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.