gin 是 golang 中最流行的 web 框架，拥有高性能的路由，官网中介绍的主要特点包括快速、支持中间件、crash 处理、json 验证、支持路由组等，这些特性可以类比 node 的 koa 框架。
快速开始
安装：
go get -u github.com/gin-gonic/gin
返回一个 json 的路由：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/someJson", func(c *gin.Context) {
data := map[string]interface{}{
"lang": "go lang",
"tag": "<br>",
}
c.JSON(http.StatusOK, data)
})
r.Run(":8000")
}
其中 gin.Default 是默认开启 logger 和 recovery 两个中间件，从源码中可以看到，相当于是调用 New 函数之后使用 Use 开启两个中间件：
改写成使用 New 方法就是：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.New()
r.Use(gin.Logger(), gin.Recovery())
r.GET("/someJson", func(c *gin.Context) {
data := map[string]interface{}{
"lang": "go lang",
"tag": "<br>",
}
c.JSON(http.StatusOK, data)
})
r.Run(":8000")
}
路由和路由组
Gin 支持 get、post、patch、delete、put、options、head、any，其中 any 是支持get、post、patch、delete、put、options、head 这7种方法，gin 提供了这些 http 方法的的大写形式的方法，从 gin 的源码中可以看到这些是 RouterGroup 结构体的方法：
这些方法都是 Handle 的快捷方法，这个从源码可以看到都同样使用了 group.handle 方法，Handle 中对传入的 httpMethod 方法做了字符串校验：
我们将上面的 r.GET 修改为 Handle 方法，如下：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.New()
r.Use(gin.Logger(), gin.Recovery())
r.Handle(http.MethodGet, "/someJson", func(c *gin.Context) {
data := map[string]interface{}{
"lang": "go lang",
"tag": "<br>",
}
c.JSON(http.StatusOK, data)
})
r.Run(":8000")
}
在实际开发中，我们经常有对 api 版本、业务模块划分路由的场景，在 gin 中可以通过路由组来实现，即 Group 方法：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
v1 := r.Group("/api/v1")
v1.GET("/getUser", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"name": "golang",
"id": "1",
})
})
r.Run(":8000")
}
从源码中可以看到 Group 方法返回了一个新的 RouterGroup，同时将对应的 routePath 计算作为一个 basePath
在处理路由的时候 handle 方法会 调用 calculateAbsolutePath 方法计算出最后的路由路径
路由参数
Gin 的路由基于的是 httprouter，和 koa 一样以 :param 的方式作为一个路由参数，通过 context 的 Param 方法获取对应的值，如：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user/:id", func(c *gin.Context) {
id := c.Param("id")
c.JSON(http.StatusOK, gin.H{
"user": id,
})
})
r.Run(":8000")
}
通过源码我们可以看到是通过 c.Params.ByName 获取的，c.Params 本质上是一个存储参数的 slice
路由参数还支持以 * 开头匹配所有，如：
package main
import (
"fmt"
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/article/*id", func(c *gin.Context) {
id := c.Param("id")
c.JSON(http.StatusOK, gin.H{
"article": id,
})
})
r.Run(":8000")
}
这段代码可以匹配以下所有路由：
/aritcle/123
/article/123/info
/aritcle/123/author/info
Get 和 Post 参数
在开发中最常见的就是通过 get（query string）、post 参数（http body）来向服务端传递数据，gin 通过 Context 的 Query 获取对应的 get 参数：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user", func(c *gin.Context) {
id := c.Query("id")
c.JSON(http.StatusOK, gin.H{
"id": id,
})
})
r.Run(":8000")
}
在源码中我们可以看到调用的是 context 的 GetQuery 方法：
query 在 gin 内部是通过一个 map 来存储，map 定义为 map[string][]string，本质上是通过 context 的 c.Request.URL.Query() 方法拿到的：
在 gin 内部是通过 parseQuery 方法来解析的，从返回值也可以看出是一个以 string 为 key，string 数组为值的 map
如果想要为 query 不存在时设置一个默认值，可以使用 DefaultQuery 方法，在这个方法内部也是使用 GetQuery 方法，当不存在时使用默认值
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user", func(c *gin.Context) {
id := c.DefaultQuery("id", "456")
c.JSON(http.StatusOK, gin.H{
"id": id,
})
})
r.Run(":8000")
}
向服务端发数据的时候常常使用 post 方法，以 form-data 的形式存放在 http body 内，在 gin 中可以通过 PostForm 方法获取对应的值：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.POST("/user", func(c *gin.Context) {
id := c.PostForm("id")
c.JSON(http.StatusOK, gin.H{
"code": 200,
"id": id,
})
})
r.Run(":8000")
}
和 query 类似，可以通过 DefaultPostForm 来设置对应的默认值，内部都是通过 GetPostForm 方法来获取的：
id := c.DefaultPostForm("id", "456")
cookie 和 http header
开发过程中常常需要获取和设置 cookie，可以通过 c.Cookie 获取对应的 cookie 值，使用 c.SetCookie 来设置 cookie：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user", func(c *gin.Context) {
session, _ := c.Cookie("session")
c.SetCookie("site_cookie", "cookie1", 3600, "/", "localhost", false, true)
c.JSON(http.StatusOK, gin.H{
