LoopBack REST Connector

LoopBack REST connector allows Node.js application to interact with HTTP REST APIs using a template driven approach. It supports two different styles of API invocations:

Resource CRUD

If the REST APIs supports CRUD operations for resources, such as users or orders, you can simply bind the model to a REST endpoint that follows REST conventions.

The following methods are mixed into your model class:

• create: POST /users
• findById: GET /users/:id
• delete: DELETE /users/:id
• update: PUT /users/:id
• find: GET /users?limit=5&username=ray&order=email

Below is a simple example:

var ds = loopback.createDataSource({
    connector: require("loopback-connector-rest"),
    debug: false,
    baseURL: 'http://localhost:3000'
});

var User = ds.createModel('user', {
    name: String,
    bio: String,
    approved: Boolean,
    joinedAt: Date,
    age: Number
});

User.create(new User({name: 'Mary'}), function (err, user) {
    console.log(user);
});

User.find(function (err, user) {
    console.log(user);
});

User.findById(1, function (err, user) {
    console.log(err, user);
});

User.update(new User({id: 1, name: 'Raymond'}), function (err, user) {
    console.log(err, user);
});

Define a custom method using REST template

Imagine that you use browser or REST client to test drive a REST API, you will specify the following HTTP request properties:

• method: HTTP method
• url: The URL of the request
• headers: HTTP headers
• query: Query strings
• responsePath: JSONPath applied to the HTTP body

LoopBack REST connector allows you to define the API invocation as a json template. For example,

    template: {
            "method": "GET",
            "url": "http://maps.googleapis.com/maps/api/geocode/{format=json}",
            "headers": {
                "accepts": "application/json",
                "content-type": "application/json"
            },
            "query": {
                "address": "{street},{city},{zipcode}",
                "sensor": "{sensor=false}"
            },
            "responsePath": "$.results[0].geometry.location"
        }

The template variable syntax is as follows:

{name=defaultValue:type}

The variable is required if the name has a prefix of ! or ^

For example:

'{x=100:number}'
'{x:number}'
'{x}'
'{x=100}ABC{y}123'
'{!x}'
'{x=100}ABC{^y}123'

To use custom methods, you can configure the REST connector with the operations property, which is an array of objects that contain template and functions. The template property defines the API structure while the functions property defines JavaScript methods that takes the list of parameter names.

var loopback = require("loopback");

var ds = loopback.createDataSource({
    connector: require("loopback-connector-rest"),
    debug: false,
    operations: [
    {
        template: {
            "method": "GET",
            "url": "http://maps.googleapis.com/maps/api/geocode/{format=json}",
            "headers": {
                "accepts": "application/json",
                "content-type": "application/json"
            },
            "query": {
                "address": "{street},{city},{zipcode}",
                "sensor": "{sensor=false}"
            },
            "responsePath": "$.results[0].geometry.location"
        },
        functions: {
           "geocode": ["street", "city", "zipcode"]
        }
    }
]});

Now you can invoke the geocode API as follows:

Model.geocode('107 S B St', 'San Mateo', '94401', processResponse);

By default, LoopBack REST connector also provides an 'invoke' method to call the REST API with an object of parameters, for example:

Model.invoke({street: '107 S B St', city: 'San Mateo', zipcode: '94401'}, processResponse);