A basic node express app to simulate schema validation.
It includes a middlware that validates the request body and returns validation error if payload does not conform to the schema. Otherwise it will continue the request to the next route/middleware.
Library being used:
- Express
- ajv
- Read about JSON Schema
- JSON schema builder tool
We are using draft version: Draft 2020-12
You can order a coffee or a tea from the cafe by using following requests
- A perfect coffee order ->
POST /order
{
"item": "coffee",
"category": "latte",
"sugar": 0,
"milk": "yes"
}You will get a response
Barista says, "One latte coming your way!"
- A non ideal coffee order ->
POST /order
{
"item": "coffee",
"category": "latte",
"sugar": 2,
"milk": "yes"
}You will get a response
Barista says, "Normally coffee does not go together but thats okay!!"
- An invalid order with missing fields
POST /order
{
"item": "coffee",
"sugar": 2,
"milk": "yes"
}The schema validator will catch this and responds with
[
{
"instancePath": "",
"schemaPath": "#/then/required",
"keyword": "required",
"params": {
"missingProperty": "category"
},
"message": "must have required property 'category'"
}
]- If you are not sure what type of coffee you feel like drinking but you fancy a tea.
POST /order
{
"item": "tea",
"sugar": 2,
"milk": "yes"
}You will get a response
Tea is brewing!!
The schema can be retrieved throught GET /schema endpoint. It kind of looks like:
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"description": "An order for a cafe",
"type": "object",
"properties": {
"item": {
"type": "string"
},
"milk": {
"type": "string"
},
"sugar": {
"type": "number"
},
"category": {
"type": "string"
}
},
"required": [
"item",
"milk",
"sugar"
],
"if": {
"properties": {
"item": {
"const": "coffee"
}
}
},
"then": {
"required": [
"item",
"milk",
"sugar",
"category"
]
},
"else": {
"required": [
"item",
"milk",
"sugar"
]
}
}