"code": 200,
"session": session,
})
})
r.Run(":8000")
}
获取 cookie 内部也是通过 c.Request.Cookie 来获取的，c.Request.Cookie 会读取解析 http 头 cookie 字段：
Http header 可以通过 c.GetHeader(key) 的形式获取：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user", func(c *gin.Context) {
lang := c.GetHeader("lang")
c.JSON(http.StatusOK, gin.H{
"code": 200,
"lang": lang,
})
})
r.Run(":8000")
}
本质上是通过 request 的 header.get 方法获取的，即 c.Request.Header.Get，源码如下：
设置 HTTP 响应头通过 Header 方法即可：
c.Header("user", "golang")
实际上是通过 http 包的 Header struct 来设置的：
重定向
gin 框架的重定向 context 下有 Redirect 方法帮助我们重定向，也可以直接修改 context request 的 url 信息，然后继续处理 context：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/info", func(c *gin.Context) {
c.Redirect(http.StatusMovedPermanently, "/user")
})
r.GET("/article", func(c *gin.Context) {
c.Request.URL.Path = "/user"
r.HandleContext(c)
})
r.GET("/user", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"code": 200,
"data": "user",
})
})
r.Run(":8000")
}
Redirect 本质上也是调用的 http 包的 Redirect 方法：
静态资源和模版引擎
设置静态资源和模版引擎是一个 web 服务器最基本的能力，gin 通过路由的 Static、StaticFS、StaticFile 三种方法设置：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.Static("/", "./public")
r.StaticFile("/", "./public")
r.StaticFS("/", http.Dir("./public"))
r.Run(":8000")
}
Static 本质上内部也是通过 StaticFS 方法来实现的：
golang 有一个模版引擎标准库 http/template，gin 内部默认也是使用这个标准库，这个库和我们常用的模版引擎类似，使用胡子表达式作为变量，gin 中使用 LoadHTMLGlob 方法加载模版，使用 c.HTML 表示使用模版引擎处理，源代码可以在 gin 的 render/html.go 中：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.LoadHTMLGlob("./template/*")
r.GET("/index", func(c *gin.Context) {
c.HTML(http.StatusOK, "index.tmpl", gin.H{
"title": "golang",
})
})
r.Run(":8000")
}
<html>
<h1>
{{ .title }}
</h1>
</html>
Context
gin 的 context 贯穿一次 http 请求的全流程，可以类比 koa 的 context，context 也是 gin 中最核心的一个对象，这个对象含有的字段从源码中可以看到有以下属性：
/ Context is the most important part of gin. It allows us to pass variables between middleware,
// manage the flow, validate the JSON of a request and render a JSON response for example.
type Context struct {
writermem responseWriter
Request *http.Request
Writer ResponseWriter
Params Params
handlers HandlersChain
index int8
fullPath string
engine *Engine
params *Params
// 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
}
上面对 query、postForm、param 、header、cookie 等的操作都是挂在 context 上的，context 也提供了基本的元数据存取，Get 和 Set，这样我们可以把需要的（尤其是跨中间件使用的）数据挂在 context 上，本质上是存储在 c.Keys 上的：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func main() {
r := gin.Default()
r.GET("/user", func(c *gin.Context) {
c.Set("key", "value")
val, _ := c.Get("key")
c.JSON(http.StatusOK, gin.H{
"code": 200,
"key": val,
})
})
r.Run(":8000")
}
除了 Get 存储外，gin 还内置了 MustGet（不存在就出发 panic）、对类型断言后的取值如 GetString、GetBool、GetInt 等
对元数据存取的方法有以下：
/************************************/
/******** METADATA MANAGEMENT********/
/************************************/
func (c *Context) Set(key string, value interface{}) {}
// Get returns the value for the given key, ie: (value, true).
// If the value does not exists it returns (nil, false)
func (c *Context) Get(key string) (value interface{}, exists bool) {}
// MustGet returns the value for the given key if it exists, otherwise it panics.
func (c *Context) MustGet(key string) interface{} {}
// GetString returns the value associated with the key as a string.
func (c *Context) GetString(key string) (s string) {}
// GetBool returns the value associated with the key as a boolean.
func (c *Context) GetBool(key string) (b bool) {}
// GetInt returns the value associated with the key as an integer.
func (c *Context) GetInt(key string) (i int) {}
// GetInt64 returns the value associated with the key as an integer.
func (c *Context) GetInt64(key string) (i64 int64) {}
// GetUint returns the value associated with the key as an unsigned integer.
