Gin 框架绑定 JSON 参数使用 jsoniter
Gin 框架中，处理 JSON 格式的参数绑定时，默认采用的标准包 encoding/json，然而标准包不能满足我们的一些要求，比如兼容字符串整型、PHP 空数组、时间格式等。
Gin 框架中，处理 JSON 格式的参数绑定时，默认采用的标准包 encoding/json，然而标准包不能满足我们的一些要求，比如兼容字符串整型、PHP 空数组、时间格式等。
最简单的方式
开发 API 时，需要用到 ShouldBindJSON 绑定传入的参数到结构体：
// github.com/gin-gonic/gin@v1.6.3/context.go:643// ShouldBindJSON is a shortcut for c.ShouldBindWith(obj, binding.JSON).func (c *Context) ShouldBindJSON(obj interface{}) error {return c.ShouldBindWith(obj, binding.JSON)}
Gin 默认采用 encoding/json 包：
// github.com/gin-gonic/gin@v1.6.3/internal/json/json.go// +build !jsoniterpackage jsonimport "encoding/json"var (// Marshal is exported by gin/json package.Marshal = json.Marshal// Unmarshal is exported by gin/json package.Unmarshal = json.Unmarshal// MarshalIndent is exported by gin/json package.MarshalIndent = json.MarshalIndent// NewDecoder is exported by gin/json package.NewDecoder = json.NewDecoder// NewEncoder is exported by gin/json package.NewEncoder = json.NewEncoder)
同时我们看到还支持了 jsoniter
// github.com/gin-gonic/gin@v1.6.3/internal/json/jsoniter.go// +build jsoniterpackage jsonimport "github.com/json-iterator/go"var (json = jsoniter.ConfigCompatibleWithStandardLibrary// Marshal is exported by gin/json package.Marshal = json.Marshal// Unmarshal is exported by gin/json package.Unmarshal = json.Unmarshal// MarshalIndent is exported by gin/json package.MarshalIndent = json.MarshalIndent// NewDecoder is exported by gin/json package.NewDecoder = json.NewDecoder// NewEncoder is exported by gin/json package.NewEncoder = json.NewEncoder)
那我们怎么才能使用到 jsoniter 呢？源码中已经明确了编译 tag：
所以，我们只需在编译时带上这个 tag 就可以了，例如：
go build -tags=jsoniter main.go// 或者go run -tags=jsoniter main.go
自定义的方式
Gin 框架支持的 jsoniter 是默认配置 jsoniter.ConfigCompatibleWithStandardLibrary。当我们需要其他配置或添加一些自定义扩展（比如时间处理）时，就难受了。于是我们就要自己动手了~
翻开源码，我们能看到 binding.JSON 其实使用的是 jsonBinding{} 这个结构体：
// github.com/gin-gonic/gin@v1.6.3/binding/binding.go:73// These implement the Binding interface and can be used to bind the data// present in the request to struct instances.var (JSON = jsonBinding{}// 其他省略了...)
翻开 jsonBinding 源码看看：
// github.com/gin-gonic/gin@v1.6.3/binding/json.gotype jsonBinding struct{}func (jsonBinding) Name() string {return "json"}func (jsonBinding) Bind(req *http.Request, obj interface{}) error {if req == nil || req.Body == nil {return fmt.Errorf("invalid request")}return decodeJSON(req.Body, obj)}func (jsonBinding) BindBody(body []byte, obj interface{}) error {return decodeJSON(bytes.NewReader(body), obj)}
发现实现了 BindingBody 这个接口：
// github.com/gin-gonic/gin@v1.6.3/binding/binding.go:36// Binding describes the interface which needs to be implemented for binding the// data present in the request such as JSON request body, query parameters or// the form POST.type Binding interface {Name() stringBind(*http.Request, interface{}) error}// BindingBody adds BindBody method to Binding. BindBody is similar with Bind,// but it reads the body from supplied bytes instead of req.Body.type BindingBody interface {BindingBindBody([]byte, interface{}) error}
那接下来就简单了，我们只要实现了这个接口即可，例如：
package customimport ("bytes""fmt""io""net/http"jsoniter "github.com/json-iterator/go""github.com/gin-gonic/gin/binding")// BindingJSON 替换Gin默认的binding，支持更丰富JSON功能var BindingJSON = jsonBinding{}// 可以自定义jsoniter配置或者添加插件var json = jsoniter.ConfigCompatibleWithStandardLibrarytype jsonBinding struct{}func (jsonBinding) Name() string {return "json"}func (jsonBinding) Bind(req *http.Request, obj interface{}) error {if req == nil || req.Body == nil {return fmt.Errorf("invalid request")}return decodeJSON(req.Body, obj)}func (jsonBinding) BindBody(body []byte, obj interface{}) error {return decodeJSON(bytes.NewReader(body), obj)}func decodeJSON(r io.Reader, obj interface{}) error {decoder := json.NewDecoder(r)if binding.EnableDecoderUseNumber {decoder.UseNumber()}if binding.EnableDecoderDisallowUnknownFields {decoder.DisallowUnknownFields()}if err := decoder.Decode(obj); err != nil {return err}return validate(obj)}func validate(obj interface{}) error {if binding.Validator == nil {return nil}return binding.Validator.ValidateStruct(obj)}
自定义 jsonBinding 已经写好了，可使用有 2 种方式：
// binding.JSON 替换成自定义的ctx.ShouldBindWith(¶ms, binding.JSON)ctx.ShouldBindBodyWith(¶ms, binding.JSON)
上述自定义的方式，还可以用于其他包，不仅限于 iterator。从这个方面体现出了 Gin 框架良好的接口设计👍。
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