Maven dependency:tree is not showing all transitive dependencies

Question

I have trouble understanding the behaviour of the depencendy:tree output. When running the plugin on a higher module, I am missing vital information from modules it depends on. But when I run the plugin on the lower module I can see the depencendies. Here is an example to show the problem (names changed):

mvn -pl foo:bar-application dependency:tree -Dincludes=foo:*
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building bar-application 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.1:tree (default-cli) @ bar-application ---
[INFO] foo:bar-application:ear:0.0.1-SNAPSHOT
[INFO] +- foo:bar-business:ejb:0.0.1-SNAPSHOT:compile
[INFO] |  +- foo:common-util:jar:0.0.1-SNAPSHOT:compile
...
[INFO] +- foo:bar-web:war:0.0.1-SNAPSHOT:compile
[INFO] \- foo:common-logging:jar:0.0.1-SNAPSHOT:compile
[INFO] ------------------------------------------------------------------------

The tree shows a depencendy to bar-web, but only one further depencendy from bar-web to other projects (common-logging).

But bar-web has far more dependencies:

mvn -pl foo:bar-web dependency:tree -Dincludes=foo:*
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building bar-web 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.1:tree (default-cli) @ bar-web ---
[INFO] foo:bar-web:war:0.0.1-SNAPSHOT
[INFO] +- foo:common-logging:jar:0.0.1-SNAPSHOT:compile
[INFO] +- foo:culprit-business-client:jar:0.0.1-SNAPSHOT:compile
...
[INFO] +- foo:common-rest:jar:0.0.1-SNAPSHOT:compile
[INFO] |  \- foo:config-business-client:jar:0.0.1-SNAPSHOT:compile
[INFO] \- foo:bar-business:jar:0.0.1-SNAPSHOT:provided
[INFO]    \- foo:some-client:jar:0.0.1-SNAPSHOT:provided
[INFO] ------------------------------------------------------------------------

Why are the other dependencies not shown when inspecting bar-application? It took me a while of searching to find the culprit. Im a using

mvn --version
Apache Maven 3.0.5

Answer 1

A WAR includes its dependencies inside the archive, that's why Maven does not propagate them transitively to other artifacts depending on the WAR artifact.

Answer 2

mvn dependency:tree

shows you the effective dependencies, as in where your actual dependencies come from.

mvn dependency:tree -Dverbose

will show you all transitive dependencies including the reasonwhy they are excluded