What is the regular expression to check empty XML nodes?

Question

I get an xml node;

<p:FirstAddressLine1></p:FirstAddressLine1>

I want to rewrite that node, if it has an empty string/null. I used ^$ but it fails to validate that particular xml node contains empty string.

Anyone knows , what im doing wrong here? and the right regular expression to be used?

What language are you writing in? Show us the code snippet that you using to match. — merlin2011, May 23 '14 at 23:37
Possible duplicate of http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags — Pillsy, May 23 '14 at 23:56
@CasimiretHippolyte i need to test xml nodes come with empty. Then i want to add some default values. — Ratha, May 23 '14 at 23:59
@merlin2011 i'm using an Java based application server, it will support regular expressions when we provide in the configuration file. So, here i provide particular expression, but seems failing. The underlying language is java — Ratha, May 23 '14 at 23:59
@Ratha, Is the match supposed to be against the inside of the tag? — merlin2011, May 24 '14 at 00:06
My idea is to test if there is one character at least, instead of testing if there is no character at all. — Casimir et Hippolyte, May 24 '14 at 00:06
@CasimiretHippolyte checking for one character perfectly works. Thanks a lot. — Ratha, May 24 '14 at 00:07
@merlin2011 didnt get you. But i found solution as CasmiretHippolyte said — Ratha, May 24 '14 at 00:08
However, be careful with newlines that don't match the dot. Use the dotall mode if possible, or the javascript trick `[\s\S]` instead. — Casimir et Hippolyte, May 24 '14 at 00:09

score 1 · Answer 1 · answered May 23 '14 at 23:47

I would use something like the following regex

(?:<p:FirstAddressLine1>(?!<\/p))

Is uses a Negative Lookahead, and will match <p:FirstAddressLine1> followed by anything other then </p. If it sees a </p directly after the first <> it will not match the string.

EXAMPLE USAGE

use strict;
use warnings;

my @lines = <DATA>;

foreach (@lines) {

    if ( $_ =~ m/(?:<p:FirstAddressLine1>(?!<\/p))/ ) {
        print "The string is NOT empty\n";

    }
    else {
        print "The string is empty\n";
    }

}

__DATA__
<p:FirstAddressLine1></p:FirstAddressLine1>
<p:FirstAddressLine1>TEST</p:FirstAddressLine1>

RESULT

The string is empty
The string is NOT empty

Im not directly using java. Im configuring an Appserver which is java based — Ratha, May 24 '14 at 00:01

What is the regular expression to check empty XML nodes?

1 Answers1