Writer{c}, 4<<10)
for {
w, err := c.readRequest()
if c.r.remain != c.server.initialReadLimitSize() {
// If we read any bytes off the wire, we're active.
c.setState(c.rwc, StateActive)
}
if err != nil {
if err == errTooLarge {
// Their HTTP client may or may not be
// able to read this if we're
// responding to them and hanging up
// while they're still writing their
// request. Undefined behavior.
io.WriteString(c.rwc, "HTTP/1.1 431 Request Header Fields Too Large\r\nContent-Type: text/plain\r\nConnection: close\r\n\r\n431 Request Header Fields Too Large")
c.closeWriteAndWait()
return
}
if err == io.EOF {
return // don't reply
}
if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
return // don't reply
}
var publicErr string
if v, ok := err.(badRequestError); ok {
publicErr = ": " + string(v)
}
io.WriteString(c.rwc, "HTTP/1.1 400 Bad Request\r\nContent-Type: text/plain\r\nConnection: close\r\n\r\n400 Bad Request"+publicErr)
return
}
// Expect 100 Continue support
req := w.req
if req.expectsContinue() {
if req.ProtoAtLeast(1, 1) && req.ContentLength != 0 {
// Wrap the Body reader with one that replies on the connection
req.Body = &expectContinueReader{readCloser: req.Body, resp: w}
}
} else if req.Header.get("Expect") != "" {
w.sendExpectationFailed()
return
}
// HTTP cannot have multiple simultaneous active requests.[*]
// Until the server replies to this request, it can't read another,
// so we might as well run the handler in this goroutine.
// [*] Not strictly true: HTTP pipelining. We could let them all process
// in parallel even if their responses need to be serialized.
serverHandler{c.server}.ServeHTTP(w, w.req)
if c.hijacked() {
return
}
w.finishRequest()
if !w.shouldReuseConnection() {
if w.requestBodyLimitHit || w.closedRequestBodyEarly() {
c.closeWriteAndWait()
}
return
}
c.setState(c.rwc, StateIdle)
}
}
这个方法稍微有点长，其他的先不管，上边红色加粗标注的代码就是查找相应Handler的部分，这里用的是一个serverHandler，并调用了它的ServeHTTP函数。
type serverHandler struct {
srv *Server
}
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{}
}
handler.ServeHTTP(rw, req)
}
从上边的代码可以看出，当handler为空时，handler被设置为DefaultServeMux，就是一开始注册时使用的路由表。如果一层一层的往上翻，就会看到sh.srv.Handler在ListenAndServe函数中的第二个参数，而这个参数我们传入的就是一个nil空值，所以我们使用的路由表就是这个DefaultServeMux。当然我们也可以自己传入一个自定义的ServMux，但是后续的查找过程都是一样的，具体的例子可以参考Go-HTTP。到这里又出现了跟上边一样的情况，虽然实际用的时候是按照Handler使用的，但实际上是一个ServeMux，所以最后调用的ServeHTTP函数，我们还是得看ServeMux的具体实现。
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)
h.ServeHTTP(w, r)
}
具体的实现就是根据传入的Request，解析出URI来，然后从其内部的map中找到相应的Handler并返回，最后调用ServeHTTP，也就是上边提到的我们注册时传入的sayHello方法（上边也提过，ServeHTTP的具体实现，就是调