We face an issue when a same artifact-X
is transitively brought by a dependency-1
with provided scope, and another dependency-2
with default (compile) scope.
This artifact-X
will be computed as compile scope, while we expect it to be explicitly provided by dependency-1
.
For example, dependency-1
pom contains:
<dependencies>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.7</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.1</version>
</dependency>
</dependencies>
dependency-2
pom contains:
<dependencies>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.8</version>
</dependency>
</dependencies>
Assembly project pom contains:
<dependencies>
<!-- do not include dependencies already provided by module-1 at runtime -->
<dependency>
<groupId>com.company</groupId>
<artifactId>module-1</artifactId>
<version>1.0</version>
<scope>provided</scope>
</dependency>
<!-- get dependencies required by module-2 runtime -->
<dependency>
<groupId>com.company</groupId>
<artifactId>module-2</artifactId>
<version>1.0</version>
</dependency>
</dependencies>
But a mvn dependency:tree
on assembly project will output:
[INFO] --- maven-dependency-plugin:3.1.0:tree (show-app-dependencies) @ module-3 ---
[INFO] com.company:module-3:pom:1.0
[INFO] +- com.company:module-1:jar:1.0:provided
[INFO] | +- org.apache.commons:commons-lang3:jar:3.7:compile
[INFO] | \- org.apache.commons:commons-collections4:jar:4.1:provided
[INFO] \- com.company:module-2:jar:1.0:compile
And we can see the artifact commons-lang3:jar:3.7
which come from dependency-1 is now at compile scope. Note that we don't use any <dependencyManagement>
here.
This is very confusing, and leads to duplicate libraries in runtime classpath when dependency-1
is effectively provided in classpath of dependency-2
runtime (for example by an application server).
Moreover, based on Maven documentation about dependency mediation/scope, the transitive dependencies that are provided should be always ommited.
http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html#Dependency_Scope
It seems to be a bug, that maven-3.6 does not handle, which is a shame !
However, as our goal is simply to package ONLY the libraries defined as compile/runtime (and ignore all the provided ones, and their transitives), how to achieve this using dependency management, or if impossible, using maven-assembly-plugin ??