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nethttp和gin 路由

2023-06-28 21:17:56来源：博客园

net/http 路由注册

func test1() {    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {        fmt.Fprintf(w, "Hello world!")    })    err := http.ListenAndServe(":9001", nil)    if err != nil {        log.Fatal("ListenAndServer:", err)    }}

在使用ListenAndServe这个方法时，系统就会给我们指派一个路由器，DefaultServeMux是系统默认使用的路由器，如果ListenAndServe这个方法的第2个参数传入nil，系统就会默认使用DefaultServeMux。当然，这里也可以传入自定义的路由器。

先看http.HandleFunc("/", ...)，从HandleFunc方法点进去，如下：

func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {    DefaultServeMux.HandleFunc(pattern, handler)}

在这里调用了DefaultServeMux的HandleFunc方法，这个方法有两个参数，pattern是匹配的路由规则，handler表示这个路由规则对应的处理方法，并且这个处理方法有两个参数。

(资料图)

在我们书写的代码示例中，pattern对应/，handler对应sayHello，当我们在浏览器中输入http://localhost:9001时，就会触发匿名函数。

我们再顺着DefaultServeMux的HandleFunc方法继续点下去，如下：

func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {    if handler == nil {        panic("http: nil handler")    }    mux.Handle(pattern, HandlerFunc(handler))}

在这个方法中，路由器又调用了Handle方法，注意这个Handle方法的第2个参数，将之前传入的handler这个响应方法强制转换成了HandlerFunc类型。

这个HandlerFunc类型到底是个什么呢？如下：

type HandlerFunc func(ResponseWriter, *Request)

看来和我们定义的"/"的匿名函数的类型都差不多。但是！！！这个HandlerFunc默认实现了ServeHTTP接口！这样HandlerFunc对象就有了ServeHTTP方法！如下：

// ServeHTTP calls f(w, r).func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {    f(w, r)}

接下来，我们返回去继续看mux的Handle方法，也就是这段代码mux.Handle(pattern, HandlerFunc(handler))。这段代码做了哪些事呢？源码如下

// Handle registers the handler for the given pattern.// If a handler already exists for pattern, Handle panics.func (mux *ServeMux) Handle(pattern string, handler Handler) {    mux.mu.Lock()    defer mux.mu.Unlock()    if pattern == "" {        panic("http: invalid pattern")    }    if handler == nil {        panic("http: nil handler")    }    if _, exist := mux.m[pattern]; exist {        panic("http: multiple registrations for " + pattern)    }    if mux.m == nil {        mux.m = make(map[string]muxEntry)    }    e := muxEntry{h: handler, pattern: pattern}    mux.m[pattern] = e    if pattern[len(pattern)-1] == "/" {        mux.es = appendSorted(mux.es, e)    }    if pattern[0] != "/" {        mux.hosts = true    }}

主要就做了一件事，向DefaultServeMux的map[string]muxEntry中增加对应的路由规则和handler。

map[string]muxEntry是个什么鬼？

map是一个字典对象，它保存的是key-value。
[string]表示这个字典的key是string类型的，这个key值会保存我们的路由规则。
muxEntry是一个实例对象，这个对象内保存了路由规则对应的处理方法。
mux.es为模糊匹配有长倒短排序比如有路由/hello/访问/hello/world时没有路由会落到/hello/上

找到相应代码，如下：

// 路由器type ServeMux struct {    mu    sync.RWMutex    m     map[string]muxEntry    es    []muxEntry // slice of entries sorted from longest to shortest.    hosts bool       // whether any patterns contain hostnames}type muxEntry struct {    h       Handler    pattern string}// 路由响应方法type Handler interface {    ServeHTTP(ResponseWriter, *Request)}

net/http 运行

第二部分主要就是研究这句代码err := http.ListenAndServe(":9001",nil)，也就是ListenAndServe这个方法。从这个方法点进去，如下：

func ListenAndServe(addr string, handler Handler) error {    server := &Server{Addr: addr, Handler: handler}    return server.ListenAndServe()}

在这个方法中，初始化了一个server对象，然后调用这个server对象的ListenAndServe方法，在这个方法中，如下：

func (srv *Server) ListenAndServe() error {    if srv.shuttingDown() {        return ErrServerClosed    }    addr := srv.Addr    if addr == "" {        addr = ":http"    }    ln, err := net.Listen("tcp", addr)    if err != nil {        return err    }    return srv.Serve(ln)}

