Golang:使用 httprouter 构建 API 服务器

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我 10 个月前开始成为一名 Gopher,没有回头。像许多其他 gopher 一样,我很快发现简单的语言特性对于快速构建快速、可扩展的软件非常有用。当我刚开始学习 Go 时,我正在玩不同的多路复用器(multiplexer),它可以作为 API 服务器使用。如果您像我一样有 Rails 背景,你可能也会在构建 Web 框架提供的所有功能方面遇到困难。回到多路复用器,我发现了 3 个是非常有用的好东西,即 [Gorilla mux](https://github.com/gorilla/mux)、[httprouter](https://github.com/julienschmidt/httprouter) 和 [bone](https://github.com/go-zoo/bone)(按性能从低到高排列)。即使 bone 有最佳性能和更简单的 handler 签名,但对于我来说,它仍然不够成熟,无法用于生产环境。因此,我最终使用了 httprouter。在本教程中,我将使用 httprouter 构建一个简单的 REST API 服务器。 <!-- more --> 如果你想偷懒,只想获取源码,你可以在[这里](https://github.com/gsingharoy/httprouter-tutorial/tree/master/part4)[4]直接检出我的 github 仓库。 让我们开始吧。首先创建一个基本端点: ```go package main import ( "fmt" "log" "net/http" "github.com/julienschmidt/httprouter" ) func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { fmt.Fprint(w, "Welcome!\n") } func main() { router := httprouter.New() router.GET("/", Index) log.Fatal(http.ListenAndServe(":8080", router)) } ``` 在上面的代码段中,`Index` 是一个 handler 函数,需要传入三个参数。 之后,该 handler 将在 `main` 函数中被注册到 GET `/` 路径。 现在编译并运行您的程序,转到 `http:// localhost:8080`,来查看您的 API 服务器。点击[这里](https://github.com/gsingharoy/httprouter-tutorial/tree/master/part1)[1]获取当前代码。 现在我们可以让 API 变得复杂一点。我们现在有一个名为 `Book` 的实体,可以把 `ISDN` 字段作为唯一标识。让我们创建更多的动作,即分表代表着 Index 和 Show 动作的 GET `/books` 和 GET `/books/:isdn`。 我们的 `main.go` 文件此时如下: ```go package main import ( "encoding/json" "fmt" "log" "net/http" "github.com/julienschmidt/httprouter" ) func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { fmt.Fprint(w, "Welcome!\n") } type Book struct { // The main identifier for the Book. This will be unique. ISDN string `json:"isdn"` Title string `json:"title"` Author string `json:"author"` Pages int `json:"pages"` } type JsonResponse struct { // Reserved field to add some meta information to the API response Meta interface{} `json:"meta"` Data interface{} `json:"data"` } type JsonErrorResponse struct { Error *ApiError `json:"error"` } type ApiError struct { Status int16 `json:"status"` Title string `json:"title"` } // A map to store the books with the ISDN as the key // This acts as the storage in lieu of an actual database var bookstore = make(map[string]*Book) // Handler for the books index action // GET /books func BookIndex(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { books := []*Book{} for _, book := range bookstore { books = append(books, book) } response := &JsonResponse{Data: &books} w.Header().Set("Content-Type", "application/json; charset=UTF-8") w.WriteHeader(http.StatusOK) if err := json.NewEncoder(w).Encode(response); err != nil { panic(err) } } // Handler for the books Show action // GET /books/:isdn func BookShow(w http.ResponseWriter, r *http.Request, params httprouter.Params) { isdn := params.ByName("isdn") book, ok := bookstore[isdn] w.Header().Set("Content-Type", "application/json; charset=UTF-8") if !ok { // No book with the isdn in the url has been found w.WriteHeader(http.StatusNotFound) response := JsonErrorResponse{Error: &ApiError{Status: 404, Title: "Record Not Found"}} if err := json.NewEncoder(w).Encode(response); err != nil { panic(err) } } response := JsonResponse{Data: book} if err := json.NewEncoder(w).Encode(response); err != nil { panic(err) } } func main() { router := httprouter.New() router.GET("/", Index) router.GET("/books", BookIndex) router.GET("/books/:isdn", BookShow) // Create a couple of sample Book entries bookstore["123"] = &Book{ ISDN: "123", Title: "Silence of the Lambs", Author: "Thomas Harris", Pages: 367, } bookstore["124"] = &Book{ ISDN: "124", Title: "To Kill a Mocking Bird", Author: "Harper Lee", Pages: 320, } log.Fatal(http.ListenAndServe(":8080", router)) } ``` 如果您现在尝试请求 `GET https:// localhost:8080/books`,您将得到以下响应: ```go { "meta": null, "data": [ { "isdn": "123", "title": "Silence of the Lambs", "author": "Thomas Harris", "pages": 367 }, { "isdn": "124", "title": "To Kill a Mocking Bird", "author": "Harper Lee", "pages": 320 } ] } ``` 我们在 `main` 函数中硬编码了这两个 book 实体。