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JMeter example source code file (regular_expressions.xml)

This example JMeter source code file (regular_expressions.xml) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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a, apache, expressions, jmeter, jmeter, license, license, note, oro, regular, regular, the, the, there

The JMeter regular_expressions.xml source code

<?xml version="1.0"?>
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   (the "License"); you may not use this file except in compliance with
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<!DOCTYPE document
[
<!ENTITY sect-num '20'>
]>
<document prev="functions.html" next="hints_and_tips.html" date="$Date: 2010-07-02 00:38:04 +0100 (Fri, 02 Jul 2010) $">

<properties>
  <title>User's Manual: Regular Expressions
</properties>

<body>

<section name="§-num;. Regular Expressions" anchor="regex">
<subsection name="§-num;.1 Overview" anchor="overview">
<p>
JMeter includes the pattern matching software <a href="http://jakarta.apache.org/oro/">Apache Jakarta ORO
<br/>
There is some documentation for this on the Jakarta web-site, for example 
<a href="http://jakarta.apache.org/oro/api/org/apache/oro/text/regex/package-summary.html">
a summary of the pattern matching characters</a>
</p>
<p>
There is also documentation on an older incarnation of the product at 
<a href="http://www.savarese.org/oro/docs/OROMatcher/index.html">OROMatcher User's guide, which might prove useful. 
</p>
<p>
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.
</p>
<p>
It is worth stressing the difference between "contains" and "matches", as used on the Response Assertion test element:
</p>
<ul>
<li>
"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'.
</li>
<li>
"matches" means that the regular expression matched the whole target. 
So 'alphabet' is "matched" by 'al.*t'. 
</li>
</ul>
<p>In this case, it is equivalent to wrapping the regular expression in ^ and $, viz '^al.*t$'. 
</p>
<p>However, this is not always the case. 
For example, the regular expression 'alp|.lp.*' is "contained" in 'alphabet', but does not match 'alphabet'.
</p>
<p>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'.
</p>
<p>
Note: unlike Perl, there is no need to (i.e. do not) enclose the regular expression in //. 
</p>
<p>
So how does one use the modifiers ismx etc if there is no trailing /? 
The solution is to use <i>extended regular expressions, i.e. /abc/i becomes (?i)abc.
See also <a href="placement">Placement of modifiers below.
</p>
</subsection>
<subsection name="§-num;.2 Examples" anchor="examples">
<h3>Extract single string
<p>
Suppose you want to match the following portion of a web-page: 
<br/>
<code>name="file" value="readme.txt">
<br/>
and you want to extract <code>readme.txt.
<br/>
A suitable regular expression would be:
<br/>
<code>name="file" value="(.+?)">
<p>
The special characters above are:
</p>
<ul>
<li>( and ) - these enclose the portion of the match string to be returned
<li>. - match any character
<li>+ - one or more times 
<li>? - don't be greedy, i.e. stop when first match succeeds
</ul>
<p>
Note: without the ?, the .+ would continue past the first <code>">
until it found the last possible <code>"> - which is probably not what was intended.
</p>
<p>
Note: although the above expression works, it's more efficient to use the following expression:
<br/>
<code>name="file" value="([^"]+)">
where<br>

[^"] - means match anything except "<br>

In this case, the matching engine can stop looking as soon as it sees the first <code>", 
whereas in the previous case the engine has to check that it has found <code>"> rather than say " >.
</p>
<h3>Extract multiple strings
<p>
Suppose you want to match the following portion of a web-page:<br/>
<code>name="file.name" value="readme.txt" 
and you want to extract both <code>file.name and readme.txt.
<br/>
A suitable reqular expression would be:
<br/>
<code>name="([^"]+)" value="([^"]+)"
<br/>
This would create 2 groups, which could be used in the JMeter Regular Expression Extractor template as $1$ and $2$.
</p>
<p>
The JMeter Regex Extractor saves the values of the groups in additional variables.
</p>
<p>
For example, assume:
</p>
<ul>
<li>Reference Name: MYREF
<li>Regex: name="(.+?)" value="(.+?)"
<li>Template: $1$$2$
</ul>
<note>Do not enclose the regular expression in / /
<p>
The following variables would be set:
</p>
<ul>
<li>MYREF: file.namereadme.txt
<li>MYREF_g0: name="file.name" value="readme.txt"
<li>MYREF_g1: file.name
<li>MYREF_g2: readme.txt
</ul>
These variables can be referred to later on in the JMeter test plan, as ${MYREF}, ${MYREF_g1} etc 
</p>
</subsection>
<subsection name="§-num;.3 Line mode" anchor="line_mode">
<p>The pattern matching behaves in various slightly different ways, 
depending on the setting of the multi-line and single-line modifiers.
Note that the single-line and multi-line operators have nothing to do with each other;
they can be specified independently.
</p>
<h3>Single-line mode
<p>
Single-line mode only affects how the '.' meta-character is interpreted.
</p>
<p>
Default behaviour is that '.' matches any character except newline. 
In single-line mode, '.' also matches newline.
</p>

<h3>Multi-line mode
<p>
Multi-line mode only affects how the meta-characters '^' and '$' are interpreted.
</p>
<p>
Default behaviour is that '^' and '$' only match at the very beginning and end of the string. 
When Multi-line mode is used, the '^' metacharacter matches at the beginning of every line,
and the '$' metacharacter matches at the end of every line.</p>

</subsection>

<subsection name="§-num;.4 Meta characters" anchor="meta_chars">
<p>
Regular expressions use certain characters as meta characters - these characters have a special meaning to the RE engine.
Such characters must be escaped by preceeding them with \ (backslash) in order to treat them as ordinary characters.
Here is a list of the meta characters and their meaning (please check the ORO documentation if in doubt).
</p>
<ul>
<li>( ) - grouping
<li>[ ] - character classes
<li>{ } - repetition
<li>* + ? - repetition
<li>. - wild-card character
<li>\ - escape character
<li>| - alternatives
<li>^ $ - start and end of string or line
</ul>
<p>Please note that ORO does not support the \Q and \E meta-characters.
[In other RE engines, these can be used to quote a portion of an RE so that the meta-characters stand for themselves.]</p>
</subsection>

<subsection name="§-num;.5 Placement of modifiers" anchor="placement">
<p>
Modifiers can be placed anywhere in the regex, and apply from that point onwards.
[A bug in ORO means that they cannot be used at the very end of the regex.
However they would have no effect there anyway.]
</p>
<p>
The single-line (?s) and multi-line (?m) modifiers are normally placed at the start of the regex.
</p>
<p>
The ignore-case modifier (?i) may be usefully applied to just part of a regex,
for example:
<pre>
Match ExAct case or (?i)ArBiTrARY(?-i) case
</pre>
</p>
</subsection>
</section>

<section name="§-num;.6 Testing Regular Expressions" anchor="testing_expressions">
<p>
There is a <a href="http://jakarta.apache.org/oro/demo.html">demo applet for Apache JMeter ORO.
</p>
<p>
Another approach is to use a simple test plan to test the regular expressions.
The Java Request sampler can be used to generate a sample, or the HTTP Sampler can be used to load a file.
Add a Debug Sampler and a Tree View Listener and changes to the regular expression can be tested quickly,
without needing to access any external servers. 
</p>
</section>

</body>
</document>

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