json: 字符串结构标签的使用无效

Question

我正在尝试编写简单的 POST 无服务器 Go AWS lambda 函数。

package main

import (
    "fmt"
)

import (
    "encoding/json"
    "github.com/aws/aws-lambda-go/events"
    "github.com/aws/aws-lambda-go/lambda"
)

// RequestBodyType is our self-made struct to process JSON request from Client
type RequestBodyType struct {
    Event       string `string:"event,string,omitempty"`
    EventParams EventParamsType
}

// ResponseBodyType is our self-made struct to build response for Client
type ResponseBodyType struct {
    Event       string `string:"event,string,omitempty"`
    EventParams EventParamsType
}

// Probably problematic struct?
type EventParamsType struct {
    Name string `json:"name,string,omitempty"`
    Age  int64  `json:"age,omitempty"`
}

// Handler function Using AWS Lambda Proxy Request
func Handler(request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {

    // RequestBody will be used to take the json response from client and build it
    requestBody := RequestBodyType{
        Event: "",
        EventParams: EventParamsType{
            Name: "",
            Age:  0,
        },
    }

    // Unmarshal the json, return 404 if error
    err := json.Unmarshal([]byte(request.Body), &requestBody)
    if err != nil {
        return events.APIGatewayProxyResponse{Body: err.Error(), StatusCode: 404}, nil
    }

    // We will build the BodyResponse and send it back in json form
    responseBody := &ResponseBodyType{
        Event:       requestBody.Event,
        EventParams: EventParamsType{
            Name: requestBody.EventParams.Name,
            Age: requestBody.EventParams.Age,   
        },
    }

    fmt.Println("RESPONSE BODY")
    fmt.Println(responseBody)

    // Marshal the response into json bytes, if error return 404
    response, err := json.Marshal(&responseBody)
    if err != nil {
        return events.APIGatewayProxyResponse{Body: err.Error(), StatusCode: 404}, nil
    }

    //Returning response with AWS Lambda Proxy Response
    return events.APIGatewayProxyResponse{Body: string(response), StatusCode: 200}, nil
}

func main() {
    lambda.Start(Handler)
}

如果我使用单个 JSON 对象键发出 curl 请求，一切正常，例如：

curl -X POST https://my.url/dev/event  -d '{"event": "test"}'

然后我收到回复

{"Event":"test","EventParams":{}

但是如果我使用嵌套的 json 对象发出请求，例如：

curl -X POST https://my.url/dev/event  -d '{"event": "test","eventParams": {"name": "peter","age": 13}}'

然后我得到回应

json: invalid use of ,string struct tag, trying to unmarshal "peter" into string

我相信我可能设计了 EventParamsType 错误的方式？还是我构建 ResponseBodyType 的方式有误？

Answer 1

如错误所述，您对 ,string 的使用对于您的 JSON 输入无效。删除它：

    Name string `json:"name,omitempty"`

,string can 在 JSON 标签中有效，它表示该数字应作为字符串文字进行封送处理。对于已经是字符串的值，这意味着它需要一个 JSON 引号字符串（您的输入显然不是）。

这个解释in the docs:

The "string" option signals that a field is stored as JSON inside a JSON-encoded string. It applies only to fields of string, floating point, integer, or boolean types. This extra level of encoding is sometimes used when communicating with JavaScript programs:
Int64String int64 `json:",string"`

有关详细信息，请参阅 in the playground。

此外，正如@Adrian 指出的那样，string: 是一个无意义的标签（无论如何，为了 JSON（未）编组的目的）。您可能需要 json: 而不是 string: （尽管某些库可能使用名为 string:...

的标签

json: 字符串结构标签的使用无效

json: invalid use of string struct tag

struct

go

aws-lambda

aws-lambda-go