OpenAPI client

The picking desk reserves the stock for every order line by calling the stock API by contract: stock-api.json says which operations exist and how to call them, and the rest-openapi component turns an operationId into the HTTP request. The server is the openapi-server example, running in another terminal.

What you will see

INFO ... openapi-client.camel.yaml:63 : ORD-1001: reserved 2 x CAMEL-TSHIRT, 120 left on the shelf
INFO ... openapi-client.camel.yaml:63 : ORD-1001: reserved 1 x CAMEL-MUG, 42 left on the shelf
INFO ... openapi-client.camel.yaml:63 : ORD-1002: reserved 3 x CAMEL-MUG, 42 left on the shelf
INFO ... openapi-client.camel.yaml:63 : ORD-1003: reserved 1 x CAMEL-TSHIRT, 120 left on the shelf
WARN ... openapi-client.camel.yaml:13 : ORD-1003: CAMEL-CAP not reserved, the stock API answered 409: {"error": "only 0 CAMEL-CAP in stock, 1 wanted for ORD-1003"}
INFO ... openapi-client.camel.yaml:63 : ORD-1003: reserved 2 x CAMEL-MUG, 42 left on the shelf

Install Camel CLI

Install JBang and the Camel CLI as described in the root README; camel --version confirms the install.

Run it

Start the server first, in the openapi-server directory:

camel run *

Then, in this directory:

camel run *

The three orders in orders/ are read once each (noop: true leaves the files in place), so the run can be repeated. stock.api.url in application.properties says where the server is.

How it works

rest-openapi with specificationUri: stock-api.json and operationId: reserveStock is the call: the component reads the verb, the path and the parameters from the contract, so the route never spells out POST /api/stock/{sku}/reserve. host is the server; componentName: http picks the HTTP client to use.
The path parameter sku is taken from the header of the same name; the request body is the message body, built here as the JSON the contract's Reservation schema describes.
Client request validation is on (camel.component.rest-openapi.request-validation-enabled=true in application.properties): a call without a value for a path parameter, a required header or query parameter, or a required body is refused before it is sent, with a message that names what is missing, instead of going out with {sku} in the path.
The order id and SKU are also kept in variables for the log, since the response replaces the body and headers are sent on the wire, as the http-client example explains.
A 409 or 400 from the server is an HttpOperationFailedException; the onException logs its status code and response body and continues with the next line.

Build it step by step

A timer route that calls rest-openapi with operationId: getStock and a fixed sku header; log the body.
Read the orders, split the lines, and call reserveStock with the reservation as the body.
Keep the order id and SKU in variables and log the result.
Add the onException and see the cap's 409 handled instead of failing the order.

Try changing

Remove the sku header before the call: the validation refuses it with “Path parameter ‘sku’ is required but none found” before any HTTP call. Turn the validation off in application.properties and the request goes out with {sku} in the path and gets a 404.
Point stock.api.url at a server that is not running and watch the connection error reach the error handler.
Replace the contract's server with a public one, https://petstore3.swagger.io/api/v3/openapi.json, and call getPetById.

Integration testing

The example comes with a test in the Citrus YAML DSL, test/openapi-client.citrus.it.yaml, which the Camel CLI runs:

camel test run test/openapi-client.citrus.it.yaml

The test starts the openapi-server example and this client, and verifies the reservations and the 409.

Help and contributions

If you hit any problem using Camel or have some feedback, then please let us know.

We also love contributors, so get involved :-)

The Camel riders!