[Gin-v1.9.0 소스코드 읽기] binding/json.go

// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package binding

import (
	"bytes"
	"errors"
	"io"
	"net/http"

	"github.com/gin-gonic/gin/internal/json"
)

// EnableDecoderUseNumber is used to call the UseNumber method on the JSON
// Decoder instance. UseNumber causes the Decoder to unmarshal a number into an
// interface{} as a Number instead of as a float64.
// EnableDecoderUseNumber用于调用JSON Decoder实例上的UseNumber方法。UseNumber使解码器将一个数字解组到接口｛｝中，使其成为number，而不是float64。
var EnableDecoderUseNumber = false

// EnableDecoderDisallowUnknownFields is used to call the DisallowUnknownFields method
// on the JSON Decoder instance. DisallowUnknownFields causes the Decoder to
// return an error when the destination is a struct and the input contains object
// keys which do not match any non-ignored, exported fields in the destination.
// EnableDecoderDisableUnknownFields用于调用JSON Decoder实例上的DisableUnknown Fields方法。
// 当目标为结构并且输入包含与目标中任何未被忽略的导出字段不匹配的对象键时，DisableUnknownFields会导致解码器返回错误。
var EnableDecoderDisallowUnknownFields = false

type jsonBinding struct{}

func (jsonBinding) Name() string {
	return "json"
}

func (jsonBinding) Bind(req *http.Request, obj any) error {
	if req == nil || req.Body == nil {
		return errors.New("invalid request")
	}
	return decodeJSON(req.Body, obj)
}

func (jsonBinding) BindBody(body []byte, obj any) error {
	return decodeJSON(bytes.NewReader(body), obj)
}

func decodeJSON(r io.Reader, obj any) error {
	//  NewDecoder是通过gin/json包导出的
	decoder := json.NewDecoder(r)
	if EnableDecoderUseNumber {
		// UseNumber使解码器将数字解组为接口｛｝中的数字，而不是float64。
		decoder.UseNumber()
	}
	if EnableDecoderDisallowUnknownFields {
		// 当目标是结构并且输入包含与目标中任何未忽略的导出字段不匹配的对象键时，DisableUnknownFields会导致解码器返回错误。
		decoder.DisallowUnknownFields()
	}
	//  Decode从其输入中读取下一个JSON编码值，并将其存储在v指向的值中。
	if err := decoder.Decode(obj); err != nil {
		return err
	}
	return validate(obj)
}