Page Contents

loopback-example-database

A tutorial for basic database related features.

Overview

Topics covered

  • Data sources
    • Creating
    • Configuring
  • Models
    • Creating
  • Automigration
  • Instance introspection (Discovery)

Database specific tutorials

Database specific tutorials are on separate branches. The master branch contains the tutorial for MongoDB.

Branch Connector
master MongoDB
mssql Microsoft SQL Server
mysql MySQL
oracle Oracle
postgresql PostgreSQL

For example, to view the MySQL example:

git clone https://github.com/strongloop/loopback-example-database
cd loopback-example-database
git checkout mysql

Prerequisites

Before starting this tutorial, make sure you have the following installed:

Running the example

git clone https://github.com/strongloop/loopback-example-database
cd loopback-example-database
npm install
npm start

Tutorial - MongoDB

1. Create a new LoopBack app

App info

  • Name: loopback-example-database
  • Dir to contain the project: loopback-example-database
slc loopback loopback-example-database
... # follow the prompts

2. Install the LoopBack MongoDB connector

cd loopback-example-database
npm install --save loopback-connector-mongodb

3. Create a data source

Data source info

  • Data source name: accountDS
  • Select the connector for accountDS: MongoDB
slc loopback:datasource accountDS
... # follow the prompts

This creates a new data source named accountDS that uses the MongoDB connector.

4. Configure the data source

For the purposes of this example, we will use a preconfigured StrongLoop MongoDB server. Edit server/datasources.json to set the MongoDB configs:

{
  ...
  "accountDS": {
    "name": "accountDS",
    "connector": "mongodb",
    "host": "demo.strongloop.com",
    "port": 27017,
    "database": "demo",
    "username": "demo",
    "password": "L00pBack"
  }
}

Feel free to use your own local MongoDB instance. Simply change the configs above to match your own.

5. Create a new model

Model Info

  • Model name: Account
  • Attach Account to: accountDS (mongodb)
  • Base class: PersistedModel
  • Expose via REST: Yes
  • Custom plural form: *Leave blank*
  • Properties:
    • email
      • String
      • Not required
    • createdAt
      • Date
      • Not required
    • lastModifiedAt
      • Date
      • Not required
slc loopback:model Account
... # follow the prompts

6. Create the collection with sample data - Automigration

With the account model configured, we can generate the corresponding MongoDB collection using the info from the Account metadata in common/models/account.json via auto-migration.

Start by creating a dir to store general-purpose scripts:

mkdir bin

Inside that dir, create a script named automigrate.js. To create the Account collection and create two sample accounts, run:

node bin/automigrate.js

WARNING

The automigrate function creates a new collection if it doesn’t exist. If the collection already exists, it will be destroyed and it’s data will be deleted. If you want to keep this data, use autoupdate instead.

You should see:

Created: { email: 'baz@qux.com',
  createdAt: Thu Oct 22 2015 17:58:09 GMT-0700 (PDT),
  lastModifiedAt: Thu Oct 22 2015 17:58:09 GMT-0700 (PDT),
  id: 562986213ea33440575c6588 }
Created: { email: 'foo@bar.com',
  createdAt: Thu Oct 22 2015 17:58:09 GMT-0700 (PDT),
  lastModifiedAt: Thu Oct 22 2015 17:58:09 GMT-0700 (PDT),
  id: 562986213ea33440575c6587 }

If you are using Node 4, it is safe to ignore Swagger: skipping unknown type "ObjectId". This warning will be addressed in a future update.

7. View data using the explorer

Projects scaffolded via slc loopback come with loopback-component-explorer preconfigured. From the project root, start the server:

node .

Then to view the existing account data, browse to localhost:3000/explorer and click:

  • GET /Accounts
  • Try it out!

You should see:

[
  {
    "email": "foo@bar.com",
    "createdAt": "2015-10-23T00:58:09.280Z",
    "lastModifiedAt": "2015-10-23T00:58:09.280Z",
    "id": "562986213ea33440575c6587"
  },
  {
    "email": "baz@qux.com",
    "createdAt": "2015-10-23T00:58:09.280Z",
    "lastModifiedAt": "2015-10-23T00:58:09.280Z",
    "id": "562986213ea33440575c6588"
  }
]

Try out some of the other endpoints to get a feel for how explorer works.

8. Add a script to perform instance instrospection (Discovery)

Discovery is the process of reverse engineering a LoopBack model from an existing database schema.

The LoopBack MongoDB connector does not support discovery. However, you can use instance instrospection, which creates a LoopBack model from an existing JavaScript object.

To do this, create a script named instance-introspections.js in the bin dir. Then run:

node bin/instance-introspection

You should see:

Created: { email: 'bob.doe@ibm.com',
  createdAt: Thu Oct 22 2015 19:38:20 GMT-0700 (PDT),
  lastModifiedAt: Thu Oct 22 2015 19:38:20 GMT-0700 (PDT),
  id: 56299d9d71c7f600719ca39f }

See the official docs for more info.

More LoopBack examples