LoopBack Boot

LoopBack Boot is a convention-based bootstrapper for LoopBack applications.

For full documentation, see the official StrongLoop documentation:

Installation

npm install loopback-boot

Usage

var loopback = require('loopback');
var boot = require('loopback-boot');

var app = loopback();
boot(app, __dirname);

app.use(loopback.rest());
app.listen();

See API docs for complete API reference.

Versions

The version range 1.x is backwards compatible with app.boot provided by LoopBack 1.x versions and the project layout scaffolded by slc lb project up to slc version 2.5.

The version range 2.x supports the new project layout as scaffolded by yo loopback.

This document describes the configuration conventions of the 2.x versions. See Migrating from 1.x to 2.x for step-by-step instructions on how to upgrade existing projects.

Configurations and conventions

The bootstrapping process takes care of the following tasks:

  • Configuration of data-sources.
  • Definition of custom Models
  • Configuration of models, attaching models to data-sources.
  • Configuration of app settings like host, port or restApiRoot.
  • Running additional boot scripts, so that the custom setup code can be kept in multiple small files as opposed to keeping everything in the main app file.

Below is the typical project layout. See the following sections for description of the project files.

project/
  app.js
  config.json
  datasources.json
  models.json
  models/
  boot/

App settings

The settings are loaded from the file config.json in the project root directory and can be accessed via app.get('option-name') from the code.

Additionally, the following files can provide values to override config.json:

  • config.local.js or config.local.json
  • config.{env}.js or config.{env}.json, where {env} is the value of NODE_ENV (typically development or production)

NOTE: The additional files can override the top-level keys with value-types (strings, numbers) only. Nested objects and arrays are not supported at the moment.

Example settings

config.json

{
  "host": "localhost",
  "port": 3000,
  "restApiRoot": "/api"
}

config.production.js

module.exports = {
  host: process.env.CUSTOM_HOST,
  port: process.env.CUSTOM_PORT
};

Data sources

The configuration of data sources is loaded from the file datasources.json in the project root directory, the data sources can be accessed via app.datasources['datasource-name'] from the code.

Additionally, the following files can provide values to override datasources.json:

  • datasources.local.js or datasources.local.json
  • datasources.{env}.js or datasources.{env}.json, where {env} is the value of NODE_ENV (typically development or production)

NOTE: The additional files can override the top-level data-source options with value-types (strings, numbers) only. Nested objects and arrays are not supported at the moment.

Example data sources

datasources.json

{
  // the key is the datasource name
  // the value is the config object to pass to
  //   app.dataSource(name, config).
  db: {
    connector: 'memory'
  }
}

datasources.production.json

{
  db: {
    connector: 'mongodb',
    database: 'myapp',
    user: 'myapp',
    password: 'secret'
  }
}

Models: definition

Custom models are defined using JSON files in models/ directory, one JSON file per model.

Example models

The following are example JSON files for two Model definitions: Dealership and Location.

models/dealership.json

{
  // the model name
  "name": "Dealership",
  // the options passed to Model.extend(name, properties, options)
  "options": {
    "relations": {
      "cars": {
        "type": "hasMany",
        "model": "Car",
        "foreignKey": "dealerId"
      }
    }
  },
  // the properties passed to Model.extend(name, properties, options)
  "properties": {
    "id": {"id": true},
    "name": "String",
    "zip": "Number",
    "address": "String"
  }
}

models/car.json

{
  "name": "Car",
  // options can be specified at the top level too
  "relations": {
    "dealer": {
      "type": "belongsTo",
      "model": "Dealership",
      "foreignKey": "dealerId"
    },
  }
  "properties": {
    "id": {
      "type": "String",
      "required": true,
      "id": true
    },
    "make": {
      "type": "String",
      "required": true
    },
    "model": {
      "type": "String",
      "required": true
    }
  }
}

Adding custom methods to models

The models created from JSON files come with the set of built-in methods like find and create. To implement your custom methods, you should create a javascript file in models/ directory with the same base-name as the JSON file containing model definition (e.g. models/car.js for models/car.json) and define the methods there.

