Golang: Using reflection to abstract web handlers on models in

routes_api.go

package routes

import (
  "github.com/theterg/BOH-web/models"
  "github.com/bmizerany/pat"
  "net/http"
  "strconv"
  "encoding/json"
  "reflect"
)

// Global vars for this package:
//var db *gorm.DB
//var generate *render.Render
//var sitevars *SiteVars

func Add_API_routes(prefix string, mux *pat.PatternServeMux) {
  mux.Get(prefix+"/employees", http.HandlerFunc(employee_list))
  mux.Get(prefix+"/employee/:id", http.HandlerFunc(employee_get))
  mux.Del(prefix+"/employee/:id", http.HandlerFunc(employee_delete))
  mux.Put(prefix+"/employees", http.HandlerFunc(employee_create))
  mux.Put(prefix+"/employee/:id", http.HandlerFunc(employee_update))
}

func employee_list(w http.ResponseWriter, req *http.Request) {
  var employees []models.Employee
  generic_list(&employees, w, req)
}
func employee_get(w http.ResponseWriter, req *http.Request) {
  var employee models.Employee
  generic_get(&employee, w, req)
}
func employee_delete(w http.ResponseWriter, req *http.Request) {
  var employee models.Employee
  generic_delete(&employee, w, req)
}
func employee_create(w http.ResponseWriter, req *http.Request) {
  var employee models.Employee
  generic_create(&employee, w, req)
}
func employee_update(w http.ResponseWriter, req *http.Request) {
  var employee models.Employee
  generic_update(&employee, w, req)
}

func generic_list(obj interface{}, w http.ResponseWriter, req *http.Request) {
  query := db.Find(obj)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  ret, err := json.Marshal(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  w.Write(ret)
}

func generic_get(obj interface{}, w http.ResponseWriter, req *http.Request) {
  id, err := strconv.ParseInt(req.URL.Query().Get(":id"), 10, 64)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  query := db.First(obj, id)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  ret, err := json.Marshal(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  w.Write(ret)
}

func generic_delete(obj interface{}, w http.ResponseWriter, req *http.Request) {
  id, err := strconv.ParseInt(req.URL.Query().Get(":id"), 10, 64)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  reflect.ValueOf(obj).Elem().FieldByName("Id").SetInt(id)
  query := db.Delete(obj)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  w.WriteHeader(204)
}


func generic_create(obj interface{}, w http.ResponseWriter, req *http.Request) {
  decoder := json.NewDecoder(req.Body)
  err := decoder.Decode(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  query := db.Save(obj)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  ret, err := json.Marshal(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  w.Write(ret)
}

func generic_update(obj interface{}, w http.ResponseWriter, req *http.Request) {
  // Get the existing object
  id, err := strconv.ParseInt(req.URL.Query().Get(":id"), 10, 64)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  query := db.First(obj, id)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  // Add fields from request to the object
  decoder := json.NewDecoder(req.Body)
  err = decoder.Decode(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  // Update the object
  query = db.Save(obj)
  if query.Error != nil {
    http.Error(w, query.Error.Error(), 500)
    return
  }
  ret, err := json.Marshal(obj)
  if err != nil {
    http.Error(w, err.Error(), 500)
    return
  }
  w.Write(ret)
}