xml namespace prefix issue at go

Asked 4/2, 2018 at 15:16 Answered 14/8 at 12:6

marshalling and unmarshalling are not working properly with xml namespace prefix

go version 1.9.2 See below code:

package main

import (

    "fmt"
    "encoding/xml")

type DeviceId struct {
    XMLName      xml.Name `xml:"DeviceId"`
    Manufacturer string   `xml:"Manufacturer"`
    OUI          string   `xml:"OUI"`
    ProductClass string   `xml:"ProductClass"`
    SerialNumber string   `xml:"SerialNumber"`
}

type CwmpInform struct {
    XMLName xml.Name `xml:"cwmp:Inform"`
    DeviceId     DeviceId      
}


func main() {
    rq := new(CwmpInform)
    data := `<cwmp:Inform>
                <DeviceId>
                <Manufacturer></Manufacturer>
                <OUI>48BF74</OUI>
                <ProductClass>FAP</ProductClass>
                <SerialNumber>1202000042177AP0008</SerialNumber>
                </DeviceId>
              </cwmp:Inform>`

    xml.Unmarshal([]byte (data), rq)
    fmt.Printf("Unmarshelled Content:%v", rq)
    output, err := xml.MarshalIndent(rq,"  ", "  ")
    if err != nil{
    fmt.Printf("error : %v", err)
    }
    fmt.Printf("Marshelled Content: %s\n", string(output))
}

Output of above program with proper marshalled Content and empty Marshelled content :

Unmarshelled Content:&{{ } {{ }    }}
 Marshelled Content: 
  <cwmp:Inform>
    <DeviceId>
      <Manufacturer></Manufacturer>
      <OUI></OUI>
      <ProductClass></ProductClass>
      <SerialNumber></SerialNumber>
    </DeviceId>
  </cwmp:Inform>

but when i change the struct's xml tag from xml:"cwmp:Inform" to xml:"cwmp Inform", then Unmarshelling happens properly, but i get below output for Marshelled content :

<Inform xmlns="cwmp">
    <DeviceId>
      <Manufacturer></Manufacturer>
      <OUI>48BF74</OUI>
      <ProductClass>FAP</ProductClass>
      <SerialNumber>1202000042177AP0008</SerialNumber>
    </DeviceId>
  </Inform>

Instead of getting <cwmp:Inform>, I am getting <Inform xmlns="cwmp">

Is there any work around to correct the marshelled content ? Is it a go language Issue ?

Liddle answered 4/2, 2018 at 15:16 Comment(0)

Is probably the same issue here

https://github.com/golang/go/issues/9519

To fix that you need to use two structs, one for Unmarshalling and second to Marshalling data

type CwmpInformUnmarshal struct {
    XMLName  xml.Name `xml:"Inform"`
    DeviceId DeviceId
}

type CwmpInformMarshall struct {
    XMLName  xml.Name `xml:"cwmp:Inform"`
    DeviceId DeviceId
}

Anaglyph answered 4/2, 2018 at 15:46 Comment(6)

Thank you for your answer, but when CwmpInformUnmarshal will be a part of a parent struct and used to Unmarshal against below xml content : <Body> <cwmp:Inform> <DeviceId> <Manufacturer></Manufacturer> <OUI>48BF74</OUI> <ProductClass>FAP</ProductClass> <SerialNumber>1202000042177AP0008</SerialNumber> </DeviceId> </cwmp:Inform> <Body> give output as empty structs :( – Liddle 4/2, 2018 at 17:40

Yeah it's seems that there is something wrong with tags, but when you add Inform to xml.Name it unmarsall it properly. But still you will need to create another BodyM/BodyU struct for this. – Anaglyph 4/2, 2018 at 19:49

Thanks a ton :) @Anaglyph – Liddle 5/2, 2018 at 4:26

Thanks for the workaround it does seem to work but I also ran into the empty structs problem. Can you please explain what you mean by create another BodyM/BodyU struct @Anaglyph – Pilau 6/11, 2019 at 14:41

hello @hoos, I'm happy that this answer helped you to resolve issue. It was some time ago, but if I remember correctly by this I mean thatm for parent struct to properly handle Unmarshal/Marshal you also need to create seperate structs. – Anaglyph 6/11, 2019 at 15:10

Thanks @Anaglyph for the swift response! You are right I needed entirely separate structures for marshalling and unmarshalling. – Pilau 6/11, 2019 at 15:31

I have put namespace prefixes and used https://github.com/nbio/xml as unmarshaller and built-in xml.Marshaller. It solved for me.

Beltz answered 14/8 at 12:6 Comment(0)

marshalling and unmarshalling are not working properly with xml namespace prefix

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