func (c *Context) GetUint(key string) (ui uint) {
}
// GetUint64 returns the value associated with the key as an unsigned integer.
func (c *Context) GetUint64(key string) (ui64 uint64) {}
// GetFloat64 returns the value associated with the key as a float64.
func (c *Context) GetFloat64(key string) (f64 float64) {}
// GetTime returns the value associated with the key as time.
func (c *Context) GetTime(key string) (t time.Time) {}
// GetDuration returns the value associated with the key as a duration.
func (c *Context) GetDuration(key string) (d time.Duration) {}
// GetStringSlice returns the value associated with the key as a slice of strings.
func (c *Context) GetStringSlice(key string) (ss []string) {}
// GetStringMap returns the value associated with the key as a map of interfaces.
func (c *Context) GetStringMap(key string) (sm map[string]interface{}) {}
// GetStringMapString returns the value associated with the key as a map of strings.
func (c *Context) GetStringMapString(key string) (sms map[string]string) {}
// GetStringMapStringSlice returns the value associated with the key as a map to a slice of strings.
func (c *Context) GetStringMapStringSlice(key string) (smss map[string][]string) {}
gin 中把对 query、postForm、param 等请求数据称为 Input Data，从 gin 的源码中可以看到这部分的方法主要有对 query、postForm、param 等信息的获取和参数绑定的方法，源码如下：
/************************************/
/************ INPUT DATA ************/
/************************************/
// Param returns the value of the URL param.
// It is a shortcut for c.Params.ByName(key)
// router.GET("/user/:id", func(c *gin.Context) {
// // a GET request to /user/john
// id := c.Param("id") // id == "john"
// })
func (c *Context) Param(key string) string {
return c.Params.ByName(key)
}
// Query returns the keyed url query value if it exists,
// otherwise it returns an empty string `("")`.
// It is shortcut for `c.Request.URL.Query().Get(key)`
// GET /path?id=1234&name=Manu&value=
// c.Query("id") == "1234"
// c.Query("name") == "Manu"
// c.Query("value") == ""
// c.Query("wtf") == ""
func (c *Context) Query(key string) string {
value, _ := c.GetQuery(key)
return value
}
// DefaultQuery returns the keyed url query value if it exists,
// otherwise it returns the specified defaultValue string.
// See: Query() and GetQuery() for further information.
// GET /?name=Manu&lastname=
// c.DefaultQuery("name", "unknown") == "Manu"
// c.DefaultQuery("id", "none") == "none"
// c.DefaultQuery("lastname", "none") == ""
func (c *Context) DefaultQuery(key, defaultValue string) string {
if value, ok := c.GetQuery(key); ok {
return value
}
return defaultValue
}
// GetQuery is like Query(), it returns the keyed url query value
// if it exists `(value, true)` (even when the value is an empty string),
// otherwise it returns `("", false)`.
// It is shortcut for `c.Request.URL.Query().Get(key)`
// GET /?name=Manu&lastname=
// ("Manu", true) == c.GetQuery("name")
// ("", false) == c.GetQuery("id")
// ("", true) == c.GetQuery("lastname")
func (c *Context) GetQuery(key string) (string, bool) {
if values, ok := c.GetQueryArray(key); ok {
return values[0], ok
}
return "", false
}
// QueryArray returns a slice of strings for a given query key.
// The length of the slice depends on the number of params with the given key.
func (c *Context) QueryArray(key string) []string {
values, _ := c.GetQueryArray(key)
return values
}
func (c *Context) initQueryCache() {
if c.queryCache == nil {
if c.Request != nil {
c.queryCache = c.Request.URL.Query()
} else {
c.queryCache = url.Values{}
}
}
}
// GetQueryArray returns a slice of strings for a given query key, plus
// a boolean value whether at least one value exists for the given key.
func (c *Context) GetQueryArray(key string) ([]string, bool) {
c.initQueryCache()
if values, ok := c.queryCache[key]; ok && len(values) > 0 {
return values, true
}
return []string{}, false
}
// QueryMap returns a map for a given query key.
func (c *Context) QueryMap(key string) map[string]string {
dicts, _ := c.GetQueryMap(key)
return dicts
}
// GetQueryMap returns a map for a given query key, plus a boolean value
// whether at least one value exists for the given key.
func (c *Context) GetQueryMap(key string) (map[string]string, bool) {
c.initQueryCache()
return c.get(c.queryCache, key)
}
// PostForm returns the specified key from a POST urlencoded form or multipart form
// when it exists, otherwise it returns an empty string `("")`.
func (c *Context) PostForm(key string) string {
value, _ := c.GetPostForm(key)
return value
}
// DefaultPostForm returns the specified key from a POST urlencoded form or multipart form
// when it exists, otherwise it returns the specified defaultValue string.
