Rest endpoint lifecycle

Overview

All the REST endpoints follow the same lifecycle. The @rest decorator provides lifecycle hooks to all steps.

1. preFetch
2. (submodels only) fetchParent
   1. fetch
   2. postFetch
3. fetch
4. postFetch
5. persist
6. preSend

Steps

preFetch

This step is responsible of the alteration or rejection of the request before any query is done.

This is usually where the authentication and validation are done.

fetch

This step is the actual call to the database. It is responsible of the creation of the MongoDB query with mongoose.

It executes the query returned by the fetch hook, or uses the default behaviour (see the reference table below).

postFetch

This step is responsible of any post-treatment that requires the fetched entity/entities.

It is typically used for filtering with some complex logic, to cross-checking with other entities or - in the case of a create/update/remove - to do extra checks before persisting the entity. It can also be used to trigger some events (e.g. sending an email).

persist (write methods only)

This step is the actual call to the database when a persistence call is required (i.e. create(), update(), remove(), removeAll()).

This step does not have a lifecycle hook.

The following table shows the mongoose function that are called for each pre-defined method:

method	function
create()	new Model().save()
update()	Model.save()
remove()	Model.deleteOne()
removeAll()	Model.deleteMany()

preSend

This step is responsible of any post-treatment before sending the output, and after the entity has been persisted (if required).

Also, it is not being called in the fetchParent step, while the postFetch step is. This is useful if you want to alter the returned JSON but don’t want it to happen internally in the backend (e.g. filtering hidden fields).

preSend is not called on remove() and removeAll() methods.

fetchParent (submodels only)

This step only happens on submodels endpoint (e.g. /entities/:id/subentities). It is a minimal version of a normal lifecycle on the parent entity (e.g. /entities/:id).

It is only composed of two steps: fetch and postFetch. They work exactly as described in their respective sections, but on the parent model instead of the submodel that the enpoint points to.

Reference table

The following table shows the mongoose functions that are called at fetch and persist step, and indicates if hooks are called or not.

method	preFetch	fetch	postFetch	persist	preSend
all()	✓	✓ default: Model.find()	✓		✓
one()	✓	✓ default: Model.findById()	✓		✓
create()	✓	✓ default: new Model()	✓	entity.save()	✓
update()	✓	✓ default: Model.findById()	✓	entity.save()	✓
remove()	✓	✓ default: Model.findById()	✓	Model.deleteOne()
removeAll()	✓	✓ default: Model.find()	✓	Model.deleteMany()