Go 代理模式讲解和代码示例 #
代理是一种结构型设计模式， 让你能提供真实服务对象的替代品给客户端使用。 代理接收客户端的请求并进行一些处理 （访问控制和缓存等）， 然后再将请求传递给服务对象。
代理对象拥有和服务对象相同的接口， 这使得当其被传递给客户端时可与真实对象互换。
概念示例 #
Nginx 这样的 Web 服务器可充当应用程序服务器的代理：
- 提供了对应用程序服务器的受控访问权限。
- 可限制速度。
- 可缓存请求。
server.go: 主体 #
package main
type server interface {
handleRequest(string, string) (int, string)
}
nginx.go: 代理 #
package main
type Nginx struct {
application *Application
maxAllowedRequest int
rateLimiter map[string]int
}
func newNginxServer() *Nginx {
return &Nginx{
application: &Application{},
maxAllowedRequest: 2,
rateLimiter: make(map[string]int),
}
}
func (n *Nginx) handleRequest(url, method string) (int, string) {
allowed := n.checkRateLimiting(url)
if !allowed {
return 403, "Not Allowed"
}
return n.application.handleRequest(url, method)
}
func (n *Nginx) checkRateLimiting(url string) bool {
if n.rateLimiter[url] == 0 {
n.rateLimiter[url] = 1
}
if n.rateLimiter[url] > n.maxAllowedRequest {
return false
}
n.rateLimiter[url] = n.rateLimiter[url] + 1
return true
}
application.go: 真实主体 #
package main
type Application struct{}
func (a *Application) handleRequest(url, method string) (int, string) {
if url == "/app/status" && method == "GET" {
return 200, "ok"
}
if url == "/create/user" && method == "POST" {
return 201, "user created"
}
return 404, "Not OK"
}
main.go: 客户端代码 #
package main
import "fmt"
func main() {
nginxServer := newNginxServer()
appStatusURL := "/app/status"
createuserURL := "/create/user"
httpCode, msg := nginxServer.handleRequest(appStatusURL, "GET")
fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, msg)
httpCode, msg = nginxServer.handleRequest(appStatusURL, "GET")
fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, msg)
httpCode, msg = nginxServer.handleRequest(appStatusURL, "GET")
fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, msg)
httpCode, msg = nginxServer.handleRequest(createuserURL, "POST")
fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, msg)
httpCode, msg = nginxServer.handleRequest(createuserURL, "GET")
fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, msg)
}
output.txt: 执行结果 #
Url: /app/status
HttpCode: 200
Body: ok
Url: /app/status
HttpCode: 200
Body: ok
Url: /app/status
HttpCode: 403
Body: Not Allowed
Url: /app/status
HttpCode: 201
Body: user created
Url: /app/status
HttpCode: 404
Body: Not OK