Mastering Fastify: Leveraging Decorators and Validation in Backend
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Chapter 1: Introduction to Fastify
Fastify is a lightweight framework for Node.js that is specifically designed for building backend web applications. In this article, we will explore how to effectively develop backend applications using Fastify, focusing on the implementation of decorators, as well as the use of validation schemas.
Section 1.1: Understanding Decorators
In Fastify, you can enhance functionality by adding decorators that include getters and setters. For instance, you can create a simple decorator like this:
const fastify = require('fastify')({});
fastify.decorate('foo', {
getter() {
return 'a getter';}
});
fastify.get('/', async function (request, reply) {
reply.send({ hello: fastify.foo });
});
const start = async () => {
try {
await fastify.listen(3000, '0.0.0.0');} catch (err) {
fastify.log.error(err);
process.exit(1);
}
};
start();
In this example, when you access fastify.foo, it will return 'a getter'. Therefore, the response for the / route will be:
{"hello":"a getter"}
Section 1.2: Implementing Request Validation
Fastify also allows you to enforce validation for incoming requests. Here’s how you can define a schema and apply it:
const fastify = require('fastify')({});
fastify.addSchema({
$id: 'http://example.com/',
type: 'object',
properties: {
hello: { type: 'string' }}
});
fastify.post('/', {
handler(request, reply) {
reply.send('hello');},
schema: {
body: {
type: 'array',
items: { $ref: 'http://example.com#/properties/hello' }
}
}
});
const start = async () => {
try {
await fastify.listen(3000, '0.0.0.0');} catch (err) {
fastify.log.error(err);
process.exit(1);
}
};
start();
In this case, if you send a POST request to the / route with a body like:
["abc"]
You will receive 'hello' in the response. If the data does not comply with the specified schema, a 400 error will be returned.
Chapter 2: Conclusion
In summary, Fastify provides powerful features like decorators with getters and setters, as well as the ability to enforce request validation schemas. These tools simplify the development of robust backend applications.