使用Unmarshal在Go中获取XML名称空间前缀

Question

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.

Answer 1

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.