loopback-example-database

A brief tutorial on using the LoopBack PostgreSQL connector.Note: This page was generated from the loopback-example-database/README.md.

loopback-example-database

A tutorial for basic database related features.

Overview

Topics covered

Data sources
- Creating
- Configuring
Models
- Creating
Automigration
Discovery

Database specific tutorials

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

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

For example, to view the PostgreSQL example:

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

Prerequisites

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

Node
LoopBack CLI tools; see lb

Running the example

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

Tutorial - PostgreSQL

1. Create a new LoopBack app

App info

Name: loopback-example-database
Dir to contain the project: loopback-example-database

lb app loopback-example-database
... # follow the prompts

2. Install the LoopBack PostgreSQL connector

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

3. Create a data source

Data source info

Data source name: accountDS
Select the connector for accountDS: PostgreSQL

lb datasource accountDS
... # follow the prompts

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

4. Configure the data source

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

{
  ...
  "accountDS": {
    "name": "accountDS",
    "connector": "postgresql",
    "host": "demo.strongloop.com",
    "port": 5432,
    "database": "demo",
    "username": "demo",
    "password": "L00pBack"
  }
}

Feel free to use your own local PostgreSQL instance. Simply change the configsabove to match your own.

5. Create a new model

Model Info

Model name: Account
Attach Account to: accountDS (postgresql)
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

lb model Account
... # follow the prompts

6. Create the collection with sample data - Automigration

With the account model configured, we can generate the correspondingPostgreSQL table using the info from the Account metadata in common/models/account.jsonvia 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. Ifthe collection already exists, it will be destroyed and it’s data will bedeleted. If you want to keep this data, use autoupdate instead.

You should see:

Created: { email: 'john.doe@ibm.com',
  createdAt: Fri Oct 23 2015 17:14:03 GMT-0700 (PDT),
  lastModifiedAt: Fri Oct 23 2015 17:14:03 GMT-0700 (PDT),
  id: 1 }
Created: { email: 'jane.doe@ibm.com',
  createdAt: Fri Oct 23 2015 17:14:03 GMT-0700 (PDT),
  lastModifiedAt: Fri Oct 23 2015 17:14:03 GMT-0700 (PDT),
  id: 2 }

7. View data using the explorer

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

node .

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

GET /Accounts
Try it out!You should see:

[
  {
    "email": "john.doe@ibm.com",
    "createdAt": "2015-10-24T00:14:03.567Z",
    "lastModifiedAt": "2015-10-24T00:14:03.567Z",
    "id": 1
  },
  {
    "email": "jane.doe@ibm.com",
    "createdAt": "2015-10-24T00:14:03.567Z",
    "lastModifiedAt": "2015-10-24T00:14:03.567Z",
    "id": 2
  }
]

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

8. Add a script to perform discover the database schema

Discoveryis the process of reverse engineering a LoopBack model from an existingdatabase schema.

Create a script name discover-schema.js. Then run this script todiscover the schema from the existing Account table:

node bin/discover-schema

You should see:

{
  "name": "Account",
  "options": {
    "idInjection": false,
    "postgresql": {
      "schema": "public",
      "table": "account"
    }
  },
  "properties": {
    "email": {
      "type": "String",
      "required": false,
      "length": 1024,
      "precision": null,
      "scale": null,
      "postgresql": {
        "columnName": "email",
        "dataType": "character varying",
        "dataLength": 1024,
        "dataPrecision": null,
        "dataScale": null,
        "nullable": "YES"
      }
    },
    "createdat": {
      "type": "String",
      "required": false,
      "length": null,
      "precision": null,
      "scale": null,
      "postgresql": {
        "columnName": "createdat",
        "dataType": "timestamp with time zone",
        "dataLength": null,
        "dataPrecision": null,
        "dataScale": null,
        "nullable": "YES"
      }
    },
    "lastmodifiedat": {
      "type": "String",
      "required": false,
      "length": null,
      "precision": null,
      "scale": null,
      "postgresql": {
        "columnName": "lastmodifiedat",
        "dataType": "timestamp with time zone",
        "dataLength": null,
        "dataPrecision": null,
        "dataScale": null,
        "nullable": "YES"
      }
    },
    "id": {
      "type": "Number",
      "required": true,
      "length": null,
      "precision": 32,
      "scale": 0,
      "id": 1,
      "postgresql": {
        "columnName": "id",
        "dataType": "integer",
        "dataLength": null,
        "dataPrecision": 32,
        "dataScale": 0,
        "nullable": "NO"
      }
    }
  }
}

9. Add a script to discover and build models

When retrieving the scheme is not enough, you can discover and build LoopBackmodels in one step.

Create a script named discover-and-build-models.js.Then run:

node bin/discover-and-build-models

You should see:

[ { email: 'john.doe@ibm.com',
    createdat: Fri Oct 23 2015 17:39:50 GMT-0700 (PDT),
    lastmodifiedat: Fri Oct 23 2015 17:39:50 GMT-0700 (PDT),
    id: 1 },
  { email: 'jane.doe@ibm.com',
    createdat: Fri Oct 23 2015 17:39:50 GMT-0700 (PDT),
    lastmodifiedat: Fri Oct 23 2015 17:39:50 GMT-0700 (PDT),
    id: 2 } ]