How to use regular expressions to verify XML document format in golang

In golang, regular expressions can be used to easily verify whether the format of an XML document conforms to the specified specification. This article will introduce how to use regular expressions to verify the format of XML documents.

XML is a markup language used for writing documents with structured data. XML documents are composed of tags and data. Tags are used to identify the type and structure of data. The format of XML documents must follow certain specifications, otherwise it will cause parsing errors or data errors.

Generally speaking, the format verification of XML documents can be defined using special document types such as DTD or XSD. However, if you only need to verify that the basic format of an XML document is correct, using regular expressions is a simpler approach.

The following is how to use regular expressions to verify the format of XML documents:

Step 1. Define regular expressions
First, we need to define a regular expression to verify the format of XML documents . This regular expression needs to match the following requirements:

1. The XML document must start with "
2. followed by is a version number, the format is "version="1.0"", 1.0 in the version number can be replaced by other version numbers;
3. There can be one or more spaces or newlines after the version number, and then "?>" terminator;
4. Then there is an empty document type declaration in the format of "", where xxx is the document type name;
5. Document There can be one or more spaces or newlines after the type declaration;
6. Finally is a root element in the format of "", where xxx is the element name.

To sum up, we can define a regular expression as follows:

var xmlRe = regexp.MustCompile(`^<?xml(s)+version="([^"]+)"(s)*?>((s)*<!DOCTYPE(.+)>)?(s)*<([^s]+)(.*?)>(.|
)*</8>(s)*$`)

Step 2. Use regular expressions to verify XML documents
We can use this regular expression To verify whether the format of an XML document is correct. The specific method is as follows:

func IsValidXML(xml string) bool {
    return xmlRe.MatchString(xml)
}

The above code defines an IsValidXML function, which accepts an XML string as a parameter and returns true or false, indicating whether the format of the XML document is correct. This function uses the regular expression defined above for matching and returns true if the match is successful, otherwise it returns false.

The following is a complete example:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    xml := `


    Tove
    Jani
    Reminder
    Don't forget me this weekend!
`

    isValid := IsValidXML(xml)
    fmt.Println(isValid)
}

var xmlRe = regexp.MustCompile(`^<?xml(s)+version="([^"]+)"(s)*?>((s)*<!DOCTYPE(.+)>)?(s)*<([^s]+)(.*?)>(.|
)*</8>(s)*$`)

func IsValidXML(xml string) bool {
    return xmlRe.MatchString(xml)
}

The output result is true, indicating that the format of this XML document is correct.

Summary
By using regular expressions, we can easily verify whether the format of an XML document is correct. However, it should be noted that this regular expression can only verify the basic format of the XML document, but cannot check the legality of elements and attributes. Therefore, when performing XML data operations, it is recommended to use dedicated document type definitions for verification.

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