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Gin Web Framework

使用自定义结构体标签绑定表单数据

默认情况下，Gin 使用 form 结构体标签来绑定表单数据。当你需要绑定一个使用不同标签的结构体时——例如一个你无法修改的外部类型——你可以创建一个自定义绑定来读取你自己的标签。

当集成第三方库时，如果其结构体使用 url、query 或其他自定义名称而非 form 标签，这将非常有用。

package main


import (
  "net/http"


  "github.com/gin-gonic/gin"
  "github.com/gin-gonic/gin/binding"
)


const (
  customerTag   = "url"
  defaultMemory = 32 << 20
)


type customerBinding struct{}


func (customerBinding) Name() string {
  return "form"
}


func (customerBinding) Bind(req *http.Request, obj any) error {
  if err := req.ParseForm(); err != nil {
    return err
  }
  if err := req.ParseMultipartForm(defaultMemory); err != nil {
    if err != http.ErrNotMultipart {
      return err
    }
  }
  if err := binding.MapFormWithTag(obj, req.Form, customerTag); err != nil {
    return err
  }
  return validate(obj)
}


func validate(obj any) error {
  if binding.Validator == nil {
    return nil
  }
  return binding.Validator.ValidateStruct(obj)
}


// FormA is an external type that we can't modify its tag
type FormA struct {
  FieldA string `url:"field_a"`
}


func main() {
  router := gin.Default()


  router.GET("/list", func(c *gin.Context) {
    var urlBinding = customerBinding{}
    var opt FormA
    if err := c.MustBindWith(&opt, urlBinding); err != nil {
      return
    }
    c.JSON(http.StatusOK, gin.H{"field_a": opt.FieldA})
  })


  router.Run(":8080")
}

测试

Terminal window
# The custom binding reads from the "url" struct tag instead of "form"
curl "http://localhost:8080/list?field_a=hello"
# Output: {"field_a":"hello"}


# Missing parameter -- empty string
curl "http://localhost:8080/list"
# Output: {"field_a":""}

另请参阅