如何在golang中将请求一般化为JSON
我试图将一个类型和一个请求传递到一个函数中,然后在该函数中将请求解组为一个变量并返回它 我认为我的方法是错误的,因为当我尝试这样做时:如何在golang中将请求一般化为JSON,json,http,generics,go,types,Json,Http,Generics,Go,Types,我试图将一个类型和一个请求传递到一个函数中,然后在该函数中将请求解组为一个变量并返回它 我认为我的方法是错误的,因为当我尝试这样做时: package controllers import ( "encoding/json" "errors" "io" "io/ioutil" "reflect" ) func GetTypeFromReq(c *App, ty interface{}) (interface{}, error) { //get
package controllers
import (
"encoding/json"
"errors"
"io"
"io/ioutil"
"reflect"
)
func GetTypeFromReq(c *App, ty interface{}) (interface{}, error) {
//get the type we are going to marshall into
item := reflect.ValueOf(ty)
//define and set the error that we will be returning to null
var retErr error
retErr = nil
//extract the body from the request and defer closing of the body
body, err := ioutil.ReadAll(io.LimitReader(c.Request.Body, 1048576))
defer c.Request.Body.Close()
//handle errors and unmarshal our data
if err != nil {
retErr = errors.New("Failed to Read body: " + err.Error())
} else if err = json.Unmarshal(body, &item); err != nil {
retErr = errors.New("Unmarshal Failed: " + err.Error())
}
return item, retErr
}
我得到错误“接口转换:接口{}是reflect.Value,不是models.User”
有关如何实现此目的的任何提示?修改最后一行的代码:将
用户:=inter.(models.user)
更改为用户:=inter.Interface()(models.user)
,请尝试
接口转换:接口{}是reflect.Value,不是models.User
关于消息错误,我非常直截了当。您的项目
是反映.值
它不是模型.用户
因此,我认为在您的代码中,您可以将项更改为models.User
但是我假设您正在创建一个可以处理所有类型模型的函数,在本例中是models.User{}
您的方法成本很高,因为它使用的是接口
。您可以像这样直接转换传入请求
:
inter, err := GetTypeFromReq(&c, models.User{})
if err != nil {
revel.ERROR.Println(err.Error())
}
user := inter.(models.User)
func GetFromReq(c *App, item interface{}) error {
//extract the body from the request and defer closing of the body
body, err := ioutil.ReadAll(io.LimitReader(c.Request.Body, 1048576))
defer c.Request.Body.Close()
//handle errors and unmarshal our data
if err != nil {
retErr = errors.New("Failed to Read body: " + err.Error())
} else if err = json.Unmarshal(body, item); err != nil {
retErr = errors.New("Unmarshal Failed: " + err.Error())
}
return retErr
}
如果您的主体
与您的模型具有相同的结构,它将为您提供值,如果没有,则为错误
请注意,使用界面时需要小心。你可以从中看到一些指导原则。使用接口:
- 当API的用户需要提供实现细节时
- 当API有多个实现时,它们需要在内部维护
- 当API中可以更改的部分已经确定并且需要解耦时
您的函数将型号的值转换为界面
,然后返回界面
值。这就是它昂贵的原因。以下是如何修改函数以使其按预期工作:
func GetTypeFromReq(c *App, ty models.User) (models.User, error) {
//get the type we are going to marshall into
var item models.User
//define and set the error that we will be returning to nil
var retErr error // this var if the value not define then it is nil. Because error is interface
//extract the body from the request and defer closing of the body
body, err := ioutil.ReadAll(io.LimitReader(c.Request.Body, 1048576))
defer c.Request.Body.Close()
//handle errors and unmarshal our data
if err != nil {
retErr = errors.New("Failed to Read body: " + err.Error())
} else if err = json.Unmarshal(body, &item); err != nil {
retErr = errors.New("Unmarshal Failed: " + err.Error())
}
return item, retErr
}
注意调用以获取reflect.Value
的当前值
以下是一种避免反射和类型断言的方法:
func GetTypeFromReq(c *App, ty interface{}) (interface{}, error) {
// Allocate new value with same type as ty
v := reflect.New(reflect.TypeOf(ty))
//define and set the error that we will be returning to null
var retErr error
retErr = nil
//extract the body from the request and defer closing of the body
body, err := ioutil.ReadAll(io.LimitReader(c.Request.Body, 1048576))
defer c.Request.Body.Close()
//handle errors and unmarshal our data
if err != nil {
retErr = errors.New("Failed to Read body: " + err.Error())
} else if err = json.Unmarshal(body, v.Interface()); err != nil {
retErr = errors.New("Unmarshal Failed: " + err.Error())
}
// v holds a pointer, call Elem() to get the value.
return v.Elem().Interface(), retErr
}
像这样使用它:
inter, err := GetTypeFromReq(&c, models.User{})
if err != nil {
revel.ERROR.Println(err.Error())
}
user := inter.(models.User)
func GetFromReq(c *App, item interface{}) error {
//extract the body from the request and defer closing of the body
body, err := ioutil.ReadAll(io.LimitReader(c.Request.Body, 1048576))
defer c.Request.Body.Close()
//handle errors and unmarshal our data
if err != nil {
retErr = errors.New("Failed to Read body: " + err.Error())
} else if err = json.Unmarshal(body, item); err != nil {
retErr = errors.New("Unmarshal Failed: " + err.Error())
}
return retErr
}
使用a简化代码:
var user models.User
err := GetFromReq(&c, &user)
if err != nil {
revel.ERROR.Println(err.Error())
}
如果c.Request
是*http.Request
且c.Response
是http.ResponseWriter
,则将函数编写为:
func GetFromReq(c *App, item interface{}) error {
defer c.Request.Body.Close()
return json.NewDecoder(io.LimitReader(c.Request.Body, 1048576)).Deocode(item)
}
无需关闭net/http服务器中的请求主体。使用而不是io.LimitReader来防止客户端意外或恶意发送大型请求并浪费服务器资源。完成,woops。我想是的。