Example:

models/car.js

// Car is the model constructor
// Base is the parent model (e.g. loopback.PersistedModel)
module.exports = function(Car, Base) {
  // Define a static method
  Car.customMethod = function(cb) {
    // do some work
    cb();
  };

  // Define an instance (prototype) method
  Car.prototype.honk = function(duration, cb) {
    // make some noise for `duration` seconds
    cb();
  };

  // Provide a custom setup method
  Car.setup = function() {
    Base.setup.call(this);

    // configure validations,
    // configure remoting for methods, etc.
  };
};

Models: configuration

Before the models can be used in a loopback application, they have to be configured - attached to a data-source, exposed via the REST API, and so on.

The configuration is described in the file models.json:

{
  // the key is the model name
  "Dealership": {
    // a reference, by name, to a dataSource definition
    "dataSource": "my-db"
  },
  "Car": {
    "dataSource": "my-db",
    // do not expose Car over the REST API
    "public": false
  }
}

The bootstrapper will automatically load definition of every custom model configured in models.json. By default, the definition files are loaded from models/ subdirectory. However, it is possible to specify a different location (or even multiple locations) via _meta.sources:

{
  "_meta": {
    "sources": [
      // all paths are relative to models.json
      "./models"
      "./node_modules/foobar/models"
    ]
  },
  // use the `FooBar` model from the `foobar` module
  "FooBar": {
    "dataSource": "db"
  }
}

Boot scripts

When the data sources and models are configured, the bootstrapper invokes all scripts in the boot/ folder. The scripts are sorted lexicographically ingoring case.

Example boot script

boot/authentication.js

module.exports = function(app) {
  app.enableAuth();
};

Running in a browser

The bootstrap process is implemented in two steps that can be called independently.

Build

The first step loads all configuration files, merges values from additional config files like app.local.js and produces a set of instructions that can be used to boot the application.

These instructions must be included in the browser bundle together with all configuration scripts from models/ and boot/.

Don't worry, you don't have to understand these details. Just call boot.compileToBrowserify, it will take care of everything for you.

build file (Gruntfile.js, gulpfile.js)

var browserify = require('browserify');
var boot = require('loopback-boot');

var b = browserify({
  basedir: appDir,
});

// add the main application file
b.require('./browser-app.js', { expose: 'loopback-app' });

// add boot instructions
boot.compileToBrowserify(appDir, b);

// create the bundle
var out = fs.createWriteStream('browser-bundle.js');
b.bundle().pipe(out);
// handle out.on('error') and out.on('close')

Run

In the browser, the main application file should call loopback-boot to setup the loopback application by executing the instructions contained in the browser bundle:

browser-app.js

var loopback = require('loopback');
var boot = require('loopback-boot');

var app = module.exports = loopback();
boot(app);

The app object created above can be accessed via require('loopback-app'), where loopback-app is the identifier used for the main app file in the browserify build shown above.

Here is a simple example demonstrating the concept:

index.html

<script src="app.bundle.js"></script>
<script>
var app = require('loopback-app');
var User = app.models.User;

User.login(
  { email: 'test@example.com', password: '12345' },
  function(err, res) {
    if (err) {
      console.error('Login failed: ', err);
    } else {
      console.log('Logged in.');
    }
  }
);
</script>

API

bootLoopBackApp(app, [options])

Initialize an application from an options object or a set of JSON and JavaScript files.

NOTE: This module is primarily intended for use with LoopBack 2.0. It does work with LoopBack 1.x applications, but none of the LoopBack 1.x examples or generated code (scaffolding) use it.

This function takes an optional argument that is either a string or an object.

If the argument is a string, then it sets the application root directory based on the string value. Then it:

  1. Creates DataSources from the datasources.json file in the application root directory.

  2. Configures Models from the models.json file in the application root directory.

If the argument is an object, then it looks for models, dataSources, and appRootDir properties of the object. If the object has no appRootDir property then it sets the current working directory as the application root directory. Then it:

  1. Creates DataSources from the options.dataSources object.

  2. Configures Models from the options.models object.

In both cases, the function loads JavaScript files in the /boot subdirectory of the application root directory with require().

