When the service is invoked with a GraphQL query specifying the input name, the service will respond with a greetings message including the input name specified in the GraphQL query received via an HTTP POST. The sample implementation shows a simple GraphQL endpoint that has a single field (i.e. "greeting") with an input value (i.e. "name") in the root Query type, which returns a string (i.e. greetings message) or an error. The input parameters in the resource function becomes the input values of the corresponding GraphQL field. In this GraphQL schema, the greeting field of Query type has a name input value, which accepts string values.
Run the Ballerina project created by the service sample by executing bal run from the root.
Once successfully executed, Listener will be started at port 8090. Then you need to invoke the service using the following curl command
$ curl -X POST -H "Content-type: application/json" -d '{ "query": "{ greeting(name: \"John\") }" }' 'http://localhost:8090'
The GraphQL query used: { greeting(name: "John") }. Now service will be invoked and returns the greetings message as
{"data":{"greeting":"Hello, John"}}