Golang : Adding XML attributes to xml data or use attribute to differentiate a common tag name



Tags : golang xml attributes attr marshalindent

Problem :

There are times when we want to produce XML files that are easier to read by human eyes and you happen to have a Golang program that produce XML data that look like this :

  <person>
 <id>13</id>
 <name>
 <first>John</first>
 <last>Doe</last>
 </name>
 <age>42</age>
 <Married>false</Married>
 <City>Hanga Roa</City>
 <State>Easter Island</State>
 <!-- Need more details. -->
  </person>

To make it more readable, you want to make the field ID as a XML attribute of the Person instead of separate tag. Or you want to make the XML data to become more readable such as :

 <HostProperties>
 <tag name="HOST_END">Thu Feb 20 12:38:24 2014</tag>
 <tag name="patch-summary-total-cves">4</tag>
 <tag name="host-fqdn">foobar.com</tag>
 <tag name="HOST_START">Thu Feb 20 12:30:14 2014</tag>
 </HostProperties>

with the XML attribute name to differentiate each tags

How to do that ?

Solution :

Add the attr tag into Person structure. For example :

 type Person struct {
  XMLName xml.Name `xml:"person"`
  Id int `xml:"id,attr"` //<--- add attr and see what will happen
  FirstName string `xml:"name>first"`
  LastName  string `xml:"name>last"`
  Age int `xml:"age"`
  Height float32  `xml:"height,omitempty"`
  Married bool
  Address
  Comment string `xml:",comment"`
 }

the output will become :

  <person id="13">
 <name>
 <first>John</first>
 <last>Doe</last>
 </name>
 <age>42</age>
 <Married>false</Married>
 <City>Hanga Roa</City>
 <State>Easter Island</State>
 <!-- Need more details. -->
  </person>

The complete code :

 package main

 import (
  "encoding/xml"
  "fmt"
 )

 type Address struct {
  City, State string
 }
 type Person struct {
  XMLName xml.Name `xml:"person"`
  Id int `xml:"id,attr"` //<--- remove attr and see what will happen
  FirstName string `xml:"name>first"`
  LastName  string `xml:"name>last"`
  Age int `xml:"age"`
  Height float32  `xml:"height,omitempty"`
  Married bool
  Address
  Comment string `xml:",comment"`
 }

 func main() {
  v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
  v.Comment = " Need more details. "
  v.Address = Address{"Hanga Roa", "Easter Island"}

  output, err := xml.MarshalIndent(v, " ", " ")
  if err != nil {
 fmt.Printf("error: %v\n", err)
  }

  fmt.Println(string(output))
 }

Play at : http://play.golang.org/p/mioNj3kht-

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Tags : golang xml attributes attr marshalindent

By Adam Ng

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