Maven dependency resolution problems caused by child module having a different parent version from top level parent pom.xml

The moral of the story is: When working on a multi-module project,
remember to update ALL pom.xml files, not just one version. Update
from the top-level often.

I'm working on a multi-module Maven project, and Bamboo (our
continuous integration server) is set up so that whenever a release is
done, the version number is incremented.

Now we have most of our dependencies set up in the parent-level
pom.xml. One of them is a client jar to our web services backend. Call
it services-client.jar

I've just spent an afternoon trying to sort out this very confusing
situation where I'd already updated the dependency in our pom.xml to
services-client-19.jar, but whenever I did a build, I would also get
services-client-17.jar.

I thought at first that it was an IDE problem, IntelliJ getting
confused with its caches, so I tried all sorts of fixes at that level
- cleared cache, recreated project file, reimport all Maven projects,
manually delete jars in settings - nothing worked.

I then went to command-line, removed all versions of
services-client*.jar from local repo, then did a build. I grep'd
through all my pom.xml files, and I saw that I only had one reference
to services-client, it was in top-level pom.xml and and it was version
19.


$ find . -name "pom.*" -exec grep -i "0.1203." {} /dev/null \;
./domain/pom.xml: <version>0.1203.0.134-SNAPSHOT</version>
./extension/pom.xml: <version>0.1203.0.134-SNAPSHOT</version>
./front-end/pom.xml: <version>0.1203.0.134-SNAPSHOT</version>
./pom.xml: <version>0.1203.0.138-SNAPSHOT</version>

While this was using services-client-19.jar:

./pom.xml: <version>0.1203.0.138-SNAPSHOT</version>

The child-level modules were pointing to an older parent pom file, one
that Bamboo already installed to our company repository.

The parent version used in the child modules:

./domain/pom.xml: <version>0.1203.0.134-SNAPSHOT</version>

Was using services-client-17.jar

So whenever did "mvn clean install" the project from the
parent-level, Maven was following this sequence when resolving the
dependencies:

1) Maven goes to child modules and builds

2) In /domain/pom.xml - it sees the reference to older parent