在这个方法中，调用了net.Listen("tcp", addr)，也就是底层用TCP协议搭建了一个服务，然后监控我们设置的端口。

代码的最后，调用了srv的Serve方法，如下：

func (srv *Server) Serve(l net.Listener) error {    if fn := testHookServerServe; fn != nil {        fn(srv, l) // call hook with unwrapped listener    }    origListener := l    l = &onceCloseListener{Listener: l}    defer l.Close()    if err := srv.setupHTTP2_Serve(); err != nil {        return err    }    if !srv.trackListener(&l, true) {        return ErrServerClosed    }    defer srv.trackListener(&l, false)    baseCtx := context.Background()    if srv.BaseContext != nil {        baseCtx = srv.BaseContext(origListener)        if baseCtx == nil {            panic("BaseContext returned a nil context")        }    }    var tempDelay time.Duration // how long to sleep on accept failure    ctx := context.WithValue(baseCtx, ServerContextKey, srv)    for {        rw, err := l.Accept()        if err != nil {            select {            case <-srv.getDoneChan():                return ErrServerClosed            default:            }            if ne, ok := err.(net.Error); ok && ne.Temporary() {                if tempDelay == 0 {                    tempDelay = 5 * time.Millisecond                } else {                    tempDelay *= 2                }                if max := 1 * time.Second; tempDelay > max {                    tempDelay = max                }                srv.logf("http: Accept error: %v; retrying in %v", err, tempDelay)                time.Sleep(tempDelay)                continue            }            return err        }        connCtx := ctx        if cc := srv.ConnContext; cc != nil {            connCtx = cc(connCtx, rw)            if connCtx == nil {                panic("ConnContext returned nil")            }        }        tempDelay = 0        c := srv.newConn(rw)        c.setState(c.rwc, StateNew, runHooks) // before Serve can return        go c.serve(connCtx)    }}

最后3段代码比较重要，也是Go语言支持高并发的体现，如下：

c := srv.newConn(rw)c.setState(c.rwc, StateNew, runHooks) // before Serve can returngo c.serve(connCtx)

上面那一大坨代码，总体意思是进入方法后，首先开了一个for循环，在for循环内时刻Accept请求，请求来了之后，会为每个请求创建一个Conn，然后单独开启一个goroutine，把这个请求的数据当做参数扔给这个Conn去服务：go c.serve()。用户的每一次请求都是在一个新的goroutine去服务，每个请求间相互不影响。

在conn的serve方法中，有一句代码很重要，如下：

serverHandler{c.server}.ServeHTTP(w, w.req)

表示serverHandler也实现了ServeHTTP接口，ServeHTTP方法实现如下：

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {    handler := sh.srv.Handler    if handler == nil {        handler = DefaultServeMux    }    if req.RequestURI == "*" && req.Method == "OPTIONS" {        handler = globalOptionsHandler{}    }    if req.URL != nil && strings.Contains(req.URL.RawQuery, ";") {        var allowQuerySemicolonsInUse int32        req = req.WithContext(context.WithValue(req.Context(), silenceSemWarnContextKey, func() {            atomic.StoreInt32(&allowQuerySemicolonsInUse, 1)        }))        defer func() {            if atomic.LoadInt32(&allowQuerySemicolonsInUse) == 0 {                sh.srv.logf("http: URL query contains semicolon, which is no longer a supported separator; parts of the query may be stripped when parsed; see golang.org/issue/25192")            }        }()    }    handler.ServeHTTP(rw, req)}

在这里如果handler为空（这个handler就可以理解为是我们自定义的路由器），就会使用系统默认的DefaultServeMux，代码的最后调用了DefaultServeMux的ServeHTTP()

func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {    if r.RequestURI == "*" {        if r.ProtoAtLeast(1, 1) {            w.Header().Set("Connection", "close")        }        w.WriteHeader(StatusBadRequest)        return    }    h, _ := mux.Handler(r)  //这里返回的h是Handler接口对象    h.ServeHTTP(w, r)  //调用Handler接口对象的ServeHTTP方法实际上就调用了我们定义的sayHello方法}

