golang http 中间件

alin-qu 2019-06-26 原文

golang http 中间件

golang的http中间件的实现首先实现一个http的handler接口

type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}

type Router struct {
    route map[string]Handle
}

func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
}

通过函数包裹的方式实现

中间件v1.0

1.通过匿名函数将handler包裹起来然后再调用传进来的handler。在执行传进来的参数之前
就可以做到记录日志等一些中间件的功能

2.如果有多个中间件那么就多个函数一层一层包裹

func withMiddle(h Handle) Handle {
    return func(writer http.ResponseWriter, request *http.Request) {
        t := time.Now()
        defer func() {
            log.Println("time spend is ", time.Since(t))
        }()
        h(writer, request)
    }
}

func (r *Router) Register1(route string, f Handle) {
    r.route[route] = withMiddle(f)
}

func (r *Router) Register2(route string, f Handle) {
    r.route[route] = withMiddLog(withMiddTime(f))
}

Register("/bench", func(writer http.ResponseWriter, request *http.Request) {
    time.Sleep(time.Second)
    fmt.Println("bench sleep 1 second")
})

中间件v1.1

注册的时候可以更加简化一些通过匿名函数的方式当然这种方式没有传递参数
只是作为演示用的

func (r *Router) Register(route string, f HandlerFunc) {
    r.route[route] = withMiddLog(withMiddTime(func(writer http.ResponseWriter, request *http.Request) {
        f()
    }))
}

中间件v2.0

针对中间件v1.1中的没法传递 http中的读写参数的问题可以封装一个context
将http的读写参数都包裹进来这样就可以很方便的处理读写了

func (r *Server) Register(route string, f HandlerFunc) {
    r.route[route] = withMiddLog(withMiddTime(func(writer http.ResponseWriter, request *http.Request) {
        f(r.createContext(writer, request))
    }))
}
r.Register("/bench", func(c *Context) {
        time.Sleep(time.Second)
        fmt.Println("bench sleep 1 second")
        c.Writer.Write([]byte("hello!\r\n"))
    })

golang框架gin中的实现

中间件v3.0

核心理念是将中间件和最后的函数一视同仁。通过一个for循环遍历具体的可以参考代码

func (c *Context) Next() {
    c.index++
    //for中的index++是为了退出循环 否则没法退出
    for ; c.index < len(c.middle); c.index++ {
        c.middle[c.index](c)
    }
}

func withMiddTime() HandleContext {
    return func(c *Context) {
        t := time.Now()
        defer func() {
            fmt.Println("withMiddTime end time", time.Since(t))
        }()
        fmt.Println("withMiddTime start ", time.Since(t))
        c.Next()
    }
}
func (s *Server) Register(path string, f ...HandleContext) {
    handleNew := make([]HandleContext, 0, len(s.handle)+len(f))
    handleNew = append(handleNew, s.handle...)
    handleNew = append(handleNew, f...)
    s.routeHandler(path, func(writer http.ResponseWriter, request *http.Request) {
        s.createContext(writer, request, handleNew).Next()
    })
}