How to use JMH Gradle Plugin with Shadow Plugin

Question

Optionally it is possible to use Shadow Plugin to do actual JMH jar creation. The configuration of Shadow Plugin for JMH jar is done via jmhJar block. For example:

build.gradle

jmhJar {
  append('META-INF/spring.handlers')
  append('META-INF/spring.schemas')
  exclude 'LICENSE'
}

Duplicate dependencies and classes

This plugin will merge all dependencies that are defined as part of jmh, runtime and optionally testRuntime configurations into a single set from which fat jar will be created when executing jmhJar task. This is done to ensure that no duplicate dependencies will be added the generated jar.

In addition plugin applies DuplicatesStrategy defined via duplicateClassesStrategy extension property to every class while creating fat jar. By default this property is set to DuplicatesStrategy.FAIL which means that upon detection of duplicate classes the task will fail.

It is possible to change this behavior by configuring duplicateClassesStrategy property via jmh block, e.g.:

build.gradle

jmh {
  duplicateClassesStrategy = 'warn'
}

However if you do encounter problem with defaut value it means that the classpath or sources in your project do contain duplicate classes which means that it is not possible to predict which one will be used when fat jar will generated.