Go Encoding Xml

The encoding/xml package is used for parsing XML-formatted data into a struct.

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Example

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Struct Tags

Unmarshal maps an XML element to a struct using the tags of struct fields and the following hierarchy of rules:

1. If the struct has tag ",innerxml" and type []byte or string, Unmarshal accumulates the raw XML nested inside that element in that field. The rest of the rules still apply.

2. If the struct has a field named XMLName of type xml.Name, Unmarshal stores that element's name in that field.

3. If the XMLName field has an associated tag of the form "name" or "namespace-URL name", that element must have the given name (and name space) or Unmarshal will return an error.

4. If an attribute matches a field with an associated tag containing ",attr", Unmarshal maps that attribute to that field.

5. If an attribute did not match the previous rule and there is a field with tag ",any,attr", Unmarshal maps that attribute to the first such field.

6. Character data accumulates in the first field that has tag ",chardata" and type []byte or string.

   • If there is no such field, character data is discarded.

7. Comments accumulate in the first field that has tag ",comment" and type []byte or string.

   • If there is no such field, comments are discarded.

8. If a sub-element matches the prefix of a tag formatted as "a" or "a>b>c", Unmarshal descends into the XML structure looking for sub-elements with the given names, and will map the innermost elements to that field.

   • ">a" is equivalent to "a"

9. If a sub-element matches a field's XMLName tag and the field has no explicit name tag, Unmarshal maps that sub-element to struct field.

10. If a sub-element matches a field without any mode flags (",attr", ",chardata", etc), Unmarshal maps that sub-element to that field.

11. If a sub-element hasn't matched any of the above rules and there is a field with tag ",any", Unmarshal maps that sub-element to that field.

12. An anonymous field is handled as if the fields of its value were part of the outer struct.

13. A field with tag "-" is never used.

Element Fields

Names for fields can be set by any of:

• matching the name of the struct field to the XML element name

• using an XML tag like xml:"name"

• using a XMLName field of type xml.Name with the above pattern

As an example:

type Html struct {
  head    Head
  Body    Body     `xml:"body"`
  XMLName xml.Name `xml:"html"`
}

Note that this is purely a demonstration; fields need to be public, so head should be capitalized.

Attribute fields

Names for attributes can be set by any of:

• matching the name of the struct field to the attribu8te name with the ",attr" tag

• using an XML tag like xml:"name,attr"

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