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 Tips for Maven 2 Checkstyle Plugin
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Tips for Maven 2 Checkstyle Plugin

* Multimodule Configuration.

  Configuring the Checkstyle plugin for use within a large multimodule projects can be done, but will require a little setup.

  Example will use a mysterious project called 'whizbang'.

-------------------
[whizbang]$ ls
drwxr-xr-x+ 5      0 Nov  3 15:36 core/
drwxr-xr-x+ 6      0 Nov 16 16:11 gui/
drwxr-xr-x+ 6      0 Nov 29 13:13 jmx/
-rw-r--r--  1   6153 Nov 29 13:08 pom.xml
drwxr-xr-x+ 4      0 Nov  1 15:48 src/
-------------------

  First: setup a sub project to house your build tools.

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[whizbang]$ ls
drwxr-xr-x+ 4      0 Nov 29 13:44 build-tools/
drwxr-xr-x+ 5      0 Nov  3 15:36 core/
drwxr-xr-x+ 6      0 Nov 16 16:11 gui/
drwxr-xr-x+ 6      0 Nov 29 13:13 jmx/
-rw-r--r--  1   6153 Nov 29 13:08 pom.xml
drwxr-xr-x+ 4      0 Nov  1 15:48 src/
-------------------

  Next, include the resources you want in the build-tools jar file.

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[whizbang/build-tools]$ find . -type f
./pom.xml
./src/main/resources/whizbang/checkstyle.xml
./src/main/resources/whizbang/pmd.xml
./src/main/resources/whizbang/LICENSE.txt
-------------------

  TIP: put the resources into a subdirectory that you can ensure will be unique, and not conflict with anyone else.

  Now, include the checkstyle configuration in the top level pom.xml

-------------------
[whizbang]$ cat pom.xml
<?xml version="1.0" encoding="UTF-8"?>

<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.example.whizbang</groupId>
  <artifactId>whizbang-parent</artifactId>
  <version>1.0</version>
  <packaging>pom</packaging>
  <name>WhizBang Parent</name>

  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
        <configuration>
          <configLocation>whizbang/checkstyle.xml</configLocation>
          <headerLocation>whizbang/LICENSE.txt</headerLocation>
        </configuration>
      </plugin>
    </plugins>
  </reporting>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
		<dependencies>
		  <dependency>
		    <groupId>com.example.whizbang</groupId>
		    <artifactId>build-tools</artifactId>
		    <version>1.0</version>
		  </dependency>
		</dependencies>
      </plugin>
    </plugins>
  </build>
  <modules>
    <module>build-tools</module>
    <module>core</module>
    <module>jmx</module>
    <module>gui</module>
  </modules>
</project>
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  Once you are done with that, ensure that you do not include the maven-checkstyle-plugin in your sub modules, as their definition and configuration, will override the top level parent pom's definition.

  Lastly, kick off a build of the site.

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[whizbang]$ mvn site
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  Every sub project will use the same checkstyle setup and configuration.