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Gin Web Framework

将请求体绑定到不同的结构体

标准的绑定方法如 c.ShouldBind 会消费 c.Request.Body，它是一个 io.ReadCloser——一旦读取后就无法再次读取。这意味着你不能对同一个请求多次调用 c.ShouldBind 来尝试不同的结构体。

要解决这个问题，请使用 c.ShouldBindBodyWith。它会读取一次请求体并将其存储在上下文中，允许后续的绑定重用缓存的请求体。

package main


import (
  "net/http"


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


type formA struct {
  Foo string `json:"foo" xml:"foo" binding:"required"`
}


type formB struct {
  Bar string `json:"bar" xml:"bar" binding:"required"`
}


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


  router.POST("/bind", func(c *gin.Context) {
    objA := formA{}
    objB := formB{}
    // This reads c.Request.Body and stores the result into the context.
    if errA := c.ShouldBindBodyWith(&objA, binding.JSON); errA == nil {
      c.JSON(http.StatusOK, gin.H{"message": "matched formA", "foo": objA.Foo})
      return
    }
    // At this time, it reuses body stored in the context.
    if errB := c.ShouldBindBodyWith(&objB, binding.JSON); errB == nil {
      c.JSON(http.StatusOK, gin.H{"message": "matched formB", "bar": objB.Bar})
      return
    }


    c.JSON(http.StatusBadRequest, gin.H{"error": "request body did not match any known format"})
  })


  router.Run(":8080")
}

测试

Terminal window
# Body matches formA
curl -X POST http://localhost:8080/bind \
  -H "Content-Type: application/json" \
  -d '{"foo":"hello"}'
# Output: {"foo":"hello","message":"matched formA"}


# Body matches formB
curl -X POST http://localhost:8080/bind \
  -H "Content-Type: application/json" \
  -d '{"bar":"world"}'
# Output: {"bar":"world","message":"matched formB"}

另请参阅