HTTP client

Before an order goes to picking, every line is checked against the stock service over HTTP. The stock service runs inside this same example, so there is nothing else to start: the first two routes are a trimmed copy of stock-api, the third is the client.

What you will see

INFO ... http-client.camel.yaml:112 : ORD-1001: CAMEL-TSHIRT x 2, 120 in stock, ok
INFO ... http-client.camel.yaml:112 : ORD-1001: CAMEL-MUG x 1, 42 in stock, ok
INFO ... http-client.camel.yaml:112 : ORD-1002: CAMEL-MUG x 3, 42 in stock, ok
INFO ... http-client.camel.yaml:112 : ORD-1003: CAMEL-TSHIRT x 1, 120 in stock, ok
INFO ... http-client.camel.yaml:116 : ORD-1003: CAMEL-CAP x 1, only 0 in stock, back-order
INFO ... http-client.camel.yaml:112 : ORD-1003: CAMEL-MUG x 2, 42 in stock, ok

Install Camel CLI

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

Run it

camel run *

The three orders in orders/ are read once each (noop: true leaves the files in place), so the run can be repeated. The stock levels are in stock.json.

How it works

• The client splits each order into lines, as order-lines does, and calls toD with http://localhost:8080/stock/${variable.sku}: toD because the URI is built per message.
• The SKU, the quantity and the order id are kept in variables, not headers: headers travel on the HTTP request, and a header named sku would collide with the {sku} path parameter on the server side. Variables stay in the route.
• The body is set to null before the call: a GET has no body, and the order line would otherwise be sent. The response replaces the body, which is why the line was saved in variables first.
• throwExceptionOnFailure=false turns a 404 into a normal response with CamelHttpResponseCode set, so the choice can log it instead of the error handler.

Build it step by step

1. Start from stock-api and add a file route on orders that logs each order.
2. Split the lines and call http://localhost:8080/stock/CAMEL-MUG with a fixed SKU; log the response body.
3. Build the URI from the line with toD and a variable; notice the body is gone after the call.
4. Add throwExceptionOnFailure=false and the choice on the response code and the quantity.

Try changing

• Remove throwExceptionOnFailure=false and add a SKU that does not exist to an order: the 404 becomes an HttpOperationFailedException handled by the error handler.
• Call a public API instead, https://api.github.com/repos/apache/camel for example, and log ${body[stargazers_count]}.
• Set camel.server.port to another port and update the URI to match.

Integration testing

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

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

The test starts the routes and verifies the ok and back-order lines.

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!