Go语言XML解组：处理非标准日期格式的time.Time字段

package main

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

// CustomTime 类型，用于处理非标准日期格式的XML元素
type CustomTime struct {
    time.Time
}

// UnmarshalXML 实现了 xml.Unmarshaler 接口，用于自定义解析XML日期字符串
func (ct *CustomTime) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
    const dateFormatLayout = "20060102" // 对应 "yyyymmdd" 格式

    var v string
    // 解码XML元素内容到字符串v
    if err := d.DecodeElement(&v, &start); err != nil {
        return fmt.Errorf("failed to decode XML element into string: %w", err)
    }

    // 使用time.Parse根据指定布局解析日期字符串
    parsedTime, err := time.Parse(dateFormatLayout, v)
    if err != nil {
        return fmt.Errorf("failed to parse date string '%s' with layout '%s': %w", v, dateFormatLayout, err)
    }

    // 将解析后的time.Time赋值给CustomTime的嵌入字段
    *ct = CustomTime{parsedTime}
    return nil
}

// Transaction 结构体，包含需要自定义解析的日期字段
type Transaction struct {
    XMLName         xml.Name `xml:"Transaction"`
    Id              int64    `xml:"sequencenumber"`
    ReferenceNumber string   `xml:"ourref"`
    Description     string   `xml:"description"`
    Type            string   `xml:"type"`
    CustomerID      string   `xml:"namecode"`
    DateEntered     CustomTime `xml:"enterdate"` // 使用 CustomTime 类型
    Gross           float64  `xml:"gross"`
    // 为了简化示例，TransactionDetailContainer 被注释掉
    // Container       TransactionDetailContainer `xml:"subfile"`
}

func main() {
    // 模拟的XML数据，其中日期格式为 "yyyymmdd"
    xmlData := `
        <Transaction>
            <sequencenumber>12345</sequencenumber>
            <ourref>REF-ABC-001</ourref>
            <description>Payment for services</description>
            <type>SALE</type>
            <namecode>CUST001</namecode>
            <enterdate>20231026</enterdate>
            <gross>123.45</gross>
        </Transaction>`

    var transaction Transaction
    // 使用 xml.Unmarshal 进行解组
    err := xml.Unmarshal([]byte(xmlData), &transaction)
    if err != nil {
        fmt.Printf("Error unmarshalling XML: %v\n", err)
        return
    }

    fmt.Println("XML Unmarshal Successful!")
    fmt.Printf("ID: %d\n", transaction.Id)
    fmt.Printf("Reference Number: %s\n", transaction.ReferenceNumber)
    fmt.Printf("Description: %s\n", transaction.Description)
    fmt.Printf("Type: %s\n", transaction.Type)
    fmt.Printf("Customer ID: %s\n", transaction.CustomerID)
    fmt.Printf("Date Entered (CustomTime): %v\n", transaction.DateEntered)
    // 可以直接访问嵌入的 time.Time 值
    fmt.Printf("Date Entered (time.Time value): %v\n", transaction.DateEntered.Time) 
    fmt.Printf("Gross: %.2f\n", transaction.Gross)

    // 尝试一个错误的日期格式，验证错误处理
    xmlDataInvalidDate := `
        <Transaction>
            <sequencenumber>67890</sequencenumber>
            <enterdate>2023-10-26</enterdate> <!-- 错误的日期格式 -->
            <gross>50.00</gross>
        </Transaction>`

    var invalidTransaction Transaction
    err = xml.Unmarshal([]byte(xmlDataInvalidDate), &invalidTransaction)
    if err != nil {
        fmt.Printf("\nError unmarshalling XML with invalid date format (expected): %v\n", err)
    } else {
        fmt