README
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 |
200 - appOption |
9 | bar |
123 |
ABC |
200 - mustBeIn and appOption |
10 | bar |
ops |
ABC |
200 - appOption |
Cases explanation
- When the is not headers that meets the constraint, the route without constraint will be used if set. Otherwise 404
- The
foo
constraint is matched - The
foo
constraint is not matched so the route without constraint is used - The
mustBeIn
constraint is matched - Like the 4), but this time the route without constraint is no used because of the flag
mustMatchWhenDerived: true
- The
appOption
constraint is matched - Multiple constraint matches
- Only the
appOption
constraint is matched - When there are multiple matches (the route with
foo
and route withmustBeIn
andappOption
), the route with more fulfilled constraint wins! - In case of draws (the route with
foo
and the route withappOption
are metching) wins the last route configured! So in this example, if you move thefoo
route ad the end of the file, the output will change!
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 |
License
Copyright Manuel Spigolon, Licensed under MIT.