examples/calculatorThe calculator.example microservice implement two endpoints, /arithmetic and /square in order to demonstrate functional handlers. These types of handlers automatically parse incoming requests (typically JSON over HTTP) and make it appear like a function is called. Functional endpoints are best called using the client that’s defined in the calculatorapi package. The hello.example discussed earlier is making use of this client.
The /arithmetic endpoint takes query arguments x and y of type integer, and one of four operators in the op argument: +, -, / and *. The response is a an echo of the input arguments and the result of the calculation. It is returned as JSON.
http://localhost:8080/calculator.example/arithmetic?x=5&op=*&y=-8 produces:
{"xEcho":5,"opEcho":"*","yEcho":-8,"result":-40}
The /square endpoint takes a single integer x and prints its square.
http://localhost:8080/calculator.example/square?x=55 produces:
{"xEcho":55,"result":3025}
If the arguments cannot be parsed, an error is returned.
http://localhost:8080/calculator.example/square?x=not-valid results in:
json: cannot unmarshal string into Go struct field .x of type int
The /distance endpoint demonstrates the use of a complex type Point. When an unknown type is used in any of the signatures in service.yaml, the code generator automatically defines an empty struct in a file of the same name (in this case point.go) in the API package:
// Point
type Point struct {
}
It can then be filled appropriately for its use case:
// Point is a 2D coordinate (X, Y)
type Point struct {
X float64 `json:"x,omitempty"`
Y float64 `json:"y,omitempty"`
}
Dot notation can be used in URL query arguments to denote values of nested fields. http://localhost:8080/calculator.example/distance?p1.x=0&p1.y=0&p2.x=3&p2.y=4 produces the result:
{"d":5}