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277 lines
8.8 KiB
277 lines
8.8 KiB
4 years ago
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# 13.2 自定义路由器设计
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## HTTP路由
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HTTP路由组件负责将HTTP请求交到对应的函数处理(或者是一个struct的方法),如前面小节所描述的结构图,路由在框架中相当于一个事件处理器,而这个事件包括:
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- 用户请求的路径(path)(例如:/user/123,/article/123),当然还有查询串信息(例如?id=11)
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- HTTP的请求方法(method)(GET、POST、PUT、DELETE、PATCH等)
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路由器就是根据用户请求的事件信息转发到相应的处理函数(控制层)。
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## 默认的路由实现
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在3.4小节有过介绍Go的http包的详解,里面介绍了Go的http包如何设计和实现路由,这里继续以一个例子来说明:
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```Go
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func fooHandler(w http.ResponseWriter, r *http.Request) {
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fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
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}
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http.HandleFunc("/foo", fooHandler)
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http.HandleFunc("/bar", func(w http.ResponseWriter, r *http.Request) {
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fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
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})
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log.Fatal(http.ListenAndServe(":8080", nil))
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```
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上面的例子调用了http默认的DefaultServeMux来添加路由,需要提供两个参数,第一个参数是希望用户访问此资源的URL路径(保存在r.URL.Path),第二参数是即将要执行的函数,以提供用户访问的资源。路由的思路主要集中在两点:
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- 添加路由信息
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- 根据用户请求转发到要执行的函数
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Go默认的路由添加是通过函数`http.Handle`和`http.HandleFunc`等来添加,底层都是调用了`DefaultServeMux.Handle(pattern string, handler Handler)`,这个函数会把路由信息存储在一个map信息中`map[string]muxEntry`,这就解决了上面说的第一点。
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Go监听端口,然后接收到tcp连接会扔给Handler来处理,上面的例子默认nil即为`http.DefaultServeMux`,通过`DefaultServeMux.ServeHTTP`函数来进行调度,遍历之前存储的map路由信息,和用户访问的URL进行匹配,以查询对应注册的处理函数,这样就实现了上面所说的第二点。
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```Go
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for k, v := range mux.m {
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if !pathMatch(k, path) {
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continue
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}
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if h == nil || len(k) > n {
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n = len(k)
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h = v.h
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}
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}
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```
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## beego框架路由实现
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目前几乎所有的Web应用路由实现都是基于http默认的路由器,但是Go自带的路由器有几个限制:
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- 不支持参数设定,例如/user/:uid 这种泛类型匹配
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- 无法很好的支持REST模式,无法限制访问的方法,例如上面的例子中,用户访问/foo,可以用GET、POST、DELETE、HEAD等方式访问
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- 一般网站的路由规则太多了,编写繁琐。我前面自己开发了一个API应用,路由规则有三十几条,这种路由多了之后其实可以进一步简化,通过struct的方法进行一种简化
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beego框架的路由器基于上面的几点限制考虑设计了一种REST方式的路由实现,路由设计也是基于上面Go默认设计的两点来考虑:存储路由和转发路由
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### 存储路由
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针对前面所说的限制点,我们首先要解决参数支持就需要用到正则,第二和第三点我们通过一种变通的方法来解决,REST的方法对应到struct的方法中去,然后路由到struct而不是函数,这样在转发路由的时候就可以根据method来执行不同的方法。
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根据上面的思路,我们设计了两个数据类型controllerInfo(保存路径和对应的struct,这里是一个reflect.Type类型)和ControllerRegistor(routers是一个slice用来保存用户添加的路由信息,以及beego框架的应用信息)
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```Go
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type controllerInfo struct {
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regex *regexp.Regexp
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params map[int]string
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controllerType reflect.Type
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}
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type ControllerRegistor struct {
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routers []*controllerInfo
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Application *App
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}
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```
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ControllerRegistor对外的接口函数有
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```Go
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func (p *ControllerRegistor) Add(pattern string, c ControllerInterface)
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```
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详细的实现如下所示:
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```Go
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func (p *ControllerRegistor) Add(pattern string, c ControllerInterface) {
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parts := strings.Split(pattern, "/")
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j := 0
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params := make(map[int]string)
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for i, part := range parts {
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if strings.HasPrefix(part, ":") {
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expr := "([^/]+)"
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//a user may choose to override the defult expression
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// similar to expressjs: ‘/user/:id([0-9]+)’
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if index := strings.Index(part, "("); index != -1 {
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expr = part[index:]
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part = part[:index]
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}
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params[j] = part
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parts[i] = expr
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j++
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}
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}
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//recreate the url pattern, with parameters replaced
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//by regular expressions. then compile the regex
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pattern = strings.Join(parts, "/")
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regex, regexErr := regexp.Compile(pattern)
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if regexErr != nil {
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//TODO add error handling here to avoid panic
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panic(regexErr)
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return
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}
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//now create the Route
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t := reflect.Indirect(reflect.ValueOf(c)).Type()
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route := &controllerInfo{}
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route.regex = regex
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route.params = params
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route.controllerType = t
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p.routers = append(p.routers, route)
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}
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```
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### 静态路由实现
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上面我们实现的动态路由的实现,Go的http包默认支持静态文件处理FileServer,由于我们实现了自定义的路由器,那么静态文件也需要自己设定,beego的静态文件夹路径保存在全局变量StaticDir中,StaticDir是一个map类型,实现如下:
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```Go
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func (app *App) SetStaticPath(url string, path string) *App {
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StaticDir[url] = path
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return app
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}
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```
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应用中设置静态路径可以使用如下方式实现:
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```Go
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beego.SetStaticPath("/img","/static/img")
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```
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### 转发路由
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转发路由是基于ControllerRegistor里的路由信息来进行转发的,详细的实现如下代码所示:
