npm package: @loopback/boot
Description: A collection of Booters for LoopBack 4 Applications
Author: IBM Corp. and LoopBack contributors
Latest version: 8.0.11

# @loopback/boot

A convention based project Bootstrapper and Booters for LoopBack Applications

## Overview

A Booter is a Class that can be bound to an Application and is called to perform
a task before the Application is started. A Booter may have multiple phases to
complete its task. The task for a convention based Booter is to discover and
bind Artifacts (Controllers, Repositories, Models, etc.).

An example task of a Booter may be to discover and bind all artifacts of a given
type.

A Bootstrapper is needed to manage the Booters and execute them. This is
provided in this package. For ease of use, everything needed is packages using a
BootMixin. This Mixin will add convenience methods such as `boot` and `booter`,
as well as properties needed for Bootstrapper such as `projectRoot`. The Mixin
also adds the `BootComponent` to your `Application` which binds the
`Bootstrapper` and default `Booters` made available by this package.

## Installation

```shell
$ npm i @loopback/boot
```

## Basic Use

```ts
import {Application} from '@loopback/core';
import {BootMixin, Booter, Binding} from '@loopback/boot';
class BootApp extends BootMixin(Application) {}

const app = new BootApp();
app.projectRoot = __dirname;

await app.boot();
await app.start();
```

### BootOptions

List of Options available on BootOptions Object.

| Option         | Type              | Description                         |
| -------------- | ----------------- | ----------------------------------- |
| `controllers`  | `ArtifactOptions` | ControllerBooter convention options |
| `repositories` | `ArtifactOptions` | RepositoryBooter convention options |
| `datasources`  | `ArtifactOptions` | DataSourceBooter convention options |
| `services`     | `ArtifactOptions` | ServiceBooter convention options    |

### ArtifactOptions

| Options      | Type                 | Description                                                                                                  |
| ------------ | -------------------- | ------------------------------------------------------------------------------------------------------------ |
| `dirs`       | `string \| string[]` | Paths relative to projectRoot to look in for Artifact                                                        |
| `extensions` | `string \| string[]` | File extensions to match for Artifact                                                                        |
| `nested`     | `boolean`            | Look in nested directories in `dirs` for Artifact                                                            |
| `glob`       | `string`             | A `glob` pattern string. This takes precedence over above 3 options (which are used to make a glob pattern). |

### BootExecOptions

**Experimental support. May be removed or changed in a non-compatible way in
future without warning**

To use `BootExecOptions` you must directly call `bootstrapper.boot()` and pass
in `BootExecOptions`. `app.boot()` provided by `BootMixin` does not take any
parameters.

```ts
const bootstrapper: Bootstrapper = await this.get(
  BootBindings.BOOTSTRAPPER_KEY,
);
const execOptions: BootExecOptions = {
  booters: [MyBooter1, MyBooter2],
  filter: {
    phases: ['configure', 'discover'],
  },
};

const ctx = bootstrapper.boot(execOptions);
```

You can pass in the `BootExecOptions` object with the following properties:

| Property         | Type                    | Description                                      |
| ---------------- | ----------------------- | ------------------------------------------------ |
| `booters`        | `Constructor<Booter>[]` | Array of Booters to bind before running `boot()` |
| `filter.booters` | `string[]`              | Names of Booter classes that should be run       |
| `filter.phases`  | `string[]`              | Names of Booter phases to run                    |

## Available Booters

### ControllerBooter

#### Description

Discovers and binds Controller Classes using `app.controller()`.

#### Options

The options for this can be passed via `BootOptions` when calling
`app.boot(options: BootOptions)`.

The options for this are passed in a `controllers` object on `BootOptions`.

