golang gin大行其道!

下面是gin用來構(gòu)建路由用到的結(jié)構(gòu)代碼
type Engine struct {    RouterGroup    trees            methodTrees    省略代碼}// 每個http.method （GET,POST,HEAD,PUT等9種）都會構(gòu)建成單獨的前綴樹type methodTree struct {  // 方法: GET,POST等  method string  // 對應方法的前綴樹的根節(jié)點  root   *node}
//GET,POST前綴樹等構(gòu)成的切片type methodTrees []methodTree
type node struct {  // 節(jié)點的當前路徑  path      string  // 子節(jié)點的首字母構(gòu)成的字符串，數(shù)量和位置對應children切片  indices   string  // 子節(jié)點  children  []*node  // 當前匹配到的路由，處理的handler  handlers  HandlersChain  // 統(tǒng)計子節(jié)點優(yōu)先級  priority  uint32  // 節(jié)點類型  nType     nodeType  maxParams uint8  wildChild bool  // 當前節(jié)點的全路徑，從root到當前節(jié)點的全路徑  fullPath  string}

用戶定義路由router := gin.New()router.GET("banner/detail", PkgHandler)router.PrintTrees()router.GET("/game/detail", PkgHandler)router.PrintTrees()router.GET("/geme/detail", PkgHandler)

router.GET 調(diào)用鏈這里提一下HandlerFunc，就是gin常說的中間件，是一個函數(shù)類型，只要實現(xiàn)該函數(shù)類型就可以用作中間件來處理邏輯
func (group *RouterGroup) GET(relativePath string, handlers ...HandlerFunc) IRoutes {  return group.handle(http.MethodGet, relativePath, handlers)}
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()}
func (engine *Engine) addRoute(method, path string, handlers HandlersChain) {  assert1(path[0] == '/', "path must begin with '/'")  assert1(method != "", "HTTP method can not be empty")  assert1(len(handlers) > 0, "there must be at least one handler")
  debugPrintRoute(method, path, handlers)  // 根據(jù)method取出當前方法前綴樹的root  root := engine.trees.get(method)  if root == nil {    root = new(node)    root.fullPath = "/"    engine.trees = append(engine.trees, methodTree{method: method, root: root})  }  // 這里就是構(gòu)建路由前綴樹的邏輯（避免閱讀不友好，這里就不繼續(xù)貼下去了）  root.addRoute(path, handlers)}

先簡述下net/http包處理的整個流程1. 解析數(shù)據(jù)包，解析成http請求協(xié)議，存在http.request， 包裝請求頭，請求體，當前連接conn【read(conn) 讀取數(shù)據(jù)】2. 外部實現(xiàn)handler接口，調(diào)用外部邏輯處理請求（這里外部就是gin）3. 根據(jù)用戶邏輯，返回http響應給客戶端  存在http.response，包裝響應頭，響應體，當前連接conn【write(conn) 返回數(shù)據(jù)】
這是net/http包提供給外部，用于處理http請求的handler接口，只要外部實現(xiàn)了此接口，并且傳遞給http.server.Handler，就可以執(zhí)行用戶handler邏輯，gin的Engine實現(xiàn)了Handler 接口，所以gin就介入了整個http請求流程中的用戶邏輯那部分。即上面的第二點。

type Handler interface {  ServeHTTP(ResponseWriter, *Request)}
func ListenAndServe(addr string, handler Handler) error {  server := &Server{Addr: addr, Handler: handler}  return server.ListenAndServe()}
serverHandler{c.server}.ServeHTTP(w, w.req)
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{}  }    //在這里最終會調(diào)用用戶傳進來的handler接口的實現(xiàn)，并且把rw = http.response，req = http.request 傳遞到gin處理邏輯里面去，這樣gin既能讀取http請求內(nèi)容，也能操作gin輸出到客戶端  handler.ServeHTTP(rw, req)}
// ServeHTTP conforms to the http.Handler interface.// gin.Engine實現(xiàn)了http.Handler接口，可以處理請求func (engine *Engine) ServeHTTP(w http.ResponseWriter, req *http.Request) {  c := engine.pool.Get().(*Context)  c.writermem.reset(w)  c.Request = req  c.reset()
  engine.handleHTTPRequest(c)    //請求完成，放回池中  engine.pool.Put(c)}

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)  }  fmt.Printf("httpMethod: %s, rPath: %s\n", httpMethod, 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        // 根據(jù)請求路徑獲取對應方法樹上的節(jié)點    value := root.getValue(rPath, c.Params, unescape)    if value.handlers != nil {            // 獲取對應節(jié)點上的中間件（即handler）      c.handlers = value.handlers      fmt.Printf("c.handlers: %d\n", len(c.handlers))      c.Params = value.params      c.fullPath = value.fullPath      c.Next()      c.writermem.WriteHeaderNow()      return    }    省略代碼  }        省略代碼}handlers有2種方式1. 在handler中不手動調(diào)用c.next的話，類似于隊列，先進先執(zhí)行2. 如果手動調(diào)用c.next的話，類似于洋蔥模型，包裹剝開概念的執(zhí)行func (c *Context) Next() {    //c.index從-1開始  c.index++  for c.index < int8(len(c.handlers)) {    c.handlers[c.index](c)    c.index++  }}中斷整個調(diào)用鏈，從當前函數(shù)返回func (c *Context) Abort() {    //直接將中間件索引改成最大限制的值，從而退出for循環(huán)    c.index = abortIndex }

serverHandler{c.server}.ServeHTTP(w, w.req)w.cancelCtx()if c.hijacked() {   return}flush數(shù)據(jù), write到connw.finishRequest()