Unmarshaling XML in Go | 易学教程

问题

I have the following xml "file":

<pinnacle_line_feed>
    <PinnacleFeedTime>1439954818555</PinnacleFeedTime>
    <lastContest>34317132</lastContest>
    <lastGame>218491030</lastGame>
    <events>
        <event>
            <event_datetimeGMT>2015-08-21 09:50</event_datetimeGMT>
            <gamenumber>483406220</gamenumber>
            <sporttype>Aussie Rules</sporttype>
            <league>AFL</league>
            <IsLive>No</IsLive>
            <participants>
                <participant>
                    <participant_name>Hawthorn Hawks</participant_name>
                    <contestantnum>1251</contestantnum>
                    <rotnum>1251</rotnum>
                    <visiting_home_draw>Visiting</visiting_home_draw>
                    </participant>
                <participant>
                    <participant_name>Port Adelaide Power</participant_name>
                    <contestantnum>1252</contestantnum>
                    <rotnum>1252</rotnum>
                    <visiting_home_draw>Home</visiting_home_draw>
                </participant>
            </participants>
            <periods></periods>
        </event>
    </events>
</pinnacle_line_feed>

I am attempting to parse this with Golang, and have written the below thus far:

package main
import (
	"fmt"
	"encoding/xml"
)

type Participant struct {
	XMLName            xml.Name `xml:"participant"`
	participant_name   string `xml:"participant_name"`
	contestantnum      int `xml:"contestantnum"`
	rotnum             int `xml:"rotnum"`
	visiting_home_draw string `xml:"visiting_home_draw"`
}

type Event struct {
	XMLName           xml.Name `xml:"event"`
	event_datetimeGMT string `xml:"event_datetimeGMT"`
	gamenumber        string `xml:"gamenumber"`
	sporttype         string `xml:"sporttype"`
	league            string `xml:"league"`
	IsLive            string `xml:"IsLive"`
	Participant       []Participant `xml:"participant"`
}

type Events struct {
	XMLName xml.Name `xml:"events"`
	Event   []Event `xml:"event"`
}

type Pinnacle_Line_Feed struct {
	XMLName          xml.Name `xml:"pinnacle_line_feed"`
	PinnacleFeedTime string `xml:"PinnacleFeedTime"`
	lastContest      string `xml:"lastContest"`
	lastGame         string `xml:"lastGame"`
	Events           []Events `xml:"events"`
}

Frankly, I have researched quite a bit on deep nested xml parsing in Golang, and I haven't found much to help with the Unmarshal portion of this code. Ideally, the code would return something similar to a python dictionary, such as,

{event_datetimeGMT: 2015-08-21, gamenumber: 483406220, ... , visiting_home_draw: "Home"}

EDIT:

Based on Nicolas's comment below, I added the following. This runs without error, but produces an empty result.

 func main() {
         pinny_xml := `
         <pinnacle_line_feed>
            <PinnacleFeedTime>1439954818555</PinnacleFeedTime>
            <lastContest>34317132</lastContest>
            <lastGame>218491030</lastGame>
            <events>
                <event>
                    <event_datetimeGMT>2015-08-21 09:50</event_datetimeGMT>
                    <gamenumber>483406220</gamenumber>
                    <sporttype>Aussie Rules</sporttype>
                    <league>AFL</league>
                    <IsLive>No</IsLive>
                    <participants>
                        <participant>
                            <participant_name>Hawthorn Hawks</participant_name>
                            <contestantnum>1251</contestantnum>
                            <rotnum>1251</rotnum>
                            <visiting_home_draw>Visiting</visiting_home_draw>
                            </participant>
                        <participant>
                            <participant_name>Port Adelaide Power</participant_name>
                            <contestantnum>1252</contestantnum>
                            <rotnum>1252</rotnum>
                            <visiting_home_draw>Home</visiting_home_draw>
                        </participant>
                    </participants>
                    <periods></periods>
                </event>
            </events>
        </pinnacle_line_feed>
        `

        xmlReader := bytes.NewReader([]byte(pinny_xml))
        yourPinnacleLineFeed := new(Pinnacle_Line_Feed)
        if err := xml.NewDecoder(xmlReader).Decode(yourPinnacleLineFeed); err != nil {
            return // or log.Panic(err.Error()) if in main
        }
}

