golang 中间件的实现本质:
写一个func,接受handler并且返回handler
把私货写在func里面,从而实现把你要写的操作执行了之后,再把原有的流程进行下去
一个好的中间件有一个责任就是可插拔并且自足。
例子:
package mainimport ( "fmt" "github.com/devfeel/dotweb")func main() { app := dotweb.New() // App注册中间件 app.Use(NewSessionAuth()) // 开启SESSION app.HttpServer.SetEnabledSession(true) // 设置路由 输出字符串 Hello Dotweb app.HttpServer.GET("/", func(ctx dotweb.Context) error { method := ctx.Request().Method return ctx.WriteString("Hello Dotweb\n" + "Method:" + method) }) //开启服务 端口号 fmt.Println("dotweb.StartServer => 8080") err := app.StartServer(8080) fmt.Println("dotweb.StartServer error => ", err)}// SessionAuth 结构体type SessionAuth struct { dotweb.BaseMiddlware}// Handle 处理程序func (m *SessionAuth) Handle(ctx dotweb.Context) error { fmt.Println("SessionID = ", ctx.SessionID(), " RequestURI = ", ctx.Request().RequestURI) return m.Next(ctx)}// NewSessionAuth Newfunc NewSessionAuth() *SessionAuth { sAuth := new(SessionAuth) return sAu}
Handle是什么时候被调用的?
我们看看BaseMiddlWare的源码:
// BaseMiddleware is the base struct, user defined middleware should extend thistype BaseMiddleware struct {next MiddlewareexcludeRouters map[string]struct{}}func (bm *BaseMiddleware) SetNext(m Middleware) {bm.next = m}func (bm *BaseMiddleware) Next(ctx Context) error {httpCtx := ctx.(*HttpContext)if httpCtx.middlewareStep == "" {httpCtx.middlewareStep = middleware_App}if bm.next == nil {if httpCtx.middlewareStep == middleware_App {httpCtx.middlewareStep = middleware_Groupif len(httpCtx.RouterNode().GroupMiddlewares()) > 0 {return httpCtx.RouterNode().GroupMiddlewares()[0].Handle(ctx)}}if httpCtx.middlewareStep == middleware_Group {httpCtx.middlewareStep = middleware_Routerif len(httpCtx.RouterNode().Middlewares()) > 0 {return httpCtx.RouterNode().Middlewares()[0].Handle(ctx)}}if httpCtx.middlewareStep == middleware_Router {return httpCtx.Handler()(ctx)}} else {// check exclude configif ctx.RouterNode().Node().hasExcludeMiddleware && bm.next.HasExclude() {if bm.next.ExistsExcludeRouter(ctx.RouterNode().Node().fullPath) {return bm.next.Next(ctx)}}return bm.next.Handle(ctx)}return n}
通过这个代码我们大概能看出:
BaseMiddleware其实是一个链表的node
中间件组成了一个链表,并且有不同的类型
有group中间件和普通中间件
根据当前ctx所处的处理步骤决定调用哪一个中间件
最后调用ctx的handler
自定义的middleware要继承 BaseMiddleware
并且实现handle
func (asm *ApiSignMiddleware) Handle(ctx dotweb.Context) error {if sign := ctx.Request().QueryHeader("Sign"); len(sign) <= 0 {return ctx.WriteJsonC(http.StatusBadRequest, models.Response{Err: common.ErrSignParams, Data: nil})} else {uri := ctx.Request().RequestURIif index := strings.Index(uri, "?"); index != -1 {uri = uri[:index]}if ok := checkSign(sign, uri); !ok {return ctx.WriteJsonC(http.StatusBadRequest, models.Response{Err: common.ErrSignParams, Data: nil})}return asm.Next(ctx)}}
这样就可以对传进来的Contex进行解析
分析一下blogserver里面用到的middleware:
CrosMiddleware
func (cm *CrosMiddleware) Handle(ctx dotweb.Context) error {if strings.Contains(ctx.Request().RequestURI, "v1") && ctx.Request().Method != "OPTIONS" {if sign := ctx.Request().QueryHeader("Sign"); len(sign) <= 0 {return ctx.WriteJsonC(http.StatusBadRequest, models.Response{Err: common.ErrSignParams, Data: nil})} else {uri := ctx.Request().RequestURIif index := strings.Index(uri, "?"); index != -1 {uri = uri[:index]}if ok := checkSign(sign, uri); !ok {return ctx.WriteJsonC(http.StatusBadRequest, models.Response{Err: common.ErrSignParams, Data: nil})}return cm.Next(ctx)}}return cm.Next(ctx)}
CrosMiddleware 对uri的非参数部分调用checkSign
//验证签名 (requestUri(不含query)+secret)func checkSign(sign, uri string) bool {result := utils.Md5(uri + config.Config().SecretKey)return result == sign}
传过来得header里面得sign值应该跟 uri + 配置文件里面的 SecretKey 取md5 一致