一、简介

我们先看下面的json数据

{ 
  "id": 1, 
  "name": "g2",　 
  "desc":"b2"
 }

假设, 我们要求id为long型, id、name非空。desc可空。如何衡量json数据是有效的呢？现在流行的json schema 是用来校验json数据是否合法。

详情请移至 https://spacetelescope.github.io/understanding-json-schema/

二、keyWords介绍

1、keyWords速记表

2、具体使用如下

type关键字
①、type = object, properties关键字是必需的。
②、type = array, items关键字是必需的。

porperties关键字

{
      type: "object";
      properties: {
        number: { type: "number" };
        name: { type: "string" };
      };
    }

additionalProperties关键字

"additionalProperties": false ：json串只能出现schema定义的属性。
"additionalProperties": { "type": "string" } ：json串能出现不在schema定义范围内的属性, 但属性的类型必须为string

{
      type: "object";
      properties: { number: { type: "number" }; name: { type: "string" } };
      additionalProperties: false;
}

required关键字
"required": ["name"] ： json串必须出现name属性

{
      type: "object";
      properties: { number: { type: "number" }; name: { type: "string" } };
      additionalProperties: false;
      required: ["name"];
}

dependencies关键字

dependencies": {
    "number": ["name"]
} 

number的出现必须依赖在name的基础上, 换而言之 , number出现,则name必须出现;name的出现与number并没有毛关系

{
      type: "object";
      properties: { number: { type: "number" }; name: { type: "string" } };
      additionalProperties: false;
      required: ["name"];
      dependencies: { number: ["name"] };
}

patternProperties关键字

"patternProperties": {
   "^S_": { "type": "string" },
   "^I_": { "type": "integer" }
}

以s、I开头的属性必须是String类型

{
      type: "object";
      properties: { number: { type: "number" }; name: { type: "string" } };
      additionalProperties: false;
      required: ["name"];
      dependencies: { number: ["name"] };
      patternProperties: {
        "^S_": { type: "string" };
        "^I_": { type: "integer" };
      };
}

enum关键字

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

anyOf关键字
anyOf: 对所有属性范畴生效。所有属性字符串长度最大不能》5

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

allOf关键字
allOf ： type必须相同。不能即String、又number

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

oneOf关键字

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

**not关键字****

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

$schema关键字

schema ： 声明json片段是json schema模式, 并不是 普通json串, 同时也声明了json schema版本

三、拓展

1、复用

{
  "type": "object",
  "properties": {
    "street_address": { "type": "string" },
    "city":           { "type": "string" },
    "state":          { "type": "string" }
  },
  "required": ["street_address", "city", "state"]
}

如果我们想复用上述的json串, 可以使用definitions关键字。json结构定义如下 ：

{
  "definitions": {
    "address": {
      "type": "object",
      "properties": {
        "street_address": { "type": "string" },
        "city":           { "type": "string" },
        "state":          { "type": "string" }
      },
      "required": ["street_address", "city", "state"]
    }
  }
}

如何引用 ？ 可以使用$ref关键字

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

或者
{ "$ref": "definitions.json#/address" }

例子如下 ：
schema定义

{
  "$schema": "http://json-schema.org/draft-04/schema#",
 
  "definitions": {
    "address": {
      "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" }
  }
}

目标匹配json数据

{
  "shipping_address": {
    "street_address": "1600 Pennsylvania Avenue NW",
    "city": "Washington",
    "state": "DC"
  },
  "billing_address": {
    "street_address": "1st Street SE",
    "city": "Washington",
    "state": "DC"
  }
}

2、延伸属性

json schema

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "definitions": {
    "address": {
      "type": "object",
      "properties": {
        "street_address": { "type": "string" },
        "city":           { "type": "string" },
        "state":          { "type": "string" }
      },
      "required": ["street_address", "city", "state"]
    }
  },
  "type": "object",
  "properties": {
    "billing_address": { "$ref": "#/definitions/address" },
    "shipping_address": {
      "allOf": [
        { "$ref": "#/definitions/address" },
        { "properties":
          { "type": { "enum": [ "residential", "business" ] } },
          "required": ["type"]
        }
      ]
    }
  }
}

可匹配json

{
  "shipping_address": {
    "street_address": "1600 Pennsylvania Avenue NW",
    "city": "Washington",
    "state": "DC",
    "type": "business"
  }
}