Maven Checkstyle configLocation ignored?

Question

Attempting to set a custom checkstyle configuration in the maven pom according to the guidelines on the apache site isn't working in a very simple case.

I created a project, MyProject, using the directory layout recommended by Maven (i.e. src/main/java/, src/main/resources), a single file MyClass.java:

package com.myproject;

public class MyClass {

   public static void main(String[] args) {
      System.out.println("This line is longer than 80 characters which returns an error in sun_checks.xml, however my_checks.xml allows for much longer lines and will not return a long line error.");
   }
}

an empty checkstyle file, my_checks.xml:

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">

<module name="Checker">
    <property name="severity" value="warning"/>
    <module name="TreeWalker">
    </module>
</module>

and a pom file according to the specifications in the guide:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.myproject</groupId>
    <artifactId>A_Project</artifactId>
    <name>A Project</name>
    <version>1.0.0</version>

    <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
        <version>2.8</version>
        <configuration>
          <configLocation>my_checks.xml</configLocation>
        </configuration>
      </plugin>
    </plugins>
  </reporting>
</project>

Running 'mvn -X checkstyle:checkstyle' is using the sun_checks.xml (default) instead of using the configuration in the my_checks.xml file, which can be seen by both the resulting checkstyle errors and the debug output (ex. '[DEBUG] request.getConfigLocation() config/sun_checks.xml').

I know the my_checks.xml is valid because the checkstyle.config.location can be changed in the properties using the strategy outlined by Carboni in a previous stack overflow post, but this causes issues when moving to multi-module projects and differs from the 'official' apache maven checkstyle instructions.

Answer 1

Yeah I've found the guidelines on the apache site out of date. Through trawling the internet and scrapping bits together I've managed to work this out.

Moving to the <build> tag worked for a while but when updated to the latest checkstyle it was being ignored again. I've found I had to set a property:

<project ...>

 ....

  <properties>
    <checkstyle.config.location>properties/checkstyle-configuration.xml</checkstyle.config.location>
  </properties>

  <build>
    ...

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
        <version>2.9.1</version>
      </plugin>
    </plugins>
  </build>

  ...

</project>

This is part of my example of how to create your own checkstyle custom check found here:
http://blog.blundellapps.com/create-your-own-checkstyle-check/

and taken from the source code here:
https://github.com/blundell/CreateYourOwnCheckStyleCheck

Answer 2

This works for me when:

1. I place my_checks.xml at the root level (parallel to pom.xml), and
2. Wrap the plugin in the <build> element (as opposed to <reporting>)

With those changes, I see the following:

[DEBUG] Configuring mojo 'org.apache.maven.plugins:maven-checkstyle-plugin:2.8:checkstyle' with basic configurator -->
[DEBUG]   (f) cacheFile = /home/dave/tech/lang/java/web/struts/playground/so/s231_01/target/checkstyle-cachefile
[DEBUG]   (f) configLocation = my_checks.xml
... etc ...
[DEBUG] request.getConfigLocation() my_checks.xml
[DEBUG] The resource 'my_checks.xml' was not found with resourceLoader
... etc ...
[DEBUG] The resource 'my_checks.xml' was not found with resourceLoader org.codehaus.plexus.resource.loader.URLResourceLoader.
[DEBUG] The resource 'my_checks.xml' was not found with resourceLoader org.codehaus.plexus.resource.loader.JarResourceLoader.
[DEBUG] The resource 'my_checks.xml' was found as /home/dave/tech/lang/java/web/struts/playground/so/s231_01/my_checks.xml.

Please reference the usage documentation, specifically:

To specifically configure the Checkstyle Plugin, you need to the add it in the <build> section of your pom.xml as shown in the sample below.

The <reporting> usage is for mvn site.