Golang : Search and extract certain XML data example



Tags : golang xml newdecoder extract-attribute chardata

There are times when you want to just search for certain element in huge XML data set and extract the element name and associated value(chardata) or attribute value.

In this tutorial, we will learn how to extract the "normal" type of XML data. Just by the element name and get the chardata value(text in between the element name). Then, followed by extraction example of XML attribute data.

Here you go!

 package main

 import (
  "encoding/xml"
  "fmt"
  "strings"
 )

 var XMLdata = `<urlset>
 <url>
 <loc>http://www.example.com/xml-element-golang</loc>
 <lastmod>2015-06-14</lastmod>
 <changefreq>daily</changefreq>
 <priority>0.5</priority>
 </url>
 <url>
 <loc>http://www.example.com/extract-element-by-for-loop</loc>
 <lastmod>2015-06-14</lastmod>
 <changefreq>daily</changefreq>
 <priority>0.5</priority>
 </url>
 <urlset>`

 var XMLdata2 = `<ALEXA VER="0.9" URL="socketloop.com/" HOME="0" AID="=" IDN="socketloop.com/">
  <SD>
 <POPULARITY URL="socketloop.com/" TEXT="291466" SOURCE="panel"/>
 <REACH RANK="237320"/>
 <RANK DELTA="+31735"/>
 <COUNTRY CODE="US" NAME="United States" RANK="191742"/>
  </SD>
  </ALEXA>`

 // ignore <loc>, only use chardata because DecodeElement will work on <loc>

 type XMLQuery struct {
  Loc string `xml:",chardata"`
 }

 var l XMLQuery

 func main() {

  // example on handling XML chardata(string)
  decoder := xml.NewDecoder(strings.NewReader(string(XMLdata)))

  for {

 // err is ignore here. IF you are reading from a XML file
 // do not ignore err and also check for io.EOF
 token, _ := decoder.Token()

 if token == nil {
 break
 }

 switch Element := token.(type) {
 case xml.StartElement:
 if Element.Name.Local == "loc" {
 fmt.Println("Element name is : ", Element.Name.Local)

 err := decoder.DecodeElement(&l, &Element)
 if err != nil {
 fmt.Println(err)
 }

 fmt.Println("Element value is : ", l.Loc)
 }
 }
  }

  fmt.Println("------------------------------------")

  // example on handling XML attribute
  decoder = xml.NewDecoder(strings.NewReader(string(XMLdata2)))

  for {

 // err is ignore here. IF you are reading from a XML file
 // do not ignore err and also check for io.EOF
 token, _ := decoder.Token()

 if token == nil {
 break
 }

 switch Element := token.(type) {
 case xml.StartElement:
 if Element.Name.Local == "REACH" {
 fmt.Println("Element name is : ", Element.Name.Local)
 attrName := Element.Attr[0].Name.Local
 attrValue := Element.Attr[0].Value
 fmt.Printf("Attribute name is [%s] and value is [%s] \n", attrName, attrValue)
 }
 }
  }

 }

http://play.golang.org/p/b5RpnKGwsV

References :

https://golang.org/pkg/encoding/xml/#Name

https://golang.org/pkg/encoding/xml/#Attr

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  See also : Golang : delete and modify XML file content



Tags : golang xml newdecoder extract-attribute chardata

By Adam Ng

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