XPath – how to create a custom rule

By , last updated July 11, 2016

After I began to use PMD and tried to write my first custom XPath rules, I realised that there aren’t very much information about it. So I needed to figure out almost everything by myself. Here I’ll try to explain what I’ve figured out.

I use Eclipse 3.5 to run the rules, by the way.

1. Create a new ruleset file as described here.
2. Check if you need a special encoding for the language you are going to use. I was using a norwegian language, so I needed to add encoding=”ISO-8859-1″ to xml header:

<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
...

3.Begin writing a custom rule:

<rule name="MoreThanOneLoggUtil"
      message="You are using more that one LoggUtil instance. Only one is legal."
      class="net.sourceforge.pmd.rules.XPathRule"
      externalInfoUrl="">
<description>
   You are using more that one LoggUtil instance. Only one is legal.
</description>
<priority>4</priority>
<properties>
   <property name="xpath">
       <value>
          ... (some XPath code here) ...
       </value>
   </property>
</properties>
<example>
<![CDATA[
public class Foo
     private LoggUtil log = new LoggUtil(Foo.class);
     private LoggUtil log2 = new LoggUtil(Foo.class);
]]>
</example>
</rule>

Senior Software Engineer developing all kinds of stuff.

Comments

  1. Robert W. February 20, 2015 Leave a Reply

    Great howto! Thank you (and c&p 😉 )

    Btw: You are missing an equal sign in ‘name”MoreThanOneLoggUtil”‘.

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