Docs: how to use OpenAPI connector

[bajtos]

As a LoopBack 4 user connecting to a REST service with an OpenAPI description, I would like to leverage loopback-connector-openapi to build an easy-to-use service proxy for me. Unfortunately, there is very little information how to do that.

Acceptance Criteria

• Enhance Calling other APIs and web services to show how to use OpenAPI connector
• Update connector's README file to make it relevant for LB4 users.

Possible structure:

• In "Calling other APIs", provide short section covering the common path at high level and point users to the connector docs for more details.
• In connector's README, go deeper into OpenAPI-specific configuration and behavior.

[dhmlau]

@bajtos @raymondfeng , just wanna confirm with you the requirement of this task before starting to write anything.

If we want to call a third party REST API, say the PetStore, we would:

• step 1: Run lb4 openapi with the OpenAPI json, to create the models and controller
• step 2: Run lb4 datasource with the PetStore API url using REST connector
• step 3: Run lb4 service to create the service proxy with the above datasource
• step 4: Implement the methods in the controller generated in step 1 to call the service from step 3

Are they what the right steps? Thanks.

[raymondfeng]

lb4 openapi is to implement an OpenAPI spec. To access 3rd party REST service with OpenAPI spec, use lb4 datasource and lb4 service (with loopback-connector-openapi).

In the future, we should extend lb4 openapi --client option to generate client service proxies with strongly-typed interfaces and types. Contrast to lb4 openapi generating controller code, the client option should generate client proxy/stub instead.

[dhmlau]

I actually tried with lb4 datasource (with OpenAPI connector) and lb4 service.
The datasource json is:

  "name": "ds",
  "connector": "openapi",
  "spec": "http://petstore.swagger.io:8080/api/v3/openapi.json",
  "validate": false,
  "positional": false
}

and I ran into error:

Unhandled error in POST /pet: 500 Error: only absolute urls are supported

Any ideas?

[dhmlau]

Let me try again and create a repo if the problem still exists.

[dhmlau]

@raymondfeng, looks like the "absolute urls" error still exists.

This is my repo: https://github.com/dhmlau/openapi-test2

• there is one endpoint for addPet. Use the following requestBody:

{
  "id": 10,
  "name": "doggie",
  "category": {
    "id": 1,
    "name": "Dogs"
  },
  "photoUrls": [
    "string"
  ],
  "tags": [
    {
      "id": 0,
      "name": "string"
    }
  ],
  "status": "available"
}

Then you'll get an error something like:

Unhandled error in POST /pets: 500 Error: only absolute urls are supported
    at /Users/dhmlau/loopback4-example/openapi-test/node_modules/node-fetch/index.js:54:10
    at new Promise (<anonymous>)
    at new Fetch (/Users/dhmlau/loopback4-example/openapi-test/node_modules/node-fetch/index.js:49:9)
    at Object.Fetch (/Users/dhmlau/loopback4-example/openapi-test/node_modules/node-fetch/index.js:37:10)
    at Object.fetch (/Users/dhmlau/loopback4-example/openapi-test/node_modules/cross-fetch/fetch-node.js:11:20)
    at _callee$ (/Users/dhmlau/loopback4-example/openapi-test/node_modules/swagger-client/dist/index.js:581:86)

Thanks!

[dhmlau]

Still investigating. Got passed the above error, because it's expecting url in https://github.com/dhmlau/openapi-test2/blob/master/petstore.json#L18 to be in absolute path. But I got a 400 Bad Request error.

[dhmlau]

Got it working in https://github.com/dhmlau/openapi-test2.
Taking the petstore json, I need to modify this line:

  "servers": [{"url": "/api/v3"}],

to

  "servers": [{"url": "http://petstore.swagger.io:8080/api/v3/"}],

Otherwise, I will get the 500 Error: only absolute urls are supported error.