英文:
How to write a generic handler in Go?
问题
我需要为一个REST API创建一个HTTP处理程序。
这个REST API有许多不同的对象,这些对象存储在一个数据库中(在我的情况下是MongoDB)。
目前,我需要为每个对象的每个操作编写一个处理程序。
我想找到一种像使用泛型一样的方法,可以编写一个通用的处理程序,可以处理特定的操作,但适用于任何类型的对象(因为在大多数情况下,它基本上只是CRUD操作)。
我该如何做到这一点?
以下是我想要转换为通用处理程序的示例:
func IngredientIndex(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
ingredients := []data.Ingredient{}
err := db.C("ingredients").Find(bson.M{}).All(&ingredients)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(ingredients)
}
func IngredientGet(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
vars := mux.Vars(r)
logger := r.Context().Value("Logger").(zap.Logger)
db := r.Context().Value("Database").(*mgo.Database)
ingredient := data.Ingredient{}
err := db.C("ingredients").Find(bson.M{"_id": bson.ObjectIdHex(vars["id"])}).One(&ingredient)
if err != nil {
w.WriteHeader(404)
logger.Info("Fail to find entity", zap.Error(err))
} else {
json.NewEncoder(w).Encode(ingredient)
}
}
基本上,我需要一个像这样的处理程序(这是我尝试但不起作用的示例):
func ObjectIndex(collection string, container interface{}) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
objects := container
err := db.C(collection).Find(bson.M{}).All(&objects)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(objects)
}
}
我该如何做到这一点?
英文:
I need to create a HTTP Handler for a REST API.
This REST API have many different objects that are stored in a database (MongoDB in my case).
Currently, I need to write one handler per action per object.
I would like to find a way like it's possible with Generics to write a generic handler that could handle a specific action but for any kind of object (As basically it's just CRUD in most of the case)
How can I do this ?
Here is examples of Handlers I would like to transform into a generic one :
func IngredientIndex(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
ingredients := []data.Ingredient{}
err := db.C("ingredients").Find(bson.M{}).All(&ingredients)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(ingredients)
}
func IngredientGet(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
vars := mux.Vars(r)
logger := r.Context().Value("Logger").(zap.Logger)
db := r.Context().Value("Database").(*mgo.Database)
ingredient := data.Ingredient{}
err := db.C("ingredients").Find(bson.M{"_id": bson.ObjectIdHex(vars["id"])}).One(&ingredient)
if err != nil {
w.WriteHeader(404)
logger.Info("Fail to find entity", zap.Error(err))
} else {
json.NewEncoder(w).Encode(ingredient)
}
}
Basically I would need a handler like this (This is my tentative that doesn't work) :
func ObjectIndex(collection string, container interface{}) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
objects := container
err := db.C(collection).Find(bson.M{}).All(&objects)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(objects)
}
How can I do that ?
答案1
得分: 3
使用reflect包在每次调用时创建一个新的容器:
func ObjectIndex(collection string, container interface{}) func(http.ResponseWriter, *http.Request) {
t := reflect.TypeOf(container)
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
objects := reflect.New(t).Interface()
err := db.C(collection).Find(bson.M{}).All(objects)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(objects)
}
}
像这样调用它:
h := ObjectIndex("ingredients", data.Ingredient{})
假设data.Ingredient
是一个切片类型。
英文:
Use the reflect package to create a new container on each invocation:
func ObjectIndex(collection string, container interface{}) func(http.ResponseWriter, *http.Request) {
t := reflect.TypeOf(container)
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json; charset=UTF-8")
db := r.Context().Value("Database").(*mgo.Database)
objects := reflect.New(t).Interface()
err := db.C(collection).Find(bson.M{}).All(objects)
if err != nil {
panic(err)
}
json.NewEncoder(w).Encode(objects)
}
Call it like this:
h := ObjectIndex("ingredients", data.Ingredient{})
assuming that data.Indgredient
is a slice type.
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