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If you have any cache run before installation
npm cache clean -f

Install the CLI globally by running

npm i -g @loopback/cli

Create a new project

lb4 app

? Project name: getting-started
? Project description: Getting started tutorial
? Project root directory: (getting-started)
? Application class name: StarterApplication
? Select features to enable in the project:
❯◉ Enable tslint
◉ Enable prettier
◉ Enable mocha
◉ Enable loopbackBuild
◉ Enable vscode
◉ Enable repositories
◉ Enable services

$ npm start

loopbackf4@1.0.0 prestart F:LB4online_loop
npm run build

loopbackf4@1.0.0 build F:LB4online_loop
lb-tsc es2017 --outDir dist

loopbackf4@1.0.0 start F:LB4online_loop
node .

Server is running at http://127.0.0.1:3000
Try http://127.0.0.1:3000/ping

Create Loopback4 datasource command

$ lb4 datasource

? Datasource name: postgresdbconnect

? Select the connector for postgresdbconnect: PostgreSQL (supported by StrongLoop)

? Connection String url to override other settings (eg: postgres://username:password@localhost/database): postgres://postgres:postgres@localhost/learndb
? host: 5432
? port: 5432
? user:
? password: [hidden]
? database: learndb
create srcdatasourcespostgresdbconnect.datasource.json
create srcdatasourcespostgresdbconnect.datasource.ts
npm WARN loopbackf4@1.0.0 No license field.

• loopback-connector-postgresql@3.5.0
  added 17 packages in 28.938s
  update srcdatasourcesindex.ts

Datasource postgresdbconnect was created in srcdatasources/

Create Controllers

$ lb4 controller
? Controller class name: login
? What kind of controller would you like to generate? Empty Controller
create srccontrollerslogin.controller.ts
update srccontrollersindex.ts

Controller login was created in srccontrollers/

lb4 Create a new LoopBack4 application

lb4 extension Create a new LoopBack4 extension

lb4 example Download one of LoopBack example projects

lb4 controller Add a new controller to a LoopBack 4 application

lb4 datasource Add a new datasource to a LoopBack 4 application

lb4 model Add a new model to a LoopBack 4 application Model generator
lb4 repository Add new repositories for selected model(s) to a LoopBack 4 application

lb4 service Add new service for a selected datasource to a LoopBack 4 application

lb4 openapi Generate controllers and models from OpenAPI specs

To open

http://localhost:3000/

To Check in swagger-ui

http://localhost:3000/swagger-ui

http://localhost:3000/openapi.json

Intigration with OAS GraphQL

Create one folder and Past Json file

Ref: http://v4.loopback.io/getting-started-oasgraph.html

The Command Line Interface (CLI) provides a convenient way to start a GraphQL server wrapping an API for a given OpenAPI Specification.

npm i -g oasgraph-cli

http://localhost:3000/openapi.json

If you use LoopBack, start your API server in the LoopBack project folder, and access the API's OAS at http://127.0.0.1:3000/openapi.json. Save the OAS to disk.

http://localhost:3002/graphql

npm start
Start GraphQL server
Once OASGraph is installed and the OAS is obtained, you can create and start the GraphQL server from the folder in which OASGraph is installed. The created GraphQL server is then accessible at http://127.0.0.1:3001/graphql.

oasgraph [port number|--save]
oasgraph filename.json 30002

Open this location
http://localhost:3002/graphql