回答1:

You can do it like this :

xmlReader := bytes.NewReader([]byte(your_xml_as_a_string_here))
yourPinnacleLineFeed := new(Pinnacle_Line_Feed)
if err := xml.NewDecoder(xmlReader).Decode(yourPinnacleLineFeed); err != nil {
    return // or log.Panic(err.Error()) if in main
}

This is if your xml "file" is a string. If you're getting it from the internet (as the body of an http response for instance), resp.Body is already going to satisfy a Reader, so you can skip the first line. If you're opening a real file on the OS, you can also open it as a Reader, same thing.

EDIT: Two more things:

You can nest the structs and drop the xml.Name fields for simplicity and clarity
I also noticed you forgot the participants level in the structs, leading for no participants to be unmarshaled

Here's a more simple version that works, with an optional function to check what you have inside the results :

package main

import (
    "bytes"
    "encoding/json"
    "encoding/xml"
    "fmt"
    "log"
)

type Pinnacle_Line_Feed struct {
    PinnacleFeedTime string `xml:"PinnacleFeedTime"`
    LastContest      string `xml:"lastContest"`
    LastGame         string `xml:"lastGame"`
    Events           struct {
        Event []struct {
            Event_datetimeGMT string `xml:"event_datetimeGMT"`
            Gamenumber        string `xml:"gamenumber"`
            Sporttype         string `xml:"sporttype"`
            League            string `xml:"league"`
            IsLive            string `xml:"IsLive"`
            Participants      struct {
                Participant []struct {
                    Participant_name   string `xml:"participant_name"`
                    Contestantnum      int    `xml:"contestantnum"`
                    Rotnum             int    `xml:"rotnum"`
                    Visiting_home_draw string `xml:"visiting_home_draw"`
                } `xml:"participant"`
            } `xml:"participants"`
        } `xml:"event"`
    } `xml:"events"`
}

func main() {
    pinny_xml := `
         <pinnacle_line_feed>
            <PinnacleFeedTime>1439954818555</PinnacleFeedTime>
            <lastContest>34317132</lastContest>
            <lastGame>218491030</lastGame>
            <events>
                <event>
                    <event_datetimeGMT>2015-08-21 09:50</event_datetimeGMT>
                    <gamenumber>483406220</gamenumber>
                    <sporttype>Aussie Rules</sporttype>
                    <league>AFL</league>
                    <IsLive>No</IsLive>
                    <participants>
                        <participant>
                            <participant_name>Hawthorn Hawks</participant_name>
                            <contestantnum>1251</contestantnum>
                            <rotnum>1251</rotnum>
                            <visiting_home_draw>Visiting</visiting_home_draw>
                        </participant>
                        <participant>
                            <participant_name>Port Adelaide Power</participant_name>
                            <contestantnum>1252</contestantnum>
                            <rotnum>1252</rotnum>
                            <visiting_home_draw>Home</visiting_home_draw>
                        </participant>
                    </participants>
                    <periods></periods>
                </event>
            </events>
        </pinnacle_line_feed>
    `

    xmlReader := bytes.NewReader([]byte(pinny_xml))
    yourPinnacleLineFeed := new(Pinnacle_Line_Feed)
    if err := xml.NewDecoder(xmlReader).Decode(yourPinnacleLineFeed); err != nil {
        log.Panic(err.Error())
    }

    printX(yourPinnacleLineFeed)
}

func printX(x interface{}) (err error) {
    var xBytes []byte
    xBytes, err = json.MarshalIndent(x, "", "  ")
    if err != nil {
        return
    }
    fmt.Println(string(xBytes))
    return
}

回答2:

You need to uppercase all of the fields in your structs. The xml decoder needs the fields to be exported in order to work properly. Go playground here.

来源：https://stackoverflow.com/questions/32125816/unmarshaling-xml-in-go

标签

xml