Regular Expressions in JMeter
JMeter includes the pattern matching software [http://jakarta.apache.org/oro/ Apache Jakarta ORO].
There is some documentation for this on the Jakarta web-site.
There is also documentation on an older incarnation of the product at [http://www.savarese.org/oro/docs/OROMatcher/index.html OROMatcher User's guide], which might prove useful.
The pattern matching is very similar to the pattern matching in Perl. A full installation of Perl will include plenty of documentation on regular expressions - look for perlrequick, perlretut, perlre, perlreref. O'Reilly sell a book called "Mastering Regular Expressions" by Jeffrey Friedl which will tell you all you need to know (and a lot more) about regular expressions.
There are also a couple of sample chapters available on their web-site covering REs in Java and .NET, and the Java chapter has a [http://www.oreilly.com/catalog/regex2/chapter/ch08.pdf section on ORO (PDF)] - worth a look.
It is worth stressing the difference between "contains" and "matches", as used on the [http://jakarta.apache.org/jmeter/usermanual/component_reference.html#Response_Assertion Response Assertion] test element:
- "contains" means that the regular expression matched at least some part of the target, so 'alphabet' "contains" 'ph.b.' because the regular expression matches the substring 'phabe'.
- "matches" means that the regular expression matched the whole target. So 'alphabet' is "matched" by 'al.*t'. In this case, it is equivalent to wrapping the regular expression in
$, viz '^al.*t$'. However, this is not always the case. For example, the regular expression 'alp|.lp.*' is "contained" in 'alphabet', but does not match 'alphabet'.
Why? Because when the pattern matcher finds the sequence 'alp' in 'alphabet', it stops trying any other combinations - and 'alp' is not the same as 'alphabet', as it does not include 'habet'.
Note: unlike Perl, there is no need to (i.e. do not) enclose the regular expression in //. So how does one use the Perl modifiers ismx etc if there is no trailing /? The solution is to use Perl5 extended regular expressions, i.e. /abc/i becomes (?i)abc
Links to regex resources
*For an extremely useful Regex tester, see http://weitz.de/regex-coach/*
http://www.visibone.com/regular-expressions/ - quick reference
Suppose you want to match the following portion of a web-page:
name="file" value="readme.txt" and you want to extract
A suitable reqular expression would be:
The special characters above are:
)- these enclose the portion of the match string to be returned
.- match any character.
+- one or more times.
?- don't be greedy, i.e. stop when first match succeeds
Note: without the
.+ would continue past the first
" until it found the last possible
" - probably not what was intended.