httprouter
httprouter 是一个高性能、可扩展的HTTP路由，上面我们列举的net/http默认路由的不足，都被httprouter 实现，我们先用一个例子，认识下 httprouter 这个强大的 HTTP 路由。
安装：
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go get -u github.com/julienschmidt/httprouter
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在这个例子中，首先通过httprouter.New()生成了一个*Router路由指针,然后使用GET方法注册一个适配/路径的Index函数，最后*Router作为参数传给ListenAndServe函数启动HTTP服务即可。
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package main
import (
"log"
"net/http"
"github.com/julienschmidt/httprouter"
)
func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
w.Write([]byte("Index"))
}
func main() {
router := httprouter.New()
router.GET("/", Index)
log.Fatal(http.ListenAndServe(":8080", router))
}
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httprouter 为所有的HTTP Method 提供了快捷的使用方式，只需要调用对应的方法即可。
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func (r *Router) GET(path string, handle Handle) {
r.Handle("GET", path, handle)
}
func (r *Router) HEAD(path string, handle Handle) {
r.Handle("HEAD", path, handle)
}
func (r *Router) OPTIONS(path string, handle Handle) {
r.Handle("OPTIONS", path, handle)
}
func (r *Router) POST(path string, handle Handle) {
r.Handle("POST", path, handle)
}
func (r *Router) PUT(path string, handle Handle) {
r.Handle("PUT", path, handle)
}
func (r *Router) PATCH(path string, handle Handle) {
r.Handle("PATCH", path, handle)
}
func (r *Router) DELETE(path string, handle Handle) {
r.Handle("DELETE", path, handle)
}
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现代的API，基本上都是Restful API，httprouter提供的命名参数的支持，可以很方便的帮助我们开发Restful API。比如我们设计的API/user/flysnow，这这样一个URL，可以查看flysnow这个用户的信息，如果要查看其他用户的，比如zhangsan,我们只需要访问API/user/zhangsan即可。
URL包括两种匹配模式：/user/:name精确匹配、/user/*name匹配所有的模式。
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package main
import (
"github.com/julienschmidt/httprouter"
"net/http"
"log"
"fmt"
)
func main() {
router:=httprouter.New()
router.GET("/MainData", func (w http.ResponseWriter,r *http.Request,_ httprouter.Params) {
w.Write([]byte("default get"))
})
router.POST("/MainData",func (w http.ResponseWriter,r *http.Request,_ httprouter.Params) {
w.Write([]byte("default post"))
})
//精确匹配
router.GET("/user/name",func (w http.ResponseWriter,r *http.Request,p httprouter.Params) {
w.Write([]byte("user name:"+p.ByName("name")))
})
//匹配所有
router.GET("/employee/*name",func (w http.ResponseWriter,r *http.Request,p httprouter.Params) {
w.Write([]byte("employee name:"+p.ByName("name")))
})
http.ListenAndServe(":8081", router)
}
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Handler处理链处理不同二级域名
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package main
import (
"fmt"
"log"
"net/http"
"github.com/julienschmidt/httprouter"
)
type HostMap map[string]http.Handler
func (hs HostMap) ServeHTTP(w http.ResponseWriter, r *http.Request) {
fmt.Println("222")
//根据域名获取对应的Handler路由，然后调用处理（分发机制）
if handler := hs[r.Host]; handler != nil {
handler.ServeHTTP(w, r)
} else {
http.Error(w, "Forbidden", 403)
}
}
func main() {
userRouter := httprouter.New()
userRouter.GET("/", func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
w.Write([]byte("play"))
})
dataRouter := httprouter.New()
dataRouter.GET("/", func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
w.Write([]byte("tool"))
})
//分别用于处理不同的二级域名
hs := make(HostMap)
hs["user.localhost:12345"] = userRouter
hs["data.localhost:12345"] = dataRouter
log.Fatal(http.ListenAndServe(":12345", hs))
}
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httprouter提供了很方便的静态文件服务，可以把一个目录托管在服务器上，以供访问。
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router.ServeFiles("/static/*filepath",http.Dir("./"))
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使用ServeFiles需要注意的是，第一个参数路径，必须要以/*filepath，因为要获取我们要访问的路径信息。
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func (r *Router) ServeFiles(path string, root http.FileSystem) {
if len(path) < 10 || path[len(path)-10:] != "/*filepath" {
panic("path must end with /*filepath in path '" + path + "'")
}
fileServer := http.FileServer(root)
r.GET(path, func(w http.ResponseWriter, req *http.Request, ps Params) {
req.URL.Path = ps.ByName("filepath")
fileServer.ServeHTTP(w, req)
})
}
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例子：
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package main
import (
"log"
"net/http"
"github.com/julienschmidt/httprouter"
)
func main() {
router := httprouter.New()
//访问静态文件
router.ServeFiles("/static/*filepath", http.Dir("./files"))
log.Fatal(http.ListenAndServe(":8080", router))
}
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httprouter 异常捕获，httprouter允许使用者，设置PanicHandler用于处理HTTP请求中发生的panic。
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package main
import (
"fmt"
"log"
"net/http"
"github.com/julienschmidt/httprouter"
)
func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
panic("error")
}
func main() {
router := httprouter.New()
router.GET("/", Index)
//捕获异常
router.PanicHandler = func(w http.ResponseWriter, r *http.Request, v interface{}) {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "error:%s", v)
}
log.Fatal(http.ListenAndServe(":8080", router))
}
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httprouter还有不少有用的小功能，比如对404进行处理，我们通过设置Router.NotFound来实现，我们看看Router这个结构体的配置，可以发现更多有用的功能。
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type Router struct {
//是否通过重定向，给路径自定加斜杠
RedirectTrailingSlash bool
//是否通过重定向，自动修复路径，比如双斜杠等自动修复为单斜杠
RedirectFixedPath bool
//是否检测当前请求的方法被允许
HandleMethodNotAllowed bool
//是否自定答复OPTION请求
HandleOPTIONS bool
//404默认处理
NotFound http.Handler
//不被允许的方法默认处理
MethodNotAllowed http.Handler
//异常统一处理
PanicHandler func(http.ResponseWriter, *http.Request, interface{})
}
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