JSON Schema详解

熟悉XML的开发人员都知道，对XML文档的定义有一个XML Schema。

同样，对于JSON文件的定义，也应该有一个JSON Schema以规范JSON文件内容。

JSON Schema用以标注和验证JSON文档的元数据的文档，可以类比于XML Schema。相对于JSON Schema，一个JSON文档就是JSON Schema的一个instance。

1.JSON Schema规范

IETF负责起草相关规范
最新版本是2017-4-15发布的Draft 6
http://json-schema.org/draft-06/schema
2. JSON Schema规范组成

• JSON Schema Core
• JSON Schema Validation
• JSON Hyper-Schema

3. 规范概览
1)Type-specific keywords

{ "type": "string",   "pattern": "^(\\([0-9]{3}\\))?[0-9]{3}-[0-9]{4}$",   "minLength": 2,   "maxLength": 3,   "format": "date-time|email|hostname|ipv4|ipv6|uri" }

{ "type": "number",  "minimum": 0,  "maximum": 100 }{ "type": "integer" }

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

{ "type": "array",  "minItems": 2,  "maxItems": 3,   "items": {    "type": "number"  } }

{ "type": "boolean" }

{ "type": "null" }

组合

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

2)Generic keywords

{  "title" : "Match anything",  "description" : "This is a schema that matches anything.",  "default" : "Default value"}

3)Combining schemas

• not

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

• allOf

{  "allOf": [    { "type": "string" },    { "maxLength": 5 }  ]}

• anyOf

{  "anyOf": [    { "type": "string", "maxLength": 5 },    { "type": "number", "minimum": 0 }  ]}

• oneOf

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

4)$schema keyword
"$schema": "http://json-schema.org/schema#"
"$schema": "http://json-schema.org/draft-06/schema#"
5)Regular Expressions
6)$ref keyword

• 基本复用

{ "$ref": "#/currentdoc/definitions/address" }

或
{ "$ref": "asidedoc_definitions.json#/address" }

• id设置基本URI

"id": "http://foo.bar/schemas/address.json"
{ "$ref": "person.json" }

• 扩展复用

"shipping_address": {  "allOf": [    // Here, we include our "core" address schema...    { "$ref": "#/definitions/address" },    // ...and then extend it with stuff specific to a shipping    // address    { "properties": {        "type": { "enum": [ "residential", "business" ] }      },      "required": ["type"]    }  ]}

4. 解析软件

• Java

https://github.com/everit-org/json-schema
https://github.com/java-json-tools/json-schema-validator
https://github.com/networknt/json-schema-validator

• Python

https://github.com/Julian/jsonschema
https://github.com/zyga/json-schema-validator

• Online

http://jsonschemalint.com/

参考链接：

http://json-schema.org/