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.
Here is a concrete example.
This will cause a build to fail.
<dependencies> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-jdk14</artifactId> <version>1.6.1</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-nop</artifactId> <version>1.6.0</version> </dependency> </dependencies>
With this being logged during compilation
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
And this will succeed.
<dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-jdk14</artifactId> <version>1.6.1</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-nop</artifactId> <version>1.6.0</version> <exclusions> <exclusion> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> </exclusion> </exclusions> </dependency>
Here is how a project should be setup to use this rule
<project> ... <build> <plugins> ... <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-enforcer-plugin</artifactId> <version>1.4</version> <executions> <execution> <id>enforce</id> <configuration> <rules> <dependencyConvergence/> </rules> </configuration> <goals> <goal>enforce</goal> </goals> </execution> </executions> </plugin> ... </plugins> </build> ... </project>
By default the non-unique versions are matched, which means the X.Y-SNAPSHOT instead of the timestamped versions. If you want to use the unique versions of the dependencies, you can set its property to true.
<dependencyConvergence> <uniqueVersions>true</uniqueVersions> </dependencyConvergence>