Break Maven build when there is a dependency conflict

Scenarios

• You want to control #Maven during dependency resolution and break the build if some conditions are not met,
• You want to detect dependencies conflict early during the build,
• You want to avoid anybody in your team to use the dependency x in the version y

This is where the Maven Enforcer Plugin will assist you:

The Enforcer plugin provides goals to control certain environmental constraints such as #Maven version, JDK version and OS family along with many more standard rules and user created rules.

Add in your pom.xml the following to configure the plugin

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-enforcer-plugin</artifactId>
    <version>1.0</version>
    <executions>
        <execution>
            <id>enforce</id>
            <configuration>
                <rules>
                    <DependencyConvergence/>
                </rules>
            </configuration>
            <goals>
                <goal>enforce</goal>
            </goals>
        </execution>
    </executions>
</plugin>

There is a lot of standard rules that are already built in this plugin, the one that is interesting us for controlling dependencies is the dependencyConvergence – ensure all dependencies converge to the same version.

This rule requires that dependency version numbers converge. If a project has two dependencies, A and B, both depending on the same artifact, C, this rule will fail the build if A depends on a different version of C then the version of C depended on by B.

If during the resolution of artifact different version are found the build will fail with some nice logging infromation

Dependency convergence error for org.slf4j:slf4j-api1.6.1 paths to dependency are:  [ERROR] Dependency convergence error for org.slf4j:slf4j-api:1.6.1 paths to dependency are: 
+-org.myorg:my-project:1.0.0-SNAPSHOT   
+-org.slf4j:slf4j-jdk14:1.6.1     
+-org.slf4j:slf4j-api:1.6.1 
and 
+-org.myorg:my-project:1.0.0-SNAPSHOT  
+-org.slf4j:slf4j-nop:1.6.0     
+-org.slf4j:slf4j-api:1.6.0

You can use the standard dependencies management to enforce the version of org.slf4j you are coding/expecting.

In the same category, you can enforce dependencies in another way: force some dependencies to be never use thanks to the rule: bannedDependencies – enforces that excluded dependencies aren’t included. And if you’re are still not satisfied, you can even write your own rules!