CODEWITHSUNDEEP
xmlgo
yageek
yageek

Reputation: 4465

Get XML namespace prefix in Go using Unmarshal

I would like to know if it is possible to get the XML namespace prefix using the Unmarshal method in encoding/xml.

For example, I have: 

<application xmlns="http://wadl.dev.java.net/2009/02" xmlns:xs="http://www.w3.org/2001/XMLSchema">
</application>

I would like to know how to retrieve the xs defining the prefix for XMLSchema, without having to use the Token method.

Upvotes: 2

Views: 4954

Answers (2)

yageek
yageek

Reputation: 4465

Currently (Go 1.5), it does not seems to be possible.

The only solution I found, was to use rewind the element:

func NewDocument(r io.ReadSeeker) (*Document, error) {

    decoder := xml.NewDecoder(r)

    // Retrieve xml namespace first
    rootToken, err := decoder.Token()


    if err != nil {
        return nil, err
    }

    var xmlSchemaNamespace string

    switch element := rootToken.(type) {
    case xml.StartElement:

        for _, attr := range element.Attr {
            if attr.Value == xsd.XMLSchemaURI {
                xmlSchemaNamespace = attr.Name.Local
                break
            }
        }
    }

    /* Process name space */

    // Rewind
    r.Seek(0, 0)

    // Standart unmarshall
    decoder = xml.NewDecoder(r)
    err = decoder.Decode(&w)

    /* ... */
}

Upvotes: 0

Ainar-G
Ainar-G

Reputation: 36249

Just get it like every other attribute:

type App struct {
    XS string `xml:"xs,attr"`
}

Playground: http://play.golang.org/p/2IOmkX1Jov.

It gets trickier if you also have an actual xs attribute, sans xmlns. Even if you add the namespace URI to XS's tag, you will probably get an error.

EDIT: If you want to get all declared namespaces, you can define a custom UnmarshalXML on your element and scan it's attributes:

type App struct {
    Namespaces map[string]string
    Foo        int `xml:"foo"`
}

func (a *App) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
    a.Namespaces = map[string]string{}
    for _, attr := range start.Attr {
        if attr.Name.Space == "xmlns" {
            a.Namespaces[attr.Name.Local] = attr.Value
        }
    }

    // Go on with unmarshalling.
    type app App
    aa := (*app)(a)
    return d.DecodeElement(aa, &start)
}

Playground: http://play.golang.org/p/u4RJBG3_jW.

Upvotes: 3

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