Golang beego输出到csv文件将数据转储到浏览器，但不会转储到文件 [英] Golang beego output to csv file dumps the data to browser but not dump to file

问题描述

我尝试在golang beego框架中输出一些数据到csv文件，这里是我的代码

  records：= make [] [] string，len（devicesData））
 
 for k，v：= range devicesData {
 records [k] = [] string {v.Fields.Country，v.Fields .Imei [0]，v.Fields.Number [0]} 
} 
 
编写者：= csv.NewWriter（this.Controller.Ctx.ResponseWriter）
 for _，记录：=范围记录{
 err：= writer.Write（record）
 if err！= nil {
 fmt.Println（Error：，err）
 return 
 
 
 
 this.Ctx.Output.Header（Content-Type，application / csv）
 this.Ctx.Output.Header（ Content-Disposition，attachment; filename = MyVerySpecial.csv）
 
 writer.Flush（）
  

但是，它只显示浏览器中的记录数据，无法下载文件。我在这个下载文件控制器之前有一些登录控制器和过滤功能，我不知道它是否受到影响。我的代码有什么问题？谢谢 您应该始终设置响应标头第一，并且只有在开始将任何数据写入输出。我知道你在设置标题字段后调用了 writer.Flush（），但这并不能保证数据在之前不会被刷新或发送 - 这意味着默认标题为发送。在此之后，不能发送或更改其他头文件。

CSV的正确MIME类型是 text / csv 不是 application / csv （ rfc4180 ）。

此外，标题更像浏览器的提案。这是你建议的一个反应是要保存的文件，但是从服务器端你不能强制浏览器真正保存对文件的响应并且不显示它。

请参阅 rfc1806 ， rfc2183 和 rfc6266 获取有关Content-Disposition标题字段的更多详细信息。基本上，它传达了演示信息。

Content-Disposition响应头字段用于传达
有关如何处理响应负载和
也可以用于附加额外的元数据，例如在本地保存响应负载时使用的文件名
。

I tried to ouput some data to csv file in golang beego framework, here is my code

records := make([][]string,len(devicesData))

for k,v := range devicesData{
    records[k] = []string{v.Fields.Country,v.Fields.Imei[0],v.Fields.Number[0]}
}

writer := csv.NewWriter(this.Controller.Ctx.ResponseWriter)
for _, record := range records {
    err := writer.Write(record)
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
}

this.Ctx.Output.Header("Content-Type", "application/csv")
this.Ctx.Output.Header("Content-Disposition", "attachment; filename=MyVerySpecial.csv")

    writer.Flush()

However, it only shows the record data in browser, it cannot download the file. I have some loging controller and filter function before this download file controller, I do not whether it is affected. What's wrong with my code? Thanks

解决方案

You should always set response headers first and only after that start writing any data to the output. I know you called writer.Flush() after setting header fields, but that is no guarantee whatsoever that data will not be flushed or sent before that - which will imply default headers being sent. After this no additional headers can be sent or changed.

Also the proper mime type for CSV is text/csv not application/csv (rfc4180).

Also the headers are more like a "proposal" to the browser. That's one thing you suggest the response is a file to be saved, but from the server side you can't force the browser to really save the response to a file and not display it.

See rfc1806, rfc2183 and rfc6266 for more details about the "Content-Disposition" header field. Basically it communicates presentation information.

The Content-Disposition response header field is used to convey additional information about how to process the response payload, and also can be used to attach additional metadata, such as the filename to use when saving the response payload locally.

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