BSON JSON id vs _id - mongodb

Question

I am creating simple REST API using MongoDB and golang as a driver.
I was able to create POST request which can be found here:
terminal output.
However, when creating GET request, i always need to get it by bson _id. Would someone be able to let me know how to retrieve from json id not bson _id from golang script. If this is not possible, I would appreciate if someone let me know how to convert id to _id.
models/user.go
package models
import (
"gopkg.in/mgo.v2/bson"
)
type User struct {
Id bson.ObjectId `json:"id" bson: "_id"`
Name string `json:"name" bson: "name"`
Gender string `json:"gender" bson: "gender"`
Age int `json:"age" bson: "age"`
}
controllers/user.go file
type UserController struct {
session *mgo.Session}
func httpResponse(w http.ResponseWriter, jsonOut []byte, code int) {
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(code)
fmt.Fprintf(w, "%s", jsonOut)
}
func NewUserCOntroller(s *mgo.Session) *UserController {
// return the address of UserController
return &UserController{s}
}
func (uc UserController) GetUser(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
id := p.ByName("id")
if !bson.IsObjectIdHex(id) {
w.WriteHeader(http.StatusNotFound)
}
// oid is something you use in mongo
oid := bson.ObjectIdHex(id)
u := models.User{}
if err := uc.session.DB("mongolang").C("users").FindId(oid).One(&u); err != nil {
w.WriteHeader(404)
return
}
uj, err := json.Marshal(u)
if err != nil {
fmt.Println(err)
}
httpResponse(w, uj, http.StatusOK)
}
func (uc UserController) CreateUser(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
// its empty for now
u := models.User{}
json.NewDecoder(r.Body).Decode(&u)
u.Id = bson.NewObjectId()
uc.session.DB("mongolang").C("users").Insert(u)
jsonOut, _ := json.Marshal(u)
httpResponse(w, jsonOut, http.StatusOK)
fmt.Println("Response:", string(jsonOut), " 201 OK")
}
main.go
package main
import (
"net/http"
"github.com/julienschmidt/httprouter"
"gopkg.in/mgo.v2"
"mongo-golang/controllers"
)
func main() {
// create new instance
r := httprouter.New()
// new session
uc := controllers.NewUserCOntroller(getSession())
r.GET("/user/:id", uc.GetUser)
r.POST("/user", uc.CreateUser)
r.DELETE("/user/:id", uc.DeleteUser)
http.ListenAndServe("localhost:9000", r)
}
func getSession() *mgo.Session {
// get session and connect with mongo
s, err := mgo.Dial("mongodb://localhost")
if err != nil {
panic(err)
}
return s
}

Answer 1

Would someone be able to let me know how to retrieve from json id not bson _id from golang script.
You can do that only if you save bson Id as a Hex string in the additional field in an object, but don't do that. That is unnecessary and you won't get anything.
If this is not possible, I would appreciate if someone let me know how to convert id to _id.
There are two functions that converting bson ObjectID to string and string to bson ObjectID
for id to _id, you already use that function in your code:
oid := bson.ObjectIdHex(id)
bson.ObjectIdHex() convert hex representation of objectID to bson.objectID. Hex representation is what you would see in JSON output.
After you invoke that function you get bson.ObjetID. There is a method .Hex() that can get you Hex (text/json) representation of that object.
oid := bson.ObjectIdHex(id)
json_represenation_of_bson_object_id = oid.Hex()
Also, you use the old mongo driver, a new driver written and maintained by MongoDB is what you should use:
https://github.com/mongodb/mongo-go-driver