点击[这里](https://github.com/gsingharoy/httprouter-tutorial/tree/master/part2)[2]获取当前阶段的代码。 让我们来重构一下代码。 到目前为止,我们所有的代码都放置在同一个文件中:`main.go`。我们可以把它们移到各个单独的文件中。此时我们有一个目录: ``` . ├── handlers.go ├── main.go ├── models.go └── responses.go ``` 我们把所有与 `JSON` 响应相关的结构体移动到 `responses.go`,将 handler 函数移动到 `Handlers.go`,且将 `Book` 结构体移动到 `models.go`。点击[这里](https://github.com/gsingharoy/httprouter-tutorial/tree/master/part3)[3]查看当前阶段的代码。 现在,我们跳过来写一些测试。在 Go 中,`*_test.go` 文件是用于测试的。因此让我们创建一个 `handlers_test.go`。 ```go package main import ( "net/http" "net/http/httptest" "testing" "github.com/julienschmidt/httprouter" ) func TestBookIndex(t *testing.T) { // Create an entry of the book to the bookstore map testBook := &Book{ ISDN: "111", Title: "test title", Author: "test author", Pages: 42, } bookstore["111"] = testBook // A request with an existing isdn req1, err := http.NewRequest("GET", "/books", nil) if err != nil { t.Fatal(err) } rr1 := newRequestRecorder(req1, "GET", "/books", BookIndex) if rr1.Code != 200 { t.Error("Expected response code to be 200") } // expected response er1 := "{\"meta\":null,\"data\":[{\"isdn\":\"111\",\"title\":\"test title\",\"author\":\"test author\",\"pages\":42}]}\n" if rr1.Body.String() != er1 { t.Error("Response body does not match") } } // Mocks a handler and returns a httptest.ResponseRecorder func newRequestRecorder(req *http.Request, method string, strPath string, fnHandler func(w http.ResponseWriter, r *http.Request, param httprouter.Params)) *httptest.ResponseRecorder { router := httprouter.New() router.Handle(method, strPath, fnHandler) // We create a ResponseRecorder (which satisfies http.ResponseWriter) to record the response. rr := httptest.NewRecorder() // Our handlers satisfy http.Handler, so we can call their ServeHTTP method // directly and pass in our Request and ResponseRecorder. router.ServeHTTP(rr, req) return rr } ``` 我们使用 `httptest` 包的 Recorder 来 mock handler。同样,您也可以为 handler `BookShow` 编写测试。 让我们稍微做些重构。我们仍然把所有路由都定义在了 `main` 函数中,handler 看起来有点臃肿,我们可以做点 DRY,我们仍然在终端中输出一些日志消息,并且可以添加一个 `BookCreate` handler 来创建一个新的 Book。 首先,让我们解决 `handlers.go`。 ```go package main import ( "encoding/json" "fmt" "io" "io/ioutil" "net/http" "github.com/julienschmidt/httprouter" ) func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { fmt.Fprint(w, "Welcome!\n") } // Handler for the books Create action // POST /books func BookCreate(w http.ResponseWriter, r *http.Request, params httprouter.Params) { book := &Book{} if err := populateModelFromHandler(w, r, params, book); err != nil { writeErrorResponse(w, http.StatusUnprocessableEntity, "Unprocessible Entity") return } bookstore[book.ISDN] = book writeOKResponse(w, book) } // Handler for the books index action // GET /books func BookIndex(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { books := []*Book{} for _, book := range bookstore { books = append(books, book) } writeOKResponse(w, books) } // Handler for the books Show action // GET /books/:isdn func BookShow(w http.ResponseWriter, r *http.Request, params httprouter.Params) { isdn := params.ByName("isdn") book, ok := bookstore[isdn] if !ok { // No book with the isdn in the url has been found writeErrorResponse(w, http.StatusNotFound, "Record Not Found") return } writeOKResponse(w, book) } // Writes the response as a standard JSON response with StatusOK func writeOKResponse(w http.ResponseWriter, m interface{}) { w.Header().Set("Content-Type", "application/json; charset=UTF-8") w.WriteHeader(http.StatusOK) if err := json.NewEncoder(w).Encode(&JsonResponse{Data: m}); err != nil { writeErrorResponse(w, http.StatusInternalServerError, "Internal Server Error") } } // Writes the error response as a Standard API JSON response with a response code func writeErrorResponse(w http.ResponseWriter, errorCode int, errorMsg string) { w.Header().Set("Content-Type", "application/json; charset=UTF-8") w.WriteHeader(errorCode) json. NewEncoder(w). Encode(&JsonErrorResponse{Error: &ApiError{Status: errorCode, Title: errorMsg}}) } //Populates a model from the params in the Handler func populateModelFromHandler(w http.ResponseWriter, r *http.Request, params httprouter.Params, model interface{}) error { body, err := ioutil.ReadAll(io.LimitReader(r.Body, 1048576)) if err != nil { return err } if err := r.Body.Close(); err != nil { return err } if err := json.Unmarshal(body, model); err != nil { return err } return nil } ``` 我创建了两个函数,`writeOKResponse` 用于将 `StatusOK` 写入响应,其返回一个 model 或一个 model slice,`writeErrorResponse` 将在发生预期或意外错误时将 `JSON` 错误作为响应。像任何一个优秀的 gopher 一样,我们不应该 panic。我还添加了一个名为 `populateModelFromHandler` 的函数,它将内容从 body 中解析成所需的任何 model(struct)。在这种情况下,我们在 `BookCreate` handler 中使用它来填充一个 `Book`。 现在,我们来看看日志。我们简单地创建一个 `Logger` 函数,它包装了 handler 函数,并在执行 handler 函数之前和之后打印日志消息。 ```go package main import ( "log" "net/http" "time" "github.com/julienschmidt/httprouter" ) // A Logger function which simply wraps the handler function around some log messages func Logger(fn func(w http.ResponseWriter, r *http.Request, param httprouter.Params)) func(w http.ResponseWriter, r *http.Request, param httprouter.Params) { return func(w http.ResponseWriter, r *http.Request, param httprouter.Params) { start := time.Now() log.Printf("%s %s", r.Method, r.URL.Path) fn(w, r, param) log.Printf("Done in %v (%s %s)", time.Since(start), r.Method, r.URL.Path) } } ``` 我们来看看路由。首先,在一个地方集中定义所有路由,比如 `routes.go`。 ```go package main import "github.com/julienschmidt/httprouter" /* Define all the routes here. A new Route entry passed to the routes slice will be automatically translated to a handler with the NewRouter() function */ type Route struct { Name string Method string Path string HandlerFunc httprouter.Handle } type Routes []Route func AllRoutes() Routes { routes := Routes{ Route{"Index", "GET", "/", Index}, Route{"BookIndex", "GET", "/books", BookIndex}, Route{"Bookshow", "GET", "/books/:isdn", BookShow}, Route{"Bookshow", "POST", "/books", BookCreate}, } return routes } ``` 让我们创建一个 `NewRouter` 函数,它可以在 `main` 函数中调用,它读取上面定义的所有路由,并返回一个可用的 `httprouter.Router`。因此创建一个文件 `router.go`。我们还将使用新创建的 `Logger` 函数来包装 handler。 ```go package main import "github.com/julienschmidt/httprouter" //Reads from the routes slice to translate the values to httprouter.Handle func NewRouter(routes Routes) *httprouter.Router { router := httprouter.New() for _, route := range routes { var handle httprouter.Handle handle = route.HandlerFunc handle = Logger(handle) router.Handle(route.Method, route.Path, handle) } return router } ``` 您的目录此时应该像这样: ``` . ├── handlers.go ├── handlers_test.go ├── logger.go ├── main.go ├── models.go ├── responses.go ├── router.go └── routes.go ``` 在[这里](https://github.com/gsingharoy/httprouter-tutorial/tree/master/part4)[4]查看完整代码。 这应该可以让你开始编写你自己的 API 服务器了。 你当然需要把你的功能放在不同的包中,所以一个好办法就是: ``` . ├── LICENSE ├── README.md ├── handlers │ ├── books_test.go │ └── books.go ├── models │ ├── book.go │ └── * ├── store │ ├── * └── lib | ├── * ├── main.go ├── router.go ├── rotes.go ``` 如果您有一个大的单体服务器,您还可以将 `handlers`、`models` 和所有路由功能都放在另一个名为 `app` 的包中。只要记住,go 不像 Java 或 Scala 那样可以有循环的包调用。因此你必须格外小心您的包结构。 这就是全部内容,希望本教程能对您有用。干杯! ## 注 - [1] https://github.com/gsingharoy/httprouter-tutorial/tree/master/part1 - [2] https://github.com/gsingharoy/httprouter-tutorial/tree/master/part2 - [3] https://github.com/gsingharoy/httprouter-tutorial/tree/master/part3 - [4] https://github.com/gsingharoy/httprouter-tutorial/tree/master/part4 - [Gorilla mux] https://github.com/gorilla/mux - [httprouter] https://github.com/julienschmidt/httprouter - [bone] https://github.com/go-zoo/bone > [https://medium.com/@gauravsingharoy/build-your-first-api-server-with-httprouter-in-golang-732b7b01f6ab](https://medium.com/@gauravsingharoy/build-your-first-api-server-with-httprouter-in-golang-732b7b01f6ab) > 作者:Gaurav Singha Roy > 译者:oopsguy.com

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