找不到未编组的XML节点

Question

I'm trying to unmarshal an XML file, but it's not finding my root node snapshot, which is keeping me from being able to unmarshal the rest of my file.

I'm calling parser.go from main.go, as well as the Validate function.

parser.go

type Parser struct {
    file     *ConfigXML
    filepath string
}

//Load the file
func (parser *Parser) Load() error {
    b, err := helpers.LoadFile(parser.filepath)

    if err != nil {
        return err
    }

    parser.file = nil
    xml.Unmarshal(b, &parser.file)

    return nil
}

func (parser *Parser) Validate() error {

    if len(parser.file.snapshot) == 0 {
        return fmt.Errorf("node snapshot does not exist")
    }

    return nil
}

While my XML file is large, I'll post a snippet:

<?xml version='1.0' encoding='UTF-8'?>
 <snapshot>
  <ENBEquipment id="233443234543" model="XYZ" version="LR_16_02_L">
   <attributes>
    <administrativeState>unlocked</administrativeState>
   </attributes>
  </ENBEquipment>
 </snapshot>

The structs I've created to unmarshal to:

type ConfigXML struct {
    snapshot []Snapshot
    FileName string
}

// Snapshot is root <snapshot>
type Snapshot struct {
    ENBEquipment []ENBEquipment
}

// ENBEquipment subtag of <snapshot> -> <ENBEquipment>
type ENBEquipment struct {
    ID              string `xml:"id,attr"`
    DeviceName      string `xml:"id,attr"`
    SoftwareVersion string `xml:"version,attr"`
    ElementType     string `xml:"model,attr"`
    Enb             []Enb
}

However when I attempt to run with go run main.go, I get:

ERRO[2018-06-12 09:45:34] parsing failed    error="node snapshot does not exist" filename=/tmp/datain/xyz/123/agg/233443234543.xml

If I take out the Validation of snapshot, the file unmarshals fine. Why is this not finding the node?

Answer 1

Try exporting snapshot and adding a struct tag indicate the name.

xml.Unmarshal uses reflection to populate the the struct. So, the elements of the struct need to be exported.

type ConfigXML struct {
    Snapshot []Snapshot `xml:"snapshot"`
    FileName string
}

See the GoDoc (search for "exported" and check out the example) for additional information about how xml.Unmarshal works.