useDefaultResourceIgnoreList flag

By default, the duplicate finder plugin ignores a set of resources on the classpath which tend to be duplicates all the time.

These resources are specified as standard Java regular expressions. All patterns are case insensitive.

The default resource ignore list is documented here.

Maven command line property: duplicate-finder.useDefaultResourceIgnoreList (Plugin version 1.1.1+)

Default: true

Warning! Setting this element to false will result in a significant number of false positives.

useDefaultClassIgnoreList flag

Available in plugin version 1.2.1 and later.

By default, the duplicate finder plugin ignores a set of classes on the classpath which tend to be duplicates all the time.

These resources are specified as standard Java regular expressions. All patterns are case insensitive.

The default class ignore list is documented here.

Maven command line property: duplicate-finder.useDefaultClassIgnoreList

Default: true

ignoredResourcePatterns for global resource exclusion

The ignoredResourcePatterns element lists standard Java regular expression patterns that are excluded from the duplicate check. All patterns are treated as case insensitive.

Any pattern added here is treated similar to the patterns on the default resource ignore list.

Note. Any pattern here is applied to the whole resource path, not to sub-components. It is therefore important to anchor a pattern to the beginning, the end or a separator (/). It is recommended to test any regular expression with a regular expression tester.

<configuration>
  <ignoredResourcePatterns>
    <ignoredResourcePattern>.*index\.html$</ignoredResourcePattern>
  </ignoredResourcePatterns>
</configuration>

<configuration>
  <ignoredResourcePatterns>
    <ignoredResourcePattern>/?[^/]*?log4j\.xml$</ignoredResourcePattern>
    <ignoredResourcePattern>/?[^/]*?log4j\.properties$</ignoredResourcePattern>
    <ignoredResourcePattern>/?[^/]*?logback\.xml$</ignoredResourcePattern>
    <ignoredResourcePattern>/?[^/]*?logback\.properties$</ignoredResourcePattern>
  </ignoredResourcePatterns>
</configuration>

ignoredClassPatterns for global resource exclusion

Available in plugin version 1.2.1 and later.

The ignoredClassPatterns element lists standard Java regular expression patterns that are excluded from the duplicate check. All patterns are treated as case insensitive.

Any pattern added here is treated similar to the patterns on the default resource ignore list.

Note. Any pattern here is applied to the whole resource path, not to sub-components. It is therefore important to anchor a pattern to the beginning, the end or a separator (/). It is recommended to test any regular expression with a regular expression tester.

<configuration>
  <ignoredClassPatterns>
    <ignoredClassPattern>javax.*$</ignoredClassPattern>
  </ignoredClassPatterns>
</configuration>

<configuration>
  <ignoredClassPatterns>
    <ignoredClassPattern>^((?!com[/.]mycompany).*)$</ignoredClassPattern>
  </ignoredClassPatterns>
</configuration>

ignoredDependencies for global dependency exclusion

Sometimes, a dependency is hopeless. It may drag in a large number of duplicates or it may not have been written to any given standard. For these very rare cases, it is possible to completely exclude a dependency and everything that is related to it from the duplication check. Usually, these dependencies are also in a non-standard scope (such as provided or system).

Warning! Excluding a dependency globally may make the duplicate finder check pass. It will not, however, fix the underlying cause for the failure. Ignoring duplicate dependencies can and almost always will lead to hard-to-debug runtime problems such as hard-to-explain ClassNotFoundException (or their big sibling NoClassDefFoundError) problems.

The ignoredDependencies section contains [dependency](Describing Dependencies) elements. Each dependency can be fully or partially defined.

Each element listed here will be removed from the list of dependencies that are checked for duplicates.

<!-- jRuby is hopeless -->
<configuration>
  <ignoredDependencies>
    <dependency>
      <groupId>org.jruby</groupId>
      <artifactId>jruby-complete</artifactId>
    </dependency>
  </ignoredDependencies>
</configuration>