Simple Web API Server in Golang (1)

To be an better Gopher, get your hands dirty. Topcoder offered a serials of challenges for learning Golang.

In this blog, I tried to implement "Go Learning Challenge - Simple Web-API Server"[1].

What's used in this challenge ? Following aspects and packages will be covered in this challenge

How to create a HTTP server: net/http

How to create routers (handlers for different URLs): regex + url

How to write HTTP responses: net/http

How to load JSON config: json + io/ioutil

How to parse URL query string: url

How to encode data in sha256/base64: sha256/base64 + strings

How to write tests in Golang: testing

How to parse command line arguments: flag

How to log: log

Configuration File example:

[
{
"domain": "topcoder.com",
"users": [
{
"username": "takumi",
"password": "ilovego"
},
{
"username": "teru",
"password": "ilovejava"
},
{
"username": "toshi",
"password": "iloveapex"
}
]
},
{
"domain": "appirio.com",
"users": [
{
"username": "jun",
"password": "ilovetopcoder"
},
{
"username": "narinder",
"password": "ilovesamurai"
},
{
"username": "chris",
"password": "ilovesushi"
}
]
}
]

config.go

package SimpleWebAPIServer

import (
"io/ioutil"
"encoding/json"
"errors"
)

type User struct {
UserName string `json:"username"`
Password string `json:"password"`
}

type Domain struct {
Name string `json:"domain"`
Users UserList `json:"users"`
}

type DomainWarehouse []Domain
type UserList []User

func ReadConfig(fn string) (DomainWarehouse, error) {
data, err := ioutil.ReadFile(fn)
if err != nil {
return nil, err
}
//fmt.Println(string(data))

var m DomainWarehouse
json.Unmarshal(data, &m)
return m, nil
}

func (dw DomainWarehouse) GetDomain(name string) (*Domain, error) {
for _, domain := range dw {
if domain.Name == name {
return &domain, nil
}
}
return nil, errors.New("Failed to find domain")
}

func (ul UserList) GetUser(username string) (*User, error) {
for _, user := range ul {
if user.UserName == username {
return &user, nil
}
}
return nil, errors.New("Failed to find user")
}

tests for config.go

package SimpleWebAPIServer

import (
"testing"
"fmt"
)

func TestReadConfig(t *testing.T) {
dw, err := ReadConfig("./users.json")
if err != nil {
fmt.Println(err)
t.Error("Failed to read config")
}
if dw == nil || len(dw) != 2 {
t.Error("Failed to unmarshal json objects")
}

if dw[0].Name != "topcoder.com" || len(dw[0].Users) != 3 {
t.Error("Incorrect value")
}
}

func TestGetDomain(t *testing.T) {
dw, err := ReadConfig("./users.json")
if err != nil {
fmt.Println(err)
t.Error("Failed to read config")
}
domain, err := dw.GetDomain("topcoder.com")
if err != nil {
fmt.Println(err)
t.Error("Failed to get domain")
}
if domain.Name != "topcoder.com" || len(domain.Users) != 3 {
t.Error("Incorrect value")
}
}

func TestGetUser(t *testing.T) {
dw, err := ReadConfig("./users.json")
if err != nil {
fmt.Println(err)
t.Error("Failed to read config")
}
domain, err := dw.GetDomain("topcoder.com")
if err != nil {
fmt.Println(err)
t.Error("Failed to get domain")
}
if domain.Name != "topcoder.com" || len(domain.Users) != 3 {
t.Error("Incorrect value")
}

ul := domain.Users
u, err := ul.GetUser("takumi")
if err != nil {
t.Error("Failed to get user")
}
if u.UserName != "takumi" || u.Password != "ilovego" {
t.Error("Invalid user values")
}
}

After implementing this simple web api server, I got better understanding of Golang syntax and Web API stuffs. For more Web API server challenges, go to [3] about OAuth2.

[1] topcoder : http://www.topcoder.com/challenge-details/30046011/?type=develop&noncache=true

[2] git : https://coding.net/u/huys03/p/SimpleWebAPIServer/git

[3] next challenge: http://www.topcoder.com/challenge-details/30046224/?type=develop