I use Saxon EE APIs to validate XML payload with XSDs. My environment is OSGi. One of my user is trying to escape @ character in regex definition. I've shared the snippet of the line which is causing issue.
<xsd:restriction base="xsd:string">
<xsd:pattern value=".+\@.+\..+"/>
</xsd:restriction>
This causes the following error while loading the xsd (inside saxon library).
Error at xsd:pattern on line 17 column 70
Syntax error at char 4 in regular expression: Escape character '@' not allowed
Could anyone please share any hints on how to overcome this issue? Please let me know, if the complete xsd is required.
The XSD rules for regular expressions are rather stricter than those in many other regex dialects: characters can only be escaped if they actually need to be escaped and if the escape sequence has a defined meaning. There's no escape character defined for \@ so it should simply be written as @.
The reason for the rule is for forwards compatibility: it allows new escape characters to be introduced in the future without breaking existing schemas.