Maven enforce no duplicate dependencies even of same version

Question

We can use the maven-enforcer-plugin to prevent duplicate dependencies with difference versions.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-enforcer-plugin</artifactId>
  <version>3.0.0</version>

  <executions>
    <execution>
      <id>no-duplicate-dependencies</id>

      <goals>
        <goal>enforce</goal>
      </goals>

      <configuration>
        <rules>
          <banDuplicatePomDependencyVersions/>
        </rules>
      </configuration>
    </execution>
  </executions>
</plugin>

What about for duplicate dependency declarations of the same version?

Consider that we are building a multi-module project. Say we start with project Foo.

Foo pom.xml

<dependencies>
  <dependency>
    <groupId>someGroup</groupId>
    <artifactId>someArtifact</artifactId>
    <version>1.0.0</version>
  </dependency>
</dependencies>

Later, we introduce the module Bar, which also depends on the same version someArtifact.

Bar pom.xml:

<dependencies>
  <dependency>
    <groupId>someGroup</groupId>
    <artifactId>someArtifact</artifactId>
    <version>1.0.0</version>
  </dependency>
</dependencies>

And Foo depends on Bar, so we update the POM.

Foo pom.xml

<dependencies>
  <dependency>
    <groupId>myGroup</groupId>
    <artifactId>bar</artifactId>
    <version>1.0.0</version>
  </dependency>

  <dependency>
    <groupId>someGroup</groupId>
    <artifactId>someArtifact</artifactId>
    <version>1.0.0</version>
  </dependency>
</dependencies>

As in the above example, and as our projects grow, we may forget that the same version of dependencies are already transitive dependencies.

In my mind, for organization sake, I find it messy to leave these duplicate declarations, such as it is with someArtifact.

I could write a new maven-enforcer-plugin rule, but maybe there is already a solution.

@khmarbaise Yes, thank you. I am looking for a solution that will produce errors. — Oliver, Jun 15 '22 at 14:18
Are you looking to avoid direct dependencies on artifacts that are already transitive dependencies? If so, without the direct dependency, Maven would consider these [used, undeclared dependencies](https://stackoverflow.com/questions/4565740/what-are-unused-undeclared-dependencies-in-maven-what-to-do-with-them), and would discourage that. — Joe, Jun 15 '22 at 14:21
You should check https://maven.apache.org/enforcer/enforcer-rules/banDuplicatePomDependencyVersions.html because that rule should already mentioned that: `Duplicate dependencies are dependencies which have the same group id, artifact id, type and classifier.` ? — khmarbaise, Jun 15 '22 at 15:06

Bikram Pandey · Accepted Answer · 2022-08-10T09:30:45.370

Try with dependencyConvergence rule. Add this to your parent pom.

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-enforcer-plugin</artifactId>
            <version>3.0.0-M3</version>
            <executions>
                <execution>
                    <id>enforce</id>
                    <configuration>
                        <rules>
                            <dependencyConvergence/>
                        </rules>
                    </configuration>
                    <goals>
                        <goal>enforce</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

Reference :: https://maven.apache.org/enforcer/enforcer-rules/dependencyConvergence.html

Maven enforce no duplicate dependencies even of same version

1 Answers1