func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string) {    // CONNECT requests are not canonicalized.    if r.Method == "CONNECT" {        // If r.URL.Path is /tree and its handler is not registered,        // the /tree -> /tree/ redirect applies to CONNECT requests        // but the path canonicalization does not.        if u, ok := mux.redirectToPathSlash(r.URL.Host, r.URL.Path, r.URL); ok {            return RedirectHandler(u.String(), StatusMovedPermanently), u.Path        }        return mux.handler(r.Host, r.URL.Path)    }    // All other requests have any port stripped and path cleaned    // before passing to mux.handler.    host := stripHostPort(r.Host)    path := cleanPath(r.URL.Path)    // If the given path is /tree and its handler is not registered,    // redirect for /tree/.    if u, ok := mux.redirectToPathSlash(host, path, r.URL); ok {        return RedirectHandler(u.String(), StatusMovedPermanently), u.Path    }    if path != r.URL.Path {        _, pattern = mux.handler(host, path)        u := &url.URL{Path: path, RawQuery: r.URL.RawQuery}        return RedirectHandler(u.String(), StatusMovedPermanently), pattern    }    return mux.handler(host, r.URL.Path)}func (mux *ServeMux) handler(host, path string) (h Handler, pattern string) {    mux.mu.RLock()    defer mux.mu.RUnlock()    // Host-specific pattern takes precedence over generic ones    if mux.hosts {        h, pattern = mux.match(host + path)    }    if h == nil {        h, pattern = mux.match(path)    }    if h == nil {        h, pattern = NotFoundHandler(), ""    }    return}func (mux *ServeMux) match(path string) (h Handler, pattern string) {    // Check for exact match first.    v, ok := mux.m[path]    if ok {        return v.h, v.pattern    }    // Check for longest valid match.  mux.es contains all patterns    // that end in / sorted from longest to shortest.    for _, e := range mux.es {        if strings.HasPrefix(path, e.pattern) {            return e.h, e.pattern        }    }    return nil, ""}

它会根据用户请求的URL到路由器里面存储的map中匹配，匹配成功就会返回存储的handler，调用这个handler的ServeHTTP()就可以执行到相应的处理方法了，这个处理方法实际上就是我们刚开始定义的sayHello()，只不过这个sayHello()被HandlerFunc又包了一层，因为HandlerFunc实现了ServeHTTP接口，所以在调用HandlerFunc对象的ServeHTTP()时，实际上在ServeHTTP ()的内部调用了我们的sayHello()。

总结

调用http.ListenAndServe(":9090",nil)
实例化server
调用server的ListenAndServe()
调用server的Serve方法，开启for循环，在循环中Accept请求
对每一个请求实例化一个Conn，并且开启一个goroutine为这个请求进行服务go c.serve()
读取每个请求的内容c.readRequest()
调用serverHandler的ServeHTTP()，如果handler为空，就把handler设置为系统默认的路由器DefaultServeMux
调用handler的ServeHTTP()=>实际上是调用了DefaultServeMux的ServeHTTP()
在ServeHTTP()中会调用路由对应处理handler
在路由对应处理handler中会执行sayHello()

有一个需要注意的点： DefaultServeMux和路由对应的处理方法handler都实现了ServeHTTP接口，他们俩都有ServeHTTP方法，但是方法要达到的目的不同，在DefaultServeMux的ServeHttp()里会执行路由对应的处理handler的ServeHttp()。

自定义个简单的路由

package muximport (    "net/http"    "strings")type muxEntry struct {    h TesthandleFunc}type TesthandleFunc func(http.ResponseWriter, *http.Request)type TestHandler struct {    routes map[string]map[string]muxEntry}func (h *TestHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {    method := strings.ToUpper(r.Method)    path := r.URL.Path    if route, ok := h.routes[method]; ok {        if entry, ok := route[path]; ok {            entry.h(w, r)            return        }    }    w.WriteHeader(http.StatusNotFound)}func Newhandler() *TestHandler {    return &TestHandler{routes: make(map[string]map[string]muxEntry)}}func (h *TestHandler) Handle(method, path string, handler TesthandleFunc) {    method = strings.ToUpper(method)    if _, ok := h.routes[method]; !ok {        h.routes[method] = make(map[string]muxEntry)    }    h.routes[method][path] = muxEntry{handler}}

package mainimport (    "fmt"    "net/http"    "study/mux")func main() {    handler := mux.Newhandler()    handler.Handle("GET", "/hello", func(rw http.ResponseWriter, r *http.Request) {        rw.Write([]byte("Hello World"))    })    handler.Handle("Post", "/hello/world", func(rw http.ResponseWriter, r *http.Request) {        fmt.Fprintln(rw, "你好")    })    http.ListenAndServe(":9002", handler)}