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```Go
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// AutoRoute
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func (p *ControllerRegistor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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defer func() {
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if err := recover(); err != nil {
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if !RecoverPanic {
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// go back to panic
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panic(err)
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} else {
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Critical("Handler crashed with error", err)
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for i := 1; ; i += 1 {
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_, file, line, ok := runtime.Caller(i)
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if !ok {
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break
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}
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Critical(file, line)
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}
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}
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}
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}()
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var started bool
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for prefix, staticDir := range StaticDir {
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if strings.HasPrefix(r.URL.Path, prefix) {
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file := staticDir + r.URL.Path[len(prefix):]
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http.ServeFile(w, r, file)
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started = true
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return
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}
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}
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requestPath := r.URL.Path
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//find a matching Route
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for _, route := range p.routers {
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//check if Route pattern matches url
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if !route.regex.MatchString(requestPath) {
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continue
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}
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//get submatches (params)
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matches := route.regex.FindStringSubmatch(requestPath)
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//double check that the Route matches the URL pattern.
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if len(matches[0]) != len(requestPath) {
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continue
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}
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params := make(map[string]string)
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if len(route.params) > 0 {
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//add url parameters to the query param map
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values := r.URL.Query()
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for i, match := range matches[1:] {
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values.Add(route.params[i], match)
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params[route.params[i]] = match
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}
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//reassemble query params and add to RawQuery
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r.URL.RawQuery = url.Values(values).Encode() + "&" + r.URL.RawQuery
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//r.URL.RawQuery = url.Values(values).Encode()
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}
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//Invoke the request handler
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vc := reflect.New(route.controllerType)
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init := vc.MethodByName("Init")
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in := make([]reflect.Value, 2)
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ct := &Context{ResponseWriter: w, Request: r, Params: params}
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in[0] = reflect.ValueOf(ct)
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in[1] = reflect.ValueOf(route.controllerType.Name())
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init.Call(in)
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in = make([]reflect.Value, 0)
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method := vc.MethodByName("Prepare")
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method.Call(in)
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if r.Method == "GET" {
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method = vc.MethodByName("Get")
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method.Call(in)
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} else if r.Method == "POST" {
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method = vc.MethodByName("Post")
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method.Call(in)
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} else if r.Method == "HEAD" {
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method = vc.MethodByName("Head")
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method.Call(in)
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} else if r.Method == "DELETE" {
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method = vc.MethodByName("Delete")
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method.Call(in)
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} else if r.Method == "PUT" {
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method = vc.MethodByName("Put")
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method.Call(in)
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} else if r.Method == "PATCH" {
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method = vc.MethodByName("Patch")
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method.Call(in)
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} else if r.Method == "OPTIONS" {
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method = vc.MethodByName("Options")
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method.Call(in)
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}
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if AutoRender {
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method = vc.MethodByName("Render")
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method.Call(in)
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}
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method = vc.MethodByName("Finish")
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method.Call(in)
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started = true
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break
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}
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//if no matches to url, throw a not found exception
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if started == false {
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http.NotFound(w, r)
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}
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}
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```
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### 使用入门
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基于这样的路由设计之后就可以解决前面所说的三个限制点,使用的方式如下所示:
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基本的使用注册路由:
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```Go
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beego.BeeApp.RegisterController("/", &controllers.MainController{})
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```
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参数注册:
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```Go
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beego.BeeApp.RegisterController("/:param", &controllers.UserController{})
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```
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正则匹配:
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```Go
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beego.BeeApp.RegisterController("/users/:uid([0-9]+)", &controllers.UserController{})
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```
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## links
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* [目录](<preface.md>)
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* 上一章: [项目规划](<13.1.md>)
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* 下一节: [controller设计](<13.3.md>)
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