jacoco : Cannot exclude classes

Question

I have a maven project and I want to use jacoco for code coverage. Here is the relevant section of my pom

Answer 1

Property excludes of report goal specifies which files should be excluded from analysis during generation of report. In case of /path/tp/my/project/target/classes/META-INF/bundled-dependencies/some-third-party-1-jar-with-dependencies.jar@org/slf4j/event/EventConstants.class file is /path/tp/my/project/target/classes/META-INF/bundled-dependencies/some-third-party-1-jar-with-dependencies.jar , and the rest is about class in JAR file.

Therefore as one of examples of correct configuration:

  
    META-INF/**
  

As a proof having pom.xml

  4.0.0

  org.example
  example
  1.0-SNAPSHOT

  
    UTF-8
  

  
    
      junit
      junit
      4.12
      test
    
  

  
    
      
        org.jacoco
        jacoco-maven-plugin
        0.8.1
      
    
  

src/main/java/Example.java

public class Example {
}

and src/test/java/ExampleTest.java

public class ExampleTest {
  @org.junit.Test
  public void test() {
  }
}

Execution of

mvn clean jacoco:prepare-agent package
mkdir target/classes/META-INF/
cp ~/.m2/repository/org/slf4j/slf4j-api/1.4.2/slf4j-api-1.4.2.jar target/classes
cp ~/.m2/repository/org/slf4j/slf4j-api/1.7.7/slf4j-api-1.7.7.jar target/classes/META-INF
mvn jacoco:report

will fail with message

Error while analyzing /private/tmp/j/target/classes/slf4j-api-1.4.2.jar@org/slf4j/helpers/BasicMarker.class. Can't add different class with same name: org/slf4j/helpers/BasicMarker

while same execution with pom.xml containing exclusion of META-INF/**

  4.0.0

  org.example
  example
  1.0-SNAPSHOT

  
    UTF-8
  

  
    
      junit
      junit
      4.12
      test
    
  

  
    
      
        org.jacoco
        jacoco-maven-plugin
        0.8.1
        
          
            META-INF/**
          
        
      
    
  

will succeed.

As a side note: semantic of property excludes of prepare-agent goal is different - it specifies class names (regardless of their on-disk location) that should be excluded from instrumentation during execution of tests.