How to Convert Go Maps to XML: A Custom Marshaler Approach

Marshall Go Maps to XML

Converting Go maps to JSON is straightforward. However, attempting to perform the same operation for XML can lead to an error:

xml: unsupported type: map[string]int

Solution: Using a Custom XML Marshaler

Unlike JSON, XML marshalling does not inherently support maps. To work around this limitation, a custom xml.Marshaler can be implemented for your map type:

<code class="go">// StringMap is a map[string]string.
type StringMap map[string]string

// StringMap marshals into XML.
func (s StringMap) MarshalXML(e *xml.Encoder, start xml.StartElement) error {

    tokens := []xml.Token{start}

    for key, value := range s {
        t := xml.StartElement{Name: xml.Name{"", key}}
        tokens = append(tokens, t, xml.CharData(value), xml.EndElement{t.Name})
    }

    tokens = append(tokens, xml.EndElement{start.Name})

    for _, t := range tokens {
        err := e.EncodeToken(t)
        if err != nil {
            return err
        }
    }

    // flush to ensure tokens are written
    return e.Flush()
}</code>

Now, you can simply call xml.MarshalIndent(...) to marshal the map into XML:

<code class="go">output, err := xml.MarshalIndent(data, "", "  ")</code>

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