Golang encoding/xml
From wikinotes
go's builtin library for parsing xml.
See also: golang encoding, xml, golang x/net
A more detailed introduction to go's encoding interface can be seen in golang encoding/json.
NOTE:
Golang's builtin xml library does not support schema validation.
Documentation
official docs https://pkg.go.dev/encoding/xml@go1.18.3
Tutorials
tutorialedge https://tutorialedge.net/golang/parsing-xml-with-golang/
Struct Tags
See full details here
type User struct { Name `xml:"Name"` // <User><Name>value</Name></User> Color `xml:"color,attr"` // <User color="value"></User> Skip `xml:"-"` // <User></User> }XML namespaces are supported, by providing a prefix to the xml tag.
type Html struct { XMLName xml.Name `xml:"http://www.w3.org/1999/xhtml html` } // <html xmlns="http://www.w3.org/1999/xhtml"> // <!-- ... --> // </html>Known issues:
- schema validation does not appear to be supported
Serialization
Basics
type User struct { Id int `xml:"id"` Name string `xml:"name,attr"` } func main() { user := User{123, "will"} bytes, _ := xml.Marshal(&user) fmt.Println(string(bytes)) // <User name="will"><id>123</id></User> }You can also marshall with an indent
xml.MarshallIndent( &user, " ", // (2) indent entire object this many spaces " ", // (4) indent-width ) //| | <-- 2x spaces // <User name="will"> // <id>123</id> // <-- indented 4x spaces // </User>
Deserialization
Basics
type User struct { Id int `xml:"id"` Name string `xml:"name,attr"` } func main() { raw := `<User name="will"><id>123</id></User>` var user User xml.Unmarshall([]byte(raw), &user) fmt.Println(user) }Non-Homogenous XML
XML is generally not homogenous.
Record each possible sub-element as a field on your object.
If an element can occur multiple times, declare it as an array.
You can ignore elements by not defining fields for them.encoded := ` <mediawiki> <siteinfo> abc </siteinfo> <page> <title>Main Page</title> </page> <page> <title>Linux</title> </page> </mediawiki> ` type Result struct { XMLName xml.Name `xml:"mediawiki"` // root node SiteInfo string `xml:"siteinfo"` // only one 'siteinfo' element under 'mediawiki' Page []Page `xml:"page"` // multiple 'page' elements under 'mediawiki' } type Page struct { Title string `xml:"title"` } var result Result xml.Unmarshall([]byte(encoded), &result) fmt.Println(result.Page[0].Title.Text) // LinuxArbitrary XML
type Node struct { XMLName xml.Name Attrs []*xml.Attr `xml:",any,attr"` // each attr.Name, attr.Value Data string `xml:",chardata"` // 'Title' in <h1>Title</h1> Nodes []*Node `xml:",any"` // child-nodes } // deserialize var parsed Node xml.Unmarshal([]byte(raw), &parsed) // re-serialize bytes, err := xml.Marshal(&parsed)Example: Deserialize, Modify, Re-serialize an arbitrary xml object.
WARNING:
Do not parse HTML with XML (elements like
<br/>are invalid XML).import ( "encoding/xml" "fmt" ) type Node struct { XMLName xml.Name Attrs []*xml.Attr `xml:",any,attr"` // each attr.Name, attr.Value Data string `xml:",chardata"` // 'Title' in <h1>Title</h1> Nodes []*Node `xml:",any"` // child-nodes } func addDotHtmlToAHrefs(node *Node) { // Adds a '.html' suffix to each href in a '<a href="foo">foo</a>' if node.XMLName.Local == "a" { for _, attr := range node.Attrs { if attr.Name.Local == "href" { attr.Value = fmt.Sprint(attr.Value, ".html") } } } for _, child := range node.Nodes { addDotHtmlToAHrefs(child) } } func main() { // define xml raw := `<html> <p><a href="abc">ABC</a></p> <blockquote><p><a href="def">DEF</a></p></blockquote> </html>` // unmarshall var parsed Node xml.Unmarshal([]byte(raw), &parsed) // modify addDotHtmlToAHrefs(&parsed) // re-marshall, modified bytes, _ := xml.MarshalIndent(&parsed, "", " ") fmt.Println(string(bytes)) }Outputs
<html> <p> <a href="abc.html">ABC</a> </p> <blockquote> <p> <a href="def.html">DEF</a> </p> </blockquote> </html>
Custom Deserializers
TODO:
finish
func (revision *Revision) UnmarshalXML(d *xml.Decoder, start xml.Startelement) error { return nil }
