Trying to parse xml in golang but getting empty struct

Question

im trying to parse an xml:

attaching xml since its too long for herehttps://drive.google.com/file/d/1CPleC1gBAR6n7lcyiR_zVMEjkowo3gUU/view?usp=sharing

type L1CProduct struct {
    XMLName xml.Name `xml:"n1:Level-1C_User_Product"`
    N1GeneralInfo N1GeneralInfo `xml:"n1:General_Info"`
}

type N1GeneralInfo struct {
    XMLName xml.Name `xml:"n1:General_Info"`
    ProductInfo ProductInfo `xml:"Product_Info"`
    SpectralInformationList SpectralInformationList `xml:"Product_Image_Characteristic>Spectral_Information_List"`
}

type SpectralInformationList struct {
    XMLName xml.Name `xml:"Spectral_Information_List"`
    SpectralInformation []SpectralInformation `xml:"Spectral_Information"`
}

type SpectralInformation struct {
    XMLName xml.Name `xml:"Spectral_Information"`
    BandId string `xml:"bandId,attr"`
    PhysicalBand string `xml:"physicalBand,attr"`
}

type ProductInfo struct{
    XMLName xml.Name `xml:"Product_Info"`
    ProductStartTime string `xml:"PRODUCT_START_TIME"`
    GenerationTime string `xml:"GENERATION_TIME"`
    ProductUri string `xml:"PRODUCT_URI"`

}

func parseXml() {
    // Open our xmlFile

    // xmlPath := inProcessPath + "/MTD_MSIL1C.xml"
    xmlPath := "/home/htc/Lizer/backend/InProcessResults/MTD_MSIL1C.xml"
    xmlFile, err := os.Open(xmlPath)
    // if we os.Open returns an error then handle it
    if err != nil {
        fmt.Println(err)
    }

    fmt.Println("Successfully Opened " + xmlPath)
    // defer the closing of our xmlFile so that we can parse it later on
    defer xmlFile.Close()

    // read our opened xmlFile as a byte array.
    byteValue, _ := ioutil.ReadAll(xmlFile)
    fmt.Printf("\nData: %s", byteValue)
    // we initialize our Users array
    var users L1CProduct
    // we unmarshal our byteArray which contains our
    // xmlFiles content into 'users' which we defined above
    xml.Unmarshal(byteValue, &users)
    fmt.Println(users.N1GeneralInfo.ProductInfo.ProductStartTime + "º")
    println(users.N1GeneralInfo.SpectralInformationList.SpectralInformation[1].BandId)
    // we iterate through every user within our users array and
    // print out the user Type, their name, and their facebook url
    // as just an example
    // for i := 0; i < len(users.N1GeneralInfo.SpectralInformationList.SpectralInformation); i++ {
    // for i := 0; i < 10; i++ {
    //     fmt.Println("Band Id: " + users.N1GeneralInfo.SpectralInformationList.SpectralInformation[i].BandId)
    //     fmt.Println("physicalBand: " + users.N1GeneralInfo.SpectralInformationList.SpectralInformation[i].PhysicalBand)
    // }

}

but while the file is read correctly mi xml structures are empty

fmt.Println(users.N1GeneralInfo.ProductInfo.ProductStartTime + "º")
    println(users.N1GeneralInfo.SpectralInformationList.SpectralInformation[1].BandId)

fmt.Println(users.N1GeneralInfo.ProductInfo.ProductStartTime + "º")
println(users.N1GeneralInfo.SpectralInformationList.SpectralInformation[1].BandId)

its like the struct is empty: output : **

º panic: runtime error: index out of range goroutine 1 [running]: main.parseXml() /home/htc/Lizer/backend/app/pkg/Services/Bandwith/service.go:164 +0x3fd main.main() /home/htc/Lizer/backend/app/pkg/Services/Bandwith/service.go:53 +0x20**

exit status 2

I suggest you try to reduce your problem by using a small XML file, simple tag names and then post the full code here. — topskip
– topskip, Commented Nov 10, 2022 at 19:12

Para · Accepted Answer · 2022-11-11 06:36:19Z

if you want parser : in xml

like

xml:"n1:Level-1C_User_Product"

should be:

xml:"https://psd-14.sentinel2.eo.esa.int/PSD/User_Product_Level-1C.xsd Level-1C_User_Product"

see: Parse Xml in GO for atttribute with ":" in tag

follow is a demo:

package main

import (
    "encoding/xml"
    "fmt"
    "os"
)

type L1CProduct struct {
    XMLName       xml.Name `xml:"https://psd-14.sentinel2.eo.esa.int/PSD/User_Product_Level-1C.xsd Level-1C_User_Product"`
    N1GeneralInfo N1GeneralInfo
}

type N1GeneralInfo struct {
    XMLName     xml.Name    `xml:"https://psd-14.sentinel2.eo.esa.int/PSD/User_Product_Level-1C.xsd General_Info"`
    ProductInfo ProductInfo `xml:"Product_Info"`
}
type ProductInfo struct {
    XMLName          xml.Name `xml:"Product_Info"`
    ProductStartTime string   `xml:"PRODUCT_START_TIME"`
    GenerationTime   string   `xml:"GENERATION_TIME"`
    ProductUri       string   `xml:"PRODUCT_URI"`
}

func parseXml() {
    // Open our xmlFile

    // xmlPath := inProcessPath + "/MTD_MSIL1C.xml"
    xmlPath := "./MTD_MSIL1C.xml"
    // read our opened xmlFile as a byte array.
    byteValue, _ := os.ReadFile(xmlPath)
    // we initialize our Users array
    var users L1CProduct

    err := xml.Unmarshal(byteValue, &users)
    if err != nil {
        fmt.Printf("%v\n", err)
    }
    fmt.Println(users.N1GeneralInfo.ProductInfo.ProductStartTime + "º")
}

func main() {
    parseXml()
}

follow is output:

2022-11-09T16:55:19.024Zº

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