Choose the right JSON schema to apply to your routes based on your constraints.
With this plugin, you will be able to set multiple schemas per route
and, programmatically,
choose which one applies.
Ex: you can choose which JSON schema to apply, based on the req.headers
values.
npm install fastify-schema-constraint
Plugin version | Fastify version |
---|---|
^1.0.0 |
^2.0.0 |
^2.0.0 |
^3.0.0 |
^3.0.0 |
^4.0.0 |
This plugin will act on preHandler
hook and will verify if the payload of the body
, querystring
,
params
or headers
fulfil the constraint condition.
// Define the set of your JSON Schema. They MUST be in an array assigned to `oneOf` property
const routeSchema = {
oneOf: [
{ $id: '#schema1', type: 'object', properties: { mul5: { type: 'number', multipleOf: 5 } } },
{ $id: '#schema2', type: 'object', properties: { mul3: { type: 'number', multipleOf: 3 } } },
{ $id: '#schema3', type: 'object', properties: { mul2: { type: 'number', multipleOf: 2 } } }
]
}
// Define your constraint logic
const constraint = {
body: {
constraint: function (request) {
switch(request.headers.myHeader){
case 1: return '#schema1'
case 2: return '#schema3'
case 3: return '#schema2'
default: return null // it means "don't apply any constraint"
}
},
statusCode: 412, // Optionally define a custom status code in case of errors
errorMessage: 'This constraint return only #schema1' // Optionally define a custom error message
},
querystring: { ... },
params: { ... },
headers: { ... }
}
const fastify = Fastify()
fastify.register(require('fastify-schema-constraint'), constraint)
fastify.route({
url: '/:mul5',
method: 'POST',
handler: (_, reply) => { reply.send('hi') },
schema: {
body: routeSchema,
querystring: routeSchema,
params: routeSchema,
headers: routeSchema
}
})
The options accept a json in this format:
const constraint = {
body: { ... }, // constraint to apply on body
querystring: { ... }, // constraint to apply on query string
params: { ... }, // constraint to apply on path parameters
headers: { ... } // constraint to apply on headers
}
All the fields are optional, but you must provide almost one of these settings.
If you provide a constraint for body
, but the route doesn't have any schema configured
the plugin will skip the constraint.
Each constraint field accepts a json in this format:
{
constraint: function (request) {
// This field is mandatory and must be set with a function.
// The input paramenter is the Fastify request.
// This function must be sync and must return a string with the JSON Schema $id to constraint
return '#idToApply'
},
statusCode: 412, // Optionally: set a custom status code in case of errors, default 400
errorMessage: 'This constraint return only #idToApply' // Optionally: set a custom error message
}
NB:
- if the constraint function returns something different than a string, the validation will be skipped!
- if the constraint function throws an error, an error will be thrown
- if the returned
$id
isn't present in theoneOf
array an error will be thrown - if the payload verified doesn't match with the returned
$id
, an error will be thrown
Copyright Manuel Spigolon, Licensed under MIT.