Available options on the `controllers` object on `BootOptions` are as follows:

| Options      | Type                 | Default              | Description                                                                                                  |
| ------------ | -------------------- | -------------------- | ------------------------------------------------------------------------------------------------------------ |
| `dirs`       | `string \| string[]` | `['controllers']`    | Paths relative to projectRoot to look in for Controller artifacts                                            |
| `extensions` | `string \| string[]` | `['.controller.js']` | File extensions to match for Controller artifacts                                                            |
| `nested`     | `boolean`            | `true`               | Look in nested directories in `dirs` for Controller artifacts                                                |
| `glob`       | `string`             |                      | A `glob` pattern string. This takes precedence over above 3 options (which are used to make a glob pattern). |

### RepositoryBooter

#### Description

Discovers and binds Repository Classes using `app.repository()` (Application
must use `RepositoryMixin` from `@loopback/repository`).

#### Options

The options for this can be passed via `BootOptions` when calling
`app.boot(options: BootOptions)`.

The options for this are passed in a `repositories` object on `BootOptions`.

Available options on the `repositories` object on `BootOptions` are as follows:

| Options      | Type                 | Default              | Description                                                                                                  |
| ------------ | -------------------- | -------------------- | ------------------------------------------------------------------------------------------------------------ |
| `dirs`       | `string \| string[]` | `['repositories']`   | Paths relative to projectRoot to look in for Repository artifacts                                            |
| `extensions` | `string \| string[]` | `['.repository.js']` | File extensions to match for Repository artifacts                                                            |
| `nested`     | `boolean`            | `true`               | Look in nested directories in `dirs` for Repository artifacts                                                |
| `glob`       | `string`             |                      | A `glob` pattern string. This takes precedence over above 3 options (which are used to make a glob pattern). |

### DataSourceBooter

#### Description

Discovers and binds DataSource Classes using `app.dataSource()` (Application
must use `RepositoryMixin` from `@loopback/repository`).

#### Options

The options for this can be passed via `BootOptions` when calling
`app.boot(options: BootOptions)`.

The options for this are passed in a `datasources` object on `BootOptions`.

Available options on the `datasources` object on `BootOptions` are as follows:

| Options      | Type                 | Default              | Description                                                                                                  |
| ------------ | -------------------- | -------------------- | ------------------------------------------------------------------------------------------------------------ |
| `dirs`       | `string \| string[]` | `['datasources']`    | Paths relative to projectRoot to look in for DataSource artifacts                                            |
| `extensions` | `string \| string[]` | `['.datasource.js']` | File extensions to match for DataSource artifacts                                                            |
| `nested`     | `boolean`            | `true`               | Look in nested directories in `dirs` for DataSource artifacts                                                |
| `glob`       | `string`             |                      | A `glob` pattern string. This takes precedence over above 3 options (which are used to make a glob pattern). |

### ServiceBooter

#### Description

Discovers and binds Service providers using `app.serviceProvider()` (Application
must use `ServiceMixin` from `@loopback/service-proxy`).

**IMPORTANT:** For a class to be recognized by `ServiceBooter` as a service
provider, its name must end with `Provider` suffix and its prototype must have a
`value()` method.

#### Options

The options for this can be passed via `BootOptions` when calling
`app.boot(options: BootOptions)`.

The options for this are passed in a `services` object on `BootOptions`.

Available options on the `services` object on `BootOptions` are as follows:

| Options      | Type                 | Default           | Description                                                                                                  |
| ------------ | -------------------- | ----------------- | ------------------------------------------------------------------------------------------------------------ |
| `dirs`       | `string \| string[]` | `['services']`    | Paths relative to projectRoot to look in for Service artifacts                                               |
| `extensions` | `string \| string[]` | `['.service.js']` | File extensions to match for Service artifacts                                                               |
| `nested`     | `boolean`            | `true`            | Look in nested directories in `dirs` for Service artifacts                                                   |
| `glob`       | `string`             |                   | A `glob` pattern string. This takes precedence over above 3 options (which are used to make a glob pattern). |

## Contributions

- [Guidelines](https://github.com/loopbackio/loopback-next/blob/master/docs/CONTRIBUTING.md)
- [Join the team](https://github.com/loopbackio/loopback-next/issues/110)

## Tests

Run `npm test` from the root folder.

## Contributors

See
[all contributors](https://github.com/loopbackio/loopback-next/graphs/contributors).

## License

MIT