NOTE: The version 2.0 of loopback-boot changed the way how models are created. The models.json file contains only configuration options like dataSource and extra relations. To define a model, create a per-model JSON file in models/ directory.

NOTE: Mixing bootLoopBackApp(app, bootConfig) and app.model(name, modelConfig) in multiple files may result in models being undefined due to race conditions. To avoid this when using bootLoopBackApp() make sure all models are passed as part of the models definition.

Throws an error if the config object is not valid or if boot fails.

Arguments
Name Type Description
app

LoopBack application created by loopback().
options String or Object

Boot options; If String, this is the application root directory; if object, has below properties.
options
Name Type Description
[appRootDir] String

Directory to use when loading JSON and JavaScript files. Defaults to the current directory (process.cwd()).
[models] Object

Object containing Model configurations.
[dataSources] Object

Object containing DataSource definitions.
[modelsRootDir] String

Directory to use when loading models.json. Defaults to appRootDir.
[dsRootDir] String

Directory to use when loading datasources.json. Defaults to appRootDir.
[env] String

Environment type, defaults to process.env.NODE_ENV or development. Common values are development, staging and production; however the applications are free to use any names.
[modelSources] Array.<String>

List of directories where to look for files containing model definitions.

boot.compileToBrowserify(options, bundler)

Compile boot instructions and add them to a browserify bundler.

Arguments
Name Type Description
options Object or String

as described in bootLoopBackApp above.
bundler Object

A browserify bundler created by browserify().

bootBrowserApp(app)

The browser version of bootLoopBackApp.

When loopback-boot is loaded in browser, the module exports this function instead of bootLoopBackApp.

The function expects the boot instructions to be included in the browser bundle, see boot.compileToBrowserify.

Arguments
Name Type Description
app Object

The loopback app to boot, as returned by loopback().

Migrating from 1.x to 2.x

Starting point: a sample 1.x project

models.json

{
  "car": {
    "properties": {
      "color": "string",
    },
    "dataSource": "db"
  }
}

models/car.js

var app = require('../app');
var Car = app.models.Car;

Car.prototype.honk = function(duration, cb) {
  // make some noise for `duration` seconds
  cb();
};

app.js

var loopback = require('loopback');
var boot = require('loopback-boot');
var app = loopback();
boot(app, __dirname);

App settings

The files with applications settings were renamed from app.* to config.*. Rename the following files to upgrade a 1.x project for loopback-boot 2.x:

  • app.json to config.json
  • app.local.json to config.local.json
  • app.local.js to config.local.js
  • etc.

Data sources

The configuration of data sources remains the same in both 1.x and 2.x versions.

Models

The 2.x version of loopback-boot no longer creates Models, it's up to the developer to create them before booting the app.

The folder models/ has a different semantincs in 2.x than in 1.x. Instead of extending Models already defined by app.boot and models.json, it provides a set of Model definitions that do not depend on any application that may use them.

Perform the following steps to update a 1.x project for loopback-boot 2.x. All code samples are referring to the sample project described above.

  1. Move all Model-definition metadata from models.json to new per-model json files in models/ directory.

    models/car.json

    {
  "name": "car",
  "properties": {
    "color": "string",
  }
}

    models.json

    {
  "car": {
    "dataSource": "db"
  }
}

  2. Change per-model javascript files to export a function that adds custom methods to the model class.

    models/car.js

    module.exports = function(Car, Base) {
  Car.prototype.honk = function(duration, cb) {
    // make some noise for `duration` seconds
    cb();
  };
};

  3. If your model definitions are not in ./models, then add an entry to models.json to specify the paths where to look for model definitions.

    models.json

    {
  "_meta": {
    "sources": ["./custom/path/to/models"]
  },
  "Car": {
    "dataSource": "db"
  }
}

Attaching built-in models

Models provided by LoopBack, such as User or Role, are no longer automatically attached to default data-sources. The data-source configuration entry defaultForType is silently ignored.

You have to explicitly configure all built-in models used by your application in the models.json file.

{
  "Role": { "dataSource": "db" }
}