// See: PostForm() and GetPostForm() for further information.
func (c *Context) DefaultPostForm(key, defaultValue string) string {
if value, ok := c.GetPostForm(key); ok {
return value
}
return defaultValue
}
// GetPostForm is like PostForm(key). It returns the specified key from a POST urlencoded
// form or multipart form when it exists `(value, true)` (even when the value is an empty string),
// otherwise it returns ("", false).
// For example, during a PATCH request to update the user's email:
// email=mail@example.com --> ("mail@example.com", true) := GetPostForm("email") // set email to "mail@example.com"
// email= --> ("", true) := GetPostForm("email") // set email to ""
// --> ("", false) := GetPostForm("email") // do nothing with email
func (c *Context) GetPostForm(key string) (string, bool) {
if values, ok := c.GetPostFormArray(key); ok {
return values[0], ok
}
return "", false
}
// PostFormArray returns a slice of strings for a given form key.
// The length of the slice depends on the number of params with the given key.
func (c *Context) PostFormArray(key string) []string {
values, _ := c.GetPostFormArray(key)
return values
}
func (c *Context) initFormCache() {
if c.formCache == nil {
c.formCache = make(url.Values)
req := c.Request
if err := req.ParseMultipartForm(c.engine.MaxMultipartMemory); err != nil {
if err != http.ErrNotMultipart {
debugPrint("error on parse multipart form array: %v", err)
}
}
c.formCache = req.PostForm
}
}
// GetPostFormArray returns a slice of strings for a given form key, plus
// a boolean value whether at least one value exists for the given key.
func (c *Context) GetPostFormArray(key string) ([]string, bool) {
c.initFormCache()
if values := c.formCache[key]; len(values) > 0 {
return values, true
}
return []string{}, false
}
// PostFormMap returns a map for a given form key.
func (c *Context) PostFormMap(key string) map[string]string {
dicts, _ := c.GetPostFormMap(key)
return dicts
}
// GetPostFormMap returns a map for a given form key, plus a boolean value
// whether at least one value exists for the given key.
func (c *Context) GetPostFormMap(key string) (map[string]string, bool) {
c.initFormCache()
return c.get(c.formCache, key)
}
// get is an internal method and returns a map which satisfy conditions.
func (c *Context) get(m map[string][]string, key string) (map[string]string, bool) {
dicts := make(map[string]string)
exist := false
for k, v := range m {
if i := strings.IndexByte(k, '['); i >= 1 && k[0:i] == key {
if j := strings.IndexByte(k[i+1:], ']'); j >= 1 {
exist = true
dicts[k[i+1:][:j]] = v[0]
}
}
}
return dicts, exist
}
// FormFile returns the first file for the provided form key.
func (c *Context) FormFile(name string) (*multipart.FileHeader, error) {
if c.Request.MultipartForm == nil {
if err := c.Request.ParseMultipartForm(c.engine.MaxMultipartMemory); err != nil {
return nil, err
}
}
f, fh, err := c.Request.FormFile(name)
if err != nil {
return nil, err
}
f.Close()
return fh, err
}
// MultipartForm is the parsed multipart form, including file uploads.
func (c *Context) MultipartForm() (*multipart.Form, error) {
err := c.Request.ParseMultipartForm(c.engine.MaxMultipartMemory)
return c.Request.MultipartForm, err
}
// SaveUploadedFile uploads the form file to specific dst.
func (c *Context) SaveUploadedFile(file *multipart.FileHeader, dst string) error {
src, err := file.Open()
if err != nil {
return err
}
defer src.Close()
out, err := os.Create(dst)
if err != nil {
return err
}
defer out.Close()
_, err = io.Copy(out, src)
return err
}
// Bind checks the Content-Type to select a binding engine automatically,
// Depending the "Content-Type" header different bindings are used:
// "application/json" --> JSON binding
// "application/xml" --> XML binding
// otherwise --> returns an error.
// It parses the request's body as JSON if Content-Type == "application/json" using JSON or XML as a JSON input.
// It decodes the json payload into the struct specified as a pointer.
// It writes a 400 error and sets Content-Type header "text/plain" in the response if input is not valid.
func (c *Context) Bind(obj interface{}) error {
b := binding.Default(c.Request.Method, c.ContentType())
return c.MustBindWith(obj, b)
}
// BindJSON is a shortcut for c.MustBindWith(obj, binding.JSON).
func (c *Context) BindJSON(obj interface{}) error {
return c.MustBindWith(obj, binding.JSON)
}
// BindXML is a shortcut for c.MustBindWith(obj, binding.BindXML).
func (c *Context) BindXML(obj interface{}) error {
return c.MustBindWith(obj, binding.XML)
}
// BindQuery is a shortcut for c.MustBindWith(obj, binding.Query).
func (c *Context) BindQuery(obj interface{}) error {
return c.MustBindWith(obj, binding.Query)
}
// BindYAML is a shortcut for c.MustBindWith(obj, binding.YAML).
func (c *Context) BindYAML(obj interface{}) error {
return c.MustBindWith(obj, binding.YAML)
}
// BindHeader is a shortcut for c.MustBindWith(obj, binding.Header).
func (c *Context) BindHeader(obj interface{}) error {
return c.MustBindWith(obj, binding.Header)
}
// BindUri binds the passed struct pointer using binding.Uri.
