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, body := nginxServer.handleRequest(appStatusURL, "GET") fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body) httpCode, body = nginxServer.handleRequest(appStatusURL, "GET") fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body) httpCode, body = nginxServer.handleRequest(appStatusURL, "GET") fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body) httpCode, body = nginxServer.handleRequest(createuserURL, "POST") fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body) httpCode, body = nginxServer.handleRequest(createuserURL, "GET") fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body) } 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 
