header-constraint-strategy v2.0.0
header-constraint-strategy
A general purpose find-my-way
custom constraint strategy.
Tested for Fastify ✅!
This module let you to drive the incoming HTTP request into a route based on the header's strict content. Doing so, if a request has a specific string header, it can reach a route hide behind a constraint. Go to the Usage section to get a complete overview of this feature!
Install
npm install header-constraint-strategy
Usage with Fastify
Here all the constraint types you can define with this module!
This setup shows you all the settings header-constraint-strategy
provides to you.
const headerConstraintStrategy = require('header-constraint-strategy')
const Fastify = require('fastify')
// STEP 1: setup the constraints into your fastify instance
const app = Fastify({
constraints: {
// basic usage
foo: headerConstraintStrategy('foo'),
// strict usage
mustBeIn: headerConstraintStrategy({ header: 'mustBeIn', mustMatchWhenDerived: true }),
// custom header usage
appOption: headerConstraintStrategy({ name: 'appOption', header: 'x-my-app' })
}
})
// STEP 2: use the constraint where you need them
app.get('/', {
handler: reply('no constraint')
})
app.get('/', {
handler: reply('foo'),
constraints: {
foo: 'bar'
}
})
app.get('/', {
handler: reply('mustBeIn'),
constraints: {
mustBeIn: '123'
}
})
app.get('/', {
handler: reply('appOption'),
constraints: {
appOption: 'ABC'
}
})
app.get('/', {
handler: reply('mustBeIn and appOption'),
constraints: {
mustBeIn: '123',
appOption: 'ABC'
}
})
app.listen(80)
The routes can be reached via an HTTP request with these headers.
# | foo header | mustBeIn header | x-my-app header | response |
---|---|---|---|---|
1 | - | - | - | 200 - no constraint |
2 | bar | - | - | 200 - foo |
3 | hello | - | - | 200 - no constraint |
4 | - | 123 | - | 200 - mustBeIn |
5 | - | 456 | - | 404 |
6 | - | - | ABC | 200 - appOption |
7 | - | 123 | ABC | 200 - mustBeIn and appOption |
8 | - | ops | ABC | 404 |
9 | bar | 123 | ABC | 200 - mustBeIn and appOption |
10 | bar | ops | ABC | 404 |
Cases explanation
1) When the is not headers that meets the constraint, the route without constraint will be used if set. Otherwise 404
2) The foo
constraint is matched
3) The foo
constraint is not matched so the route without constraint is used
4) The mustBeIn
constraint is matched
5) Like the 4), but this time the route without constraint is no used because of the flag mustMatchWhenDerived: true
6) The appOption
constraint is matched
7) Multiple constraint matches
8) Regardless the appOption
constraint is matched, the mustBeIn
constraint with mustMatchWhenDerived=true
forces the handler to be used
9) When there are multiple matches (the route with foo
and route with mustBeIn
and appOption
), the route with more fulfilled constraint wins!
10) As the 8), the mustBeIn
constraint is not fulfilled
Options
You can pass the following options during the registration:
Option | Default | Description |
---|---|---|
name | as the header if not set | The name of the JSON property that you will set in the route's constraints option |
header | as the name if not set | The HTTP header where read the input to match the constraint |
mustMatchWhenDerived | false | Define if the same route without constraint must be evaluated for the routing. You can translate it as: is this constraint mandatory? |
License
Copyright Manuel Spigolon, Licensed under MIT.