// It will abort the request with HTTP 400 if any error occurs.
func (c *Context) BindUri(obj interface{}) error {
if err := c.ShouldBindUri(obj); err != nil {
c.AbortWithError(http.StatusBadRequest, err).SetType(ErrorTypeBind) // nolint: errcheck
return err
}
return nil
}
// MustBindWith binds the passed struct pointer using the specified binding engine.
// It will abort the request with HTTP 400 if any error occurs.
// See the binding package.
func (c *Context) MustBindWith(obj interface{}, b binding.Binding) error {
if err := c.ShouldBindWith(obj, b); err != nil {
c.AbortWithError(http.StatusBadRequest, err).SetType(ErrorTypeBind) // nolint: errcheck
return err
}
return nil
}
// ShouldBind checks the Content-Type to select a binding engine automatically,
// Depending the "Content-Type" header different bindings are used:
// "application/json" --> JSON binding
// "application/xml" --> XML binding
// otherwise --> returns an error
// It parses the request's body as JSON if Content-Type == "application/json" using JSON or XML as a JSON input.
// It decodes the json payload into the struct specified as a pointer.
// Like c.Bind() but this method does not set the response status code to 400 and abort if the json is not valid.
func (c *Context) ShouldBind(obj interface{}) error {
b := binding.Default(c.Request.Method, c.ContentType())
return c.ShouldBindWith(obj, b)
}
// ShouldBindJSON is a shortcut for c.ShouldBindWith(obj, binding.JSON).
func (c *Context) ShouldBindJSON(obj interface{}) error {
return c.ShouldBindWith(obj, binding.JSON)
}
// ShouldBindXML is a shortcut for c.ShouldBindWith(obj, binding.XML).
func (c *Context) ShouldBindXML(obj interface{}) error {
return c.ShouldBindWith(obj, binding.XML)
}
// ShouldBindQuery is a shortcut for c.ShouldBindWith(obj, binding.Query).
func (c *Context) ShouldBindQuery(obj interface{}) error {
return c.ShouldBindWith(obj, binding.Query)
}
// ShouldBindYAML is a shortcut for c.ShouldBindWith(obj, binding.YAML).
func (c *Context) ShouldBindYAML(obj interface{}) error {
return c.ShouldBindWith(obj, binding.YAML)
}
// ShouldBindHeader is a shortcut for c.ShouldBindWith(obj, binding.Header).
func (c *Context) ShouldBindHeader(obj interface{}) error {
return c.ShouldBindWith(obj, binding.Header)
}
// ShouldBindUri binds the passed struct pointer using the specified binding engine.
func (c *Context) ShouldBindUri(obj interface{}) error {
m := make(map[string][]string)
for _, v := range c.Params {
m[v.Key] = []string{v.Value}
}
return binding.Uri.BindUri(m, obj)
}
// ShouldBindWith binds the passed struct pointer using the specified binding engine.
// See the binding package.
func (c *Context) ShouldBindWith(obj interface{}, b binding.Binding) error {
return b.Bind(c.Request, obj)
}
// ShouldBindBodyWith is similar with ShouldBindWith, but it stores the request
// body into the context, and reuse when it is called again.
//
// NOTE: This method reads the body before binding. So you should use
// ShouldBindWith for better performance if you need to call only once.
func (c *Context) ShouldBindBodyWith(obj interface{}, bb binding.BindingBody) (err error) {
var body []byte
if cb, ok := c.Get(BodyBytesKey); ok {
if cbb, ok := cb.([]byte); ok {
body = cbb
}
}
if body == nil {
body, err = ioutil.ReadAll(c.Request.Body)
if err != nil {
return err
}
c.Set(BodyBytesKey, body)
}
return bb.BindBody(body, obj)
}
// ClientIP implements a best effort algorithm to return the real client IP.
// It called c.RemoteIP() under the hood, to check if the remote IP is a trusted proxy or not.
// If it's it will then try to parse the headers defined in Engine.RemoteIPHeaders (defaulting to [X-Forwarded-For, X-Real-Ip]).
// If the headers are nots syntactically valid OR the remote IP does not correspong to a trusted proxy,
// the remote IP (coming form Request.RemoteAddr) is returned.
func (c *Context) ClientIP() string {
if c.engine.AppEngine {
if addr := c.requestHeader("X-Appengine-Remote-Addr"); addr != "" {
return addr
}
}
remoteIP, trusted := c.RemoteIP()
if remoteIP == nil {
return ""
}
if trusted && c.engine.ForwardedByClientIP && c.engine.RemoteIPHeaders != nil {
for _, headerName := range c.engine.RemoteIPHeaders {
ip, valid := validateHeader(c.requestHeader(headerName))
if valid {
return ip
}
}
}
return remoteIP.String()
}
// RemoteIP parses the IP from Request.RemoteAddr, normalizes and returns the IP (without the port).
