应该使"additionalProperties"为false。否则可能会生成任何数据都无法满足的矛盾Schema。

非json格式数据转化（New in draft 7）

{"type": "string","contentEncoding": "base64","contentMediaType": "image/png"
}

if then else

{"type": "object","properties": {"street_address": {"type": "string"},"country": {"enum": ["United States of America", "Canada"]}},"if": {"properties": { "country": { "const": "United States of America" } }},"then": {"properties": { "postal_code": { "pattern": "[0-9]{5}(-[0-9]{4})?" } }},"else": {"properties": { "postal_code": { "pattern": "[A-Z][0-9][A-Z] [0-9][A-Z][0-9]" } }}
}

以下示例通过 if then实现了 allOf 等同于 oneOf

{"type": "object","properties": {"street_address": {"type": "string"},"country": {"enum": ["United States of America", "Canada", "Netherlands"]}},"allOf": [{"if": {"properties": { "country": { "const": "United States of America" } }},"then": {"properties": { "postal_code": { "pattern": "[0-9]{5}(-[0-9]{4})?" } }}},{"if": {"properties": { "country": { "const": "Canada" } }},"then": {"properties": { "postal_code": { "pattern": "[A-Z][0-9][A-Z] [0-9][A-Z][0-9]" } }}},{"if": {"properties": { "country": { "const": "Netherlands" } }},"then": {"properties": { "postal_code": { "pattern": "[0-9]{4} [A-Z]{2}" } }}}]
}

本文标签： Json