jsonapi

A toolkit for building consistent json apis with ease.

Features:

• Custom request validation (we provide an adapter for github.com/xeipuuv/gojsonschema)
• Automatic parameter injection (we provide an adapter for github.com/gorilla/mux)

Check usage for examples.

Install

go get -u github.com/mnavarrocarter/jsonapi

Usage

You can wrap simple functions into a JsonHandler using jsonapi.Wrap(). This JsonHandler implements http.Handler so you can use it as you would use any handler.

package main

import (
	"context"
	"errors"
	"fmt"
	"github.com/mnavarrocarter/jsonapi"
	"net/http"
)

type GreetCmd struct {
	Name        string `json:"name"`
	ShouldPanic bool   `json:"shouldPanic"`
}

func Greet(_ context.Context, cmd *GreetCmd) (map[string]string, error) {
	if cmd.ShouldPanic {
		panic("something unexpected has happened")
	}

	if cmd.Name == "" {
		return nil, errors.New("you must provide a name")
	}

	return map[string]string{
		"message": fmt.Sprintf("Hello %s", cmd.Name),
	}, nil
}

func main() {
	handler := jsonapi.Wrap(Greet)

	err := http.ListenAndServe(":8000", handler)
	if err != nil {
		panic(err)
	}
}

Then you can invoke the handler and see the magic in action!

POST http://localhost:8000
Content-Type: application/json

{
  "name": "Matias"
}

---

HTTP/1.1 200 OK
Content-Type: application/json
Date: Mon, 25 Jul 2022 12:07:48 GMT
Content-Length: 27

{
  "message": "Hello Matias"
}

The json handler takes care of serializing the json and put it into the right struct, and then passing it into your function in the correct order. It can also inject any type that implements context.Context.

The handler is smart enough to check that it needs a body and if none is present will report back to the user:

GET http://localhost:8000

---

HTTP/1.1 400 Bad Request
Content-Type: application/json
Date: Mon, 25 Jul 2022 14:10:21 GMT
Content-Length: 81

{
  "status": 400,
  "kind": "Invalid Request",
  "details": "Request body cannot be empty"
}

Validation

You can instruct the handler to validate payloads by passing a json schema. This gives you valid structs in your handlers. The error reporting of the schema validation is consistent.

package main

import (
	"context"
	"errors"
	"fmt"
	"github.com/mnavarrocarter/jsonapi"
	"net/http"
	"strings"
)

type GreetCmd struct {
	Name        string `json:"name"`
	ShouldPanic bool   `json:"should_panic"`
}

func Greet(_ context.Context, cmd *GreetCmd) (map[string]string, error) {
	if cmd.ShouldPanic {
		panic("something unexpected has happened")
	}

	if cmd.Name == "" {
		return nil, errors.New("you must provide a name")
	}

	return map[string]string{
		"message": fmt.Sprintf("Hello %s", cmd.Name),
	}, nil
}

var schema = `{
    "type": "object",
    "properties": {
        "name": {
            "type": "string",
            "minLength": 2
        },
        "should_panic": {
            "type": "boolean"
        }
    }
}`

func main() {
	handler := jsonapi.Wrap(Greet, jsonapi.WithSchema(strings.NewReader(schema)))

	err := http.ListenAndServe(":8000", handler)
	if err != nil {
		panic(err)
	}
}

You can make your own validation logic by implementing jsonapi.RequestValidator.

Error Handling

Errors are handled properly by the handler's error handler.