// It also checks if the remoteIP is a trusted proxy or not.
// In order to perform this validation, it will see if the IP is contained within at least one of the CIDR blocks
// defined in Engine.TrustedProxies
func (c *Context) RemoteIP() (net.IP, bool) {
ip, _, err := net.SplitHostPort(strings.TrimSpace(c.Request.RemoteAddr))
if err != nil {
return nil, false
}
remoteIP := net.ParseIP(ip)
if remoteIP == nil {
return nil, false
}
if c.engine.trustedCIDRs != nil {
for _, cidr := range c.engine.trustedCIDRs {
if cidr.Contains(remoteIP) {
return remoteIP, true
}
}
}
return remoteIP, false
}
func validateHeader(header string) (clientIP string, valid bool) {
if header == "" {
return "", false
}
items := strings.Split(header, ",")
for i, ipStr := range items {
ipStr = strings.TrimSpace(ipStr)
ip := net.ParseIP(ipStr)
if ip == nil {
return "", false
}
// We need to return the first IP in the list, but,
// we should not early return since we need to validate that
// the rest of the header is syntactically valid
if i == 0 {
clientIP = ipStr
valid = true
}
}
return
}
// ContentType returns the Content-Type header of the request.
func (c *Context) ContentType() string {
return filterFlags(c.requestHeader("Content-Type"))
}
// IsWebsocket returns true if the request headers indicate that a websocket
// handshake is being initiated by the client.
func (c *Context) IsWebsocket() bool {
if strings.Contains(strings.ToLower(c.requestHeader("Connection")), "upgrade") &&
strings.EqualFold(c.requestHeader("Upgrade"), "websocket") {
return true
}
return false
}
func (c *Context) requestHeader(key string) string {
return c.Request.Header.Get(key)
}
gin 中像上面的对 cookie 、header、body 的存取和 c.JSON、c.HTML 等决定输出渲染类型统归类为 RESPONSE RENDERING（响应渲染），各类方法的源代码如下：
/************************************/
/******** RESPONSE RENDERING ********/
/************************************/
// bodyAllowedForStatus is a copy of http.bodyAllowedForStatus non-exported function.
func bodyAllowedForStatus(status int) bool {
switch {
case status >= 100 && status <= 199:
return false
case status == http.StatusNoContent:
return false
case status == http.StatusNotModified:
return false
}
return true
}
// Status sets the HTTP response code.
func (c *Context) Status(code int) {
c.Writer.WriteHeader(code)
}
// Header is a intelligent shortcut for c.Writer.Header().Set(key, value).
// It writes a header in the response.
// If value == "", this method removes the header `c.Writer.Header().Del(key)`
func (c *Context) Header(key, value string) {
if value == "" {
c.Writer.Header().Del(key)
return
}
c.Writer.Header().Set(key, value)
}
// GetHeader returns value from request headers.
func (c *Context) GetHeader(key string) string {
return c.requestHeader(key)
}
// GetRawData return stream data.
func (c *Context) GetRawData() ([]byte, error) {
return ioutil.ReadAll(c.Request.Body)
}
// SetSameSite with cookie
func (c *Context) SetSameSite(samesite http.SameSite) {
c.sameSite = samesite
}
// SetCookie adds a Set-Cookie header to the ResponseWriter's headers.
// The provided cookie must have a valid Name. Invalid cookies may be
// silently dropped.
func (c *Context) SetCookie(name, value string, maxAge int, path, domain string, secure, httpOnly bool) {
if path == "" {
path = "/"
}
http.SetCookie(c.Writer, &http.Cookie{
Name: name,
Value: url.QueryEscape(value),
MaxAge: maxAge,
Path: path,
Domain: domain,
SameSite: c.sameSite,
Secure: secure,
HttpOnly: httpOnly,
})
}
// Cookie returns the named cookie provided in the request or
// ErrNoCookie if not found. And return the named cookie is unescaped.
// If multiple cookies match the given name, only one cookie will
// be returned.
func (c *Context) Cookie(name string) (string, error) {
cookie, err := c.Request.Cookie(name)
if err != nil {
return "", err
}
val, _ := url.QueryUnescape(cookie.Value)
return val, nil
}
// Render writes the response headers and calls render.Render to render data.
func (c *Context) Render(code int, r render.Render) {
c.Status(code)
if !bodyAllowedForStatus(code) {
r.WriteContentType(c.Writer)
c.Writer.WriteHeaderNow()
return
}
if err := r.Render(c.Writer); err != nil {
panic(err)
}
}
// HTML renders the HTTP template specified by its file name.
// It also updates the HTTP code and sets the Content-Type as "text/html".
