在绑定之前显式处理 gzipped json

Question

我想写一个 api 将用 POST 发送 gzipped json 数据。虽然下面可以处理正文中的简单 json，但如果 json 被压缩，则不会处理。

我们在使用c.ShouldBindJSON之前是否需要明确处理解压缩？

如何重现

package main

import (
    "github.com/gin-gonic/gin"
    "log"
    "net/http"
)

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

    r.POST("/postgzip", func(c *gin.Context) {
        
        type PostData struct {
            Data string `binding:"required" json:"data"`
        }
        
        var postdata PostData
        if err := c.ShouldBindJSON(&postdata); err != nil {
            log.Println("Error parsing request body", "error", err)
            c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": err.Error()})
            return
        }
        log.Printf("%s", postdata)
        if !c.IsAborted() {
            c.String(200, postdata.Data)
        }
    })
    r.Run()
}

❯ echo '{"data" : "hello"}' | curl -X POST -H "Content-Type: application/json" -d @- localhost:8080/postgzip
hello

预期

$ echo '{"data" : "hello"}' | gzip | curl -v -i -X POST -H "Content-Type: application/json" -H "Content-Encoding: gzip" --data-binary @- localhost:8080/postgzip
hello

实际结果

$ echo '{"data" : "hello"}' | gzip | curl -v -i -X POST -H "Content-Type: application/json" -H "Content-Encoding: gzip" --data-binary @- localhost:8080/postgzip
{"error":"invalid character '\x1f' looking for beginning of value"}

环境

go 版本：go version go1.17.2 darwin/amd64
gin 版本（或提交参考）：v1.7.4
操作系统：MacOS Monterey

Answer 1

Do we need to explicitly handle the decompression before using c.ShouldBindJSON ?

当然可以。 Gin ShouldBindJSON 不知道您的有效负载如何编码或不编码。 It expects JSON input，顾名思义。

如果您希望编写可重用的代码，您可以实现 Binding 接口。

一个非常简单的例子：

type GzipJSONBinding struct {
}

func (b *GzipJSONBinding) Name() string {
    return "gzipjson"
}

func (b *GzipJSONBinding) Bind(req *http.Request, dst interface{}) error {
    r, err := gzip.NewReader(req.Body)
    if err != nil {
        return err
    }
    raw, err := io.ReadAll(r)
    if err != nil {
        return err
    }
    return json.Unmarshal(raw, dst)
}

然后可用于 c.ShouldBindWith，这允许使用任意绑定引擎：

err := c.ShouldBindWith(&postData, &GzipJSONBinding{})

Answer 2

打开 `Content-Encoding`

的完整示例

curl 尝试使用它

$ echo '{"data" : "hello"}' | gzip | curl -X POST -H "Content-Type: application/json" -H "Content-Encoding: gzip" --data-binary @- localhost:8080/json
hello

$ curl -X POST -H "Content-Type: application/json" --data-raw '{"data" : "hello"}' localhost:8080/json
hello

package main

import (
    "bytes"
    "compress/gzip"
    "encoding/json"
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
    "io"
    "log"
    "net/http"
)

type PostData struct {
    Data string `binding:"required" json:"data"`
}

func main() {
    r := gin.Default()
    r.POST("/json", func(c *gin.Context) {

        var postdata PostData

        contentEncodingHeader := c.GetHeader("Content-Encoding")
        switch contentEncodingHeader {
        case "gzip":
            if err := c.ShouldBindBodyWith(&postdata, gzipJSONBinding{}); err != nil {
                log.Println("Error parsing GZIP JSON request body", "error", err)
                c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": err.Error()})
                return
            }
        case "":
            if err := c.ShouldBindJSON(&postdata); err != nil {
                log.Println("Error parsing JSON request body", "error", err)
                c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": err.Error()})
                return
            }
        default:
            log.Println("unsupported Content-Encoding")
            c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"error": "unsupported Content-Encoding"})
            return

        }

        log.Printf("%s", postdata)
        if !c.IsAborted() {
            c.String(200, postdata.Data)
        }
    })
    r.Run()
}

type gzipJSONBinding struct{}

func (gzipJSONBinding) Name() string {
    return "gzipjson"
}

func (gzipJSONBinding) Bind(req *http.Request, obj interface{}) error {
    if req == nil || req.Body == nil {
        return fmt.Errorf("invalid request")
    }
    r, err := gzip.NewReader(req.Body)
    if err != nil {
        return err
    }
    raw, err := io.ReadAll(r)
    if err != nil {
        return err
    }
    return json.Unmarshal(raw, obj)
}

func (gzipJSONBinding) BindBody(body []byte, obj interface{}) error {
    r, err := gzip.NewReader(bytes.NewReader(body))
    if err != nil {
        return err
    }
    return decodeJSON(r, obj)
}

func decodeJSON(r io.Reader, obj interface{}) error {
    decoder := json.NewDecoder(r)

    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)
}

在绑定之前显式处理 gzipped json

Explicitly handle gzipped json before binding

json

go

gzip

go-gin

如何重现

预期

实际结果

环境

打开 `Content-Encoding`

在绑定之前显式处理 gzipped json

Explicitly handle gzipped json before binding

json

go

gzip

go-gin

如何重现

预期

实际结果

环境

打开 Content-Encoding

打开 `Content-Encoding`