自定义context

package routerimport (    "encoding/json"    "net/http"    "strings")type Context struct {    w http.ResponseWriter    r *http.Request}func (c *Context) Json(code int, v interface{}) {    c.w.Header().Set("Content-Type", "application/json")    c.w.WriteHeader(code)    s, _ := json.Marshal(v)    c.w.Write(s)}type Routerfunc func(c *Context)type RouterHandler struct {    routes map[string]map[string]Routerfunc}func NewRouterHandler() *RouterHandler {    return &RouterHandler{routes: make(map[string]map[string]Routerfunc)}}func (h *RouterHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {    method := strings.ToUpper(r.Method)    path := r.URL.Path    c := &Context{w: w, r: r}    if route, ok := h.routes[method]; ok {        if h, ok := route[path]; ok {            h(c)            return        }    }    w.WriteHeader(http.StatusNotFound)}func (h *RouterHandler) Handle(method, path string, handler Routerfunc) {    method = strings.ToUpper(method)    if _, ok := h.routes[method]; !ok {        h.routes[method] = make(map[string]Routerfunc)    }    h.routes[method][path] = handler}func (r *RouterHandler) Run(addr string) error {    return http.ListenAndServe(addr, r)}

Gin

type Engine struct {    RouterGroup    pool     sync.Pool    trees    methodTrees}// trietype RouterGroup struct {    basePath string    engine   *Engine}func (engine *Engine) ServeHTTP(w http.ResponseWriter, req *http.Request) {    c := engine.pool.Get().(*Context) // 从pool 拿出一个context    c.writermem.reset(w) // 记录http.ResponseWriter 及 *http.Request    c.Request = req    c.reset() // 重置上一个留下的值    engine.handleHTTPRequest(c)    engine.pool.Put(c) // 把用完的context放回池子}// get: /bac

添加路由

func (group *RouterGroup) handle(httpMethod, relativePath string, handlers HandlersChain) IRoutes {    absolutePath := group.calculateAbsolutePath(relativePath)    handlers = group.combineHandlers(handlers)    group.engine.addRoute(httpMethod, absolutePath, handlers)    return group.returnObj()}

Context

type Context struct {    Request   *http.Request    Writer    ResponseWriter    Params   Params    handlers HandlersChain    index    int8    fullPath string    engine       *Engine    params       *Params    skippedNodes *[]skippedNode    // This mutex protect Keys map    mu sync.RWMutex    // Keys is a key/value pair exclusively for the context of each request.    Keys map[string]interface{}    // Errors is a list of errors attached to all the handlers/middlewares who used this context.    Errors errorMsgs    // Accepted defines a list of manually accepted formats for content negotiation.    Accepted []string    // queryCache use url.ParseQuery cached the param query result from c.Request.URL.Query()    queryCache url.Values    // formCache use url.ParseQuery cached PostForm contains the parsed form data from POST, PATCH,    // or PUT body parameters.    formCache url.Values    // SameSite allows a server to define a cookie attribute making it impossible for    // the browser to send this cookie along with cross-site requests.    sameSite http.SameSite}func (c *Context) Next() {    c.index++    for c.index < int8(len(c.handlers)) {        c.handlers[c.index](c)        c.index++    }}

func (engine *Engine) handleHTTPRequest(c *Context) {    httpMethod := c.Request.Method    rPath := c.Request.URL.Path    unescape := false    if engine.UseRawPath && len(c.Request.URL.RawPath) > 0 {        rPath = c.Request.URL.RawPath        unescape = engine.UnescapePathValues    }    if engine.RemoveExtraSlash {        rPath = cleanPath(rPath)    }    // Find root of the tree for the given HTTP method    t := engine.trees    for i, tl := 0, len(t); i < tl; i++ {        if t[i].method != httpMethod {            continue        }        root := t[i].root        // Find route in tree        value := root.getValue(rPath, c.params, c.skippedNodes, unescape)        if value.params != nil {            c.Params = *value.params        }        if value.handlers != nil {            c.handlers = value.handlers            c.fullPath = value.fullPath            c.Next()            c.writermem.WriteHeaderNow()            return        }        if httpMethod != http.MethodConnect && rPath != "/" {            if value.tsr && engine.RedirectTrailingSlash {                redirectTrailingSlash(c)                return            }            if engine.RedirectFixedPath && redirectFixedPath(c, root, engine.RedirectFixedPath) {                return            }        }        break    }    if engine.HandleMethodNotAllowed {        for _, tree := range engine.trees {            if tree.method == httpMethod {                continue            }            if value := tree.root.getValue(rPath, nil, c.skippedNodes, unescape); value.handlers != nil {                c.handlers = engine.allNoMethod                serveError(c, http.StatusMethodNotAllowed, default405Body)                return            }        }    }    c.handlers = engine.allNoRoute    serveError(c, http.StatusNotFound, default404Body)}

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