// See http://golang.org/doc/articles/wiki/
func (c *Context) HTML(code int, name string, obj interface{}) {
instance := c.engine.HTMLRender.Instance(name, obj)
c.Render(code, instance)
}
// IndentedJSON serializes the given struct as pretty JSON (indented + endlines) into the response body.
// It also sets the Content-Type as "application/json".
// WARNING: we recommend to use this only for development purposes since printing pretty JSON is
// more CPU and bandwidth consuming. Use Context.JSON() instead.
func (c *Context) IndentedJSON(code int, obj interface{}) {
c.Render(code, render.IndentedJSON{Data: obj})
}
// SecureJSON serializes the given struct as Secure JSON into the response body.
// Default prepends "while(1)," to response body if the given struct is array values.
// It also sets the Content-Type as "application/json".
func (c *Context) SecureJSON(code int, obj interface{}) {
c.Render(code, render.SecureJSON{Prefix: c.engine.secureJSONPrefix, Data: obj})
}
// JSONP serializes the given struct as JSON into the response body.
// It adds padding to response body to request data from a server residing in a different domain than the client.
// It also sets the Content-Type as "application/javascript".
func (c *Context) JSONP(code int, obj interface{}) {
callback := c.DefaultQuery("callback", "")
if callback == "" {
c.Render(code, render.JSON{Data: obj})
return
}
c.Render(code, render.JsonpJSON{Callback: callback, Data: obj})
}
// JSON serializes the given struct as JSON into the response body.
// It also sets the Content-Type as "application/json".
func (c *Context) JSON(code int, obj interface{}) {
c.Render(code, render.JSON{Data: obj})
}
// AsciiJSON serializes the given struct as JSON into the response body with unicode to ASCII string.
// It also sets the Content-Type as "application/json".
func (c *Context) AsciiJSON(code int, obj interface{}) {
c.Render(code, render.AsciiJSON{Data: obj})
}
// PureJSON serializes the given struct as JSON into the response body.
// PureJSON, unlike JSON, does not replace special html characters with their unicode entities.
func (c *Context) PureJSON(code int, obj interface{}) {
c.Render(code, render.PureJSON{Data: obj})
}
// XML serializes the given struct as XML into the response body.
// It also sets the Content-Type as "application/xml".
func (c *Context) XML(code int, obj interface{}) {
c.Render(code, render.XML{Data: obj})
}
// YAML serializes the given struct as YAML into the response body.
func (c *Context) YAML(code int, obj interface{}) {
c.Render(code, render.YAML{Data: obj})
}
// ProtoBuf serializes the given struct as ProtoBuf into the response body.
func (c *Context) ProtoBuf(code int, obj interface{}) {
c.Render(code, render.ProtoBuf{Data: obj})
}
// String writes the given string into the response body.
func (c *Context) String(code int, format string, values ...interface{}) {
c.Render(code, render.String{Format: format, Data: values})
}
// Redirect returns a HTTP redirect to the specific location.
func (c *Context) Redirect(code int, location string) {
c.Render(-1, render.Redirect{
Code: code,
Location: location,
Request: c.Request,
})
}
// Data writes some data into the body stream and updates the HTTP code.
func (c *Context) Data(code int, contentType string, data []byte) {
c.Render(code, render.Data{
ContentType: contentType,
Data: data,
})
}
// DataFromReader writes the specified reader into the body stream and updates the HTTP code.
func (c *Context) DataFromReader(code int, contentLength int64, contentType string, reader io.Reader, extraHeaders map[string]string) {
c.Render(code, render.Reader{
Headers: extraHeaders,
ContentType: contentType,
ContentLength: contentLength,
Reader: reader,
})
}
// File writes the specified file into the body stream in an efficient way.
func (c *Context) File(filepath string) {
http.ServeFile(c.Writer, c.Request, filepath)
}
// FileFromFS writes the specified file from http.FileSystem into the body stream in an efficient way.
func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
defer func(old string) {
c.Request.URL.Path = old
}(c.Request.URL.Path)
c.Request.URL.Path = filepath
http.FileServer(fs).ServeHTTP(c.Writer, c.Request)
}
// FileAttachment writes the specified file into the body stream in an efficient way
// On the client side, the file will typically be downloaded with the given filename
func (c *Context) FileAttachment(filepath, filename string) {
c.Writer.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename="%s"", filename))
http.ServeFile(c.Writer, c.Request, filepath)
}
// SSEvent writes a Server-Sent Event into the body stream.
