如何在XML字符串中获取“ <”和“>”？

Question

Is it posible to get '<' and '>' value in this XML string? I have problem with unmarshal, and I can't change the strings. Is there anyone who can help me in this? Here my code:

package main

import (
    "encoding/xml"
    "fmt"
)

func main() {
    type Example struct {
        XMLName xml.Name `xml:"Shop"`
        ShopName  string `xml:"ShopName"`
    }

    myString1 := `<Shop> 
        <ShopName>Fresh Fruit <Fruit Shop></ShopName>
    </Shop>`

    myString2 :=`<Shop> 
        <ShopName>Fresh Fruit < Fruit Shop ></ShopName>
    </Shop>`

    //example 1
    var example1 Example
    err := xml.Unmarshal([]byte(myString1), &example1)
    if err != nil {
        fmt.Println("error: %example1", err)
    }else{
        fmt.Println(example1.ShopName)
    }       

    //example 2
    var example2 Example
    err = xml.Unmarshal([]byte(myString2), &example2)
    if err != nil {
        fmt.Printf("error: %example2", err)
        return
    }else{
        fmt.Println(example2.ShopName)
    }
}

I get an error bellow:

error: %example1 XML syntax error on line 2: attribute name without = in element
error: &{%!e(string=expected element name after <) %!e(int=2)}xample2

What I want to get:

Fresh Fruit <Fruit Shop>
Fresh Fruit < Fruit Shop >

Answer 1

The input you have is definitely invalid XML. There is a bug in the creation routine of the XML.

Idea

Since you say you have to deal with it the way it is... here a suggestion:

1. replace all closing tags via regex to something you will basically never have in your input (e.g. @#lt#@/tagname@#gt#@). While doing that save all the distinct tag names to a slice.
2. With the slice of tag names replace the start tags
3. Now escape all remaining < and >
4. Last but not least replace the original tags back: @#lt#@ to < and @#gt#@ to >

Now you should have valid xml that is parseable.

Proof of Concept

Playground

package main

import (
    "bytes"
    "fmt"
    "log"
    "regexp"
    "sort"
)

var (
    rlt = []byte("@#lt#@")
    rgt = []byte("@#gt#@")
    lt  = []byte("<")
    gt  = []byte(">")
)

// used for sorting strings by length
type ByLength []string

func (s ByLength) Len() int {
    return len(s)
}
func (s ByLength) Swap(i, j int) {
    s[i], s[j] = s[j], s[i]
}
func (s ByLength) Less(i, j int) bool {
    return len(s[i]) < len(s[j])
}

func main() {
    s := `<Shop>
    <ShopName>Fresh Fruit <Fruit Shop></ShopName>
    <ShopName attr="val1">Fresh Fruit <Shop test></ShopName>
</Shop>`

    r1, err := regexp.Compile("</([^<>]*)>")
    if err != nil {
        log.Fatal(err)
    }

    names := []string{}
    out := r1.ReplaceAllFunc([]byte(s), func(b []byte) []byte {
        name := b[2 : len(b)-1]

        // TODO: only append name if not already in list
        names = append(names, string(name))

        // probably optimizable
        bytes := make([]byte, 0, len(name)+12)
        bytes = append(bytes, rlt...)
        bytes = append(bytes, name...)
        bytes = append(bytes, rgt...)
        return bytes
    })

    // sort names descending by length otherwise we risk replacing parts of names like with <Shop and <ShopName
    sort.Sort(sort.Reverse(ByLength(names)))

    for _, name := range names {
        // replace only exact start tags
        out = bytes.Replace(out, []byte(fmt.Sprintf("<%s>", name)), []byte(fmt.Sprintf("@#lt#@%s@#gt#@", name)), -1)

        // replace start tags with attributes
        r3, err := regexp.Compile(fmt.Sprintf("<%s( [^<>=]+=\"[^<>]+)>", name))
        if err != nil {
            // handle error
        }
        out = r3.ReplaceAll(out, []byte(fmt.Sprintf("@#lt#@%s$1@#gt#@", name)))
    }

    out = bytes.Replace(out, []byte{'<'}, lt, -1)
    out = bytes.Replace(out, []byte{'>'}, gt, -1)

    out = bytes.Replace(out, rlt, []byte{'<'}, -1)
    out = bytes.Replace(out, rgt, []byte{'>'}, -1)

    fmt.Println(string(out))
}

Notes

1. this is a proof of concept. This is not optimised for performance.
2. you might still run into content that might not be escaped properly. Then you will need to further optimise. If there is something like this in the content it will be falsely considered a tag: <tagname> or <tagname something ="something>. Therefore expect some xml to still to be invalid. Log invalid xml so you can improve the algorithm.