Regular Expression to check String is valid XHTML or not

Question

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regular expression to check if string is valid XML

I am looking Regular Expression to check String is Valid XHTML or not

example

<h2>Legal HTML Entity References</h2><table align="center" border="0" ><tr></tr></table>

You really need read something about Chomsky language hierarchy and formal grammars. You can check only regular language with regular expression and the XHTML is not regular language. [1]: http://en.wikipedia.org/wiki/Formal_grammar#The_Chomsky_hierarchy — Robert Balent, Sep 27 '11 at 07:48

score 5 · Answer 1 · edited May 23 '17 at 12:34

5

This sounds like a bad idea: The language of valid XHTML strings is not regular.

Use an HTML parsing library instead. A few examples:

Related question:

edited May 23 '17 at 12:34

Community

answered Sep 27 '11 at 07:44

aioobe

score 1 · Answer 2 · answered Sep 27 '11 at 07:44

Regex is exactly the wrong tool to use.

HTML is not a regular language and hence cannot be parsed by regular expressions.

Since you've tagged this post Java, you should look at using one of the myriad of HTML parsing libraries available.

score 1 · Answer 3 · edited May 23 '17 at 11:55

1

Have a look here why parsing HTML using regular expressions won't work reliably: RegEx match open tags except XHTML self-contained tags

XHTML is just another flavor/superset of HTML, so you're better of using a real validator, like JTidy etc.

edited May 23 '17 at 11:55

Community

answered Sep 27 '11 at 07:46

Thomas

score 0 · Answer 4 · answered Sep 27 '11 at 07:47

0

Try to check it with a parser. Don't do it the Cthulhu Way.

Here you can find a strating point and some examples on how to do it: The Java XML Validation API

answered Sep 27 '11 at 07:47

Xavi López

4 Answers4