func (c *Context) SSEvent(name string, message interface{}) {
c.Render(-1, sse.Event{
Event: name,
Data: message,
})
}
// Stream sends a streaming response and returns a boolean
// indicates "Is client disconnected in middle of stream"
func (c *Context) Stream(step func(w io.Writer) bool) bool {
w := c.Writer
clientGone := w.CloseNotify()
for {
select {
case <-clientGone:
return true
default:
keepOpen := step(w)
w.Flush()
if !keepOpen {
return false
}
}
}
}
Http Request
在 golang 中使用 http 包可以很方便的实现一个简单的服务器，如下：
package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.HandleFunc("/user", func(writer http.ResponseWriter, request *http.Request) {
//writer.Write()
_, err :=writer.Write([]byte("hello world"))
if err!= nil {
fmt.Println(err)
}
})
err := http.ListenAndServe(":8000",nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
和 gin 一样，路由的 handler 中都涉及到 http.ResponseWriter 和 http.Request 这两个对象，在 gin 中 http.ResponseWriter 被包裹在了一个 *ResponseWriter 对象中，http.Request 则是直接挂在 context 上的：
中间件
gin 的中间件可以类比 koa 的中间件，是一种洋葱模型，这个模型的中心是最终处理请求的 handler，称之为 main handler，其他为称为 middleware handler，每一个 middleware handle 可以分为两部分，随着 request 的流动，左边是入，右边为出，而分割点就是 next，本质就是通过这个next来执行函数链 ，各个中间件符合先进后出原则：
如下自定义两个全局使用的中间件，可以反映出这个模型：
package main
import (
"fmt"
"github.com/gin-gonic/gin"
"net/http"
)
func m1() gin.HandlerFunc{
return func(c *gin.Context) {
fmt.Println("m1 start")
c.Next()
fmt.Println("m1 end")
}
}
func m2() gin.HandlerFunc {
return func(c *gin.Context) {
fmt.Println("m2 start")
c.Next()
fmt.Println("m2 end")
}
}
func main() {
r := gin.New()
r.Use(m1())
r.Use(m2())
r.GET("/user", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"code": 200,
"data": "user",
})
})
r.Run(":8000")
}
当请求打进来的时候，输出将是 m1 start、m2 start、m2 end、m1 start：
在上文最常用的 gin.Default 中默认使用了 Logger 和 Recovery 作为全局中间件，分别作为日志和 panic 处理，这种直接使用 engine 的 Use 方法来挂载中间件的方法，会使得中间件在全局起作用
和 koa 类似，我们可以把中间件挂载在路由和路由组上，这样这些中间件就只会在匹配的路由中生效，如下，m1 只会在 user 这个路由组下生效，m2 则只会在 /article 这个路由下生效：
package main
import (
"fmt"
"github.com/gin-gonic/gin"
"net/http"
)
func m1() gin.HandlerFunc{
return func(c *gin.Context) {
fmt.Println("m1 start")
c.Next()
fmt.Println("m1 end")
}
}
func m2() gin.HandlerFunc {
return func(c *gin.Context) {
fmt.Println("m2 start")
c.Next()
fmt.Println("m2 end")
}
}
func main() {
r := gin.New()
userRouter := r.Group("/user", m1())
userRouter.GET("/info", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"code": 200,
"data": "info",
})
})
r.GET("/article", m2(), func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"code": 200,
"data": "article",
})
})
r.Run(":8000")
}
在实际开发中经常需要自定义中间件，一个中间件本质上就是一个 handler 函数即是一个以 *gin.Context 为参数的函数，在实际开发中中间件可以是一个返回 handler 的函数，这样使用的时候调用这个函数即可，如果本身就是一个 handler，则不需要调用，直接作为参数即可：
package main
import (
"fmt"
"github.com/gin-gonic/gin"
"net/http"
)
func middle1() gin.HandlerFunc{
return func(c *gin.Context) {
fmt.Println("middleware 1")
c.Next()
}
}
func middle2(c *gin.Context) {
fmt.Println("middleware 2")
c.Next()
}
func main() {
r := gin.Default()
r.Use(middle1())
r.Use(middle2)
r.GET("/user", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"data": "user",
})
})
r.Run(":8000")
}
中间件中除了 Next 外还可以使用 Abort、AbortWithStatus、AbortWithStatusJSON、AbortWithError 方法拦截请求，这种常常可以用于鉴权、鉴参数等前置流程，如下，当请求的 header 没有 token 时会拦截请求，直接返回没权限：
package main
import (
"github.com/gin-gonic/gin"
"net/http"
)
func auth() gin.HandlerFunc{
return func(c *gin.Context) {
token := c.GetHeader("token")
if token == "" {
c.AbortWithStatusJSON(401, gin.H{
"message": "没有权限",
})
}
c.Next()
}
}
func main() {
r := gin.Default()
r.Use(auth())
r.GET("/user", func(c *gin.Context) {
c.JSON(http.StatusOK, gin.H{
"data": "user",
})
})
r.Run(":8000")
}
在 gin 的 官方文档下，可以看到官方维护和外部维护的中间件列表：github.com/gin-gonic/c…
脚手架工程
可参考的开源代码仓库
参考
今天的文章Go web 框架 gin 的使用分享到此就结束了，感谢您的阅读。
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