If you are an hapi
developer, you may know the joi
library. It is a powerful validation library that allows you to define programmatic schemas for your data and validate them with ease.
One of the hardest things about migrating from hapi
to fastify
is the complexity thats involved for you to be able to keep using joi
for the route's input validation.
But now, thanks to the joi-compiler
library, you can use joi
with fastify
without any problem!
Note If you have been afraid to use it because it has very few downloads, don't worry it is a new library and I'm the author. And, if you don't know me, I'm a Fastify core maintainer and I'm the co-author of the Fastify book too!
The joi-compiler
module replaces the default ajv
schema compiler with a joi
-based one and allows you to use joi
schemas to validate your data. Let's see how to use it!
Integrate joi
with fastify
After you have installed the latest fastify@4
and joi-compiler
module:
mkdir fastify-joi
cd fastify-joi
npm init -y
npm install --save fastify@4 joi-compiler
We can create a simple index.js
file with the following content:
const fastify = require('fastify')
const JoiCompiler = require('joi-compiler')
// Instantiate the compiler
const joiCompilerInstance = JoiCompiler()
// Install it to Fastify
const app = fastify({
schemaController: {
bucket: joiCompilerInstance.bucket,
compilersFactory: {
buildValidator: joiCompilerInstance.buildValidator
}
}
})
// Use it!
const joiSchema = joiCompilerInstance.joi.object({
foo: joiCompilerInstance.joi.string().required()
})
app.get('/', {
handler: () => 'Hello World!',
schema: {
headers: joiSchema
}
})
app.listen({ port: 3000 })
If you run this code, you will be able to test the joi
validation with the following command:
curl -X GET http://localhost:3000/
# {"statusCode":400,"error":"Bad Request","message":"\"foo\" is required"}
curl -X GET http://localhost:3000/ -H "foo: bar"
# Hello World!
As you can see, the joi
schema is working as expected! In a few lines of code, we have integrated joi
with fastify
and we are able to use it to validate the input of your application routes.
How it works
The joi-compiler
module is a Fastify schema compiler, it is used by Fastify to build the components during the startup to guarantee the encapsulated feature.
For this reason, the joi-compiler
can be configured in the schemaController
option during the Fastify application creation.
Note
How the Fastify Schema Controller works is out of the scope of this article. But if you want to know more about it, you can read the Fastify book!
How to configure the joi-compiler
The JoiCompiler
accepts an optional configuration object to customize the joi
instance.
The default configuration is:
const joiCompilerInstance = JoiCompiler({
// optionally: provide all the JOI options you need
// Here is all the possible options: https://joi.dev/api/?v=17.9.1#anyvalidatevalue-options
prefs: {
stripUnknown: true
},
// optionally: an array with custom JOI extensions such as `@joi/date`
extensions: [
],
// optionally: if you want to use the async validation. Default: false
asyncValidation: false
})
When you instantiate the joiCompilerInstance
, the returned object has the following properties:
buildValidator
: The function to pass to theschemaController
option of Fastify.bucket
: Thejoi
bucket that contains the schemas when you call theapp.addSchema(joiSchema)
method. You can omit this option if you don't useapp.addSchema
.joi
: A customizedjoi
instance that contains the installedextensions
, if there are any. It is a good practice to use this instance to build your schemas.
How to use ajv
and joi
together!
The power of Fastify is that you can use different schema compilers at the same time! Here is an example of how you can learn from the Fastify book:
const joiCompilerInstance = JoiCompiler()
const app = fastify()
app.post('/ajv', {
handler: (request) => request.body,
schema: {
body: {
type: 'object',
properties: {
toX: { const: 42 },
toY: { const: 50 }
}
}
}
})
app.register(async function pluginJoi (app, opts) {
// Install the joi compiler into this encapsulated context!
app.setSchemaController({
bucket: joiCompilerInstance.bucket,
compilersFactory: {
buildValidator: joiCompilerInstance.buildValidator
}
})
// Let's try to use the external schemas!
app.addSchema({ $id: 'x', $value: 42 })
app.addSchema({ $id: 'y', $value: 50 })
app.post('/joi', {
handler: (request) => request.body,
schema: {
body: Joi.object({
toX: Joi.ref('$x'),
toY: Joi.ref('$y')
})
}
})
})
app.listen({ port: 3000 })
If you run this code, you will be able to use the ajv
and joi
validation in the same application! The ajv
validation will be used for the /ajv
route and the joi
validation will be used for the /joi
route.
Pretty cool, right?
Summary
The joi-compiler
is a powerful tool that allows you to build and manage joi
instances for Fastify out of the box in a few lines of code. If you're a joi
user, joi-compiler
is definitely worth checking out!
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