How to let golang distinguish between XML elements with namespace and without namespace?

php editor Zimo will share with you how to let golang distinguish XML elements with namespaces and without namespaces. When dealing with XML data, namespace is an important concept that can help us better organize and distinguish different XML elements. This article will introduce how to use golang's xml package to parse and process XML elements with and without namespaces, and provide some sample codes for practical applications. Whether you are a beginner or an experienced developer, you will gain valuable knowledge and tips from this article. Let’s explore this fun and practical topic together!

Question content

Suppose I have the following xml data:

<image> 
  <url> http://sampleurl.com
  </url>
</image>

<itunes:image url="http://sampleitunesurl.com" />  //xmldata

I use this structure to decode it:

type response struct {
   xmlname   xml.name   `xml:"resp"`
   image []struct {
        url string   `xml:"url"`
  } `xml:"image"`
  itunesimage  struct {
       url string `xml:"url,attr"`
  }  `xml:"http://www.itunes.com/dtds/podcast-1.0.dtd image"`

}

I have this code:

var resp Response 
err := xml.Unmarshal([]byte(xmlData), &resp)
if err != nil {
    fmt.Printf("Error decoding XML: %s\n", err)
    return
}
for _, img := range resp.Image{
    if img.URL != "" {
        //<image>, not <itunes:image>
    }
}

Processing decoding

The problem I'm having is that it looks like image []struct thinks <image></image> and are both <image></image> elements because they all have "images". To filter out <image>, the approach I used was to have everyone in the <code>image []struct check if their url was an empty string ( Because for <image> its <code>url is an attribute).

Another approach is to write my own unmarshal function to differentiate between xml elements with and without itunes namespace. Basically I want image []struct to save only the element <image></image>

I wonder if go has some built-in functionality to differentiate? Or do I have to write code to filter out <image></image>?

Solution

Please note that field order is important. itunesimage has a more specific tag, so it should come before image.

package main

import (
    "encoding/xml"
    "fmt"
)

func main() {
    type response struct {
        xmlname     xml.name `xml:"resp"`
        itunesimage struct {
            url string `xml:"url,attr"`
        } `xml:"http://www.itunes.com/dtds/podcast-1.0.dtd image"`
        image []struct {
            url string `xml:"url"`
        } `xml:"image"`
    }

    xmldata := `
<resp xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
  <image>
    <url>http://sampleurl.com</url>
  </image>
  <itunes:image url="http://sampleitunesurl.com/" />
</resp>
`

    var resp response
    err := xml.unmarshal([]byte(xmldata), &resp)
    if err != nil {
        fmt.printf("error decoding xml: %s\n", err)
        return
    }
    fmt.printf("itunesimage: %v\n", resp.itunesimage)
    fmt.printf("images: %v\n", resp.image)
}

If you only need the <image></image> in the image/url tag, you can define the response structure like this:

type response struct {
    xmlname xml.name `xml:"resp"`
    image   []string `xml:"image>url"`
}

Regarding the general question in the title (how to make golang differentiate between xml elements with and without namespaces?), you can capture the element name using a field called xmlname, and check that field Member of space. See demo below:

package main

import (
    "encoding/xml"
    "fmt"
)

func main() {
    type response struct {
        xmlname xml.name `xml:"resp"`
        image   []struct {
            xmlname xml.name
            url     string `xml:"url"`
        } `xml:"image"`
    }

    xmldata := `
<resp xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
  <image>
    <url>http://sampleurl.com</url>
  </image>
  <itunes:image>
    <url>http://sampleitunesurl.com/</url>
  </itunes:image>
</resp>
`

    var resp response
    err := xml.unmarshal([]byte(xmldata), &resp)
    if err != nil {
        fmt.printf("error decoding xml: %s\n", err)
        return
    }
    for _, img := range resp.image {
        fmt.printf("namespace: %q, url: %s\n", img.xmlname.space, img.url)
    }
}

The output of the above demonstration is:

namespace: "", url: http://sampleUrl.com
namespace: "http://www.itunes.com/dtds/podcast-1.0.dtd", url: http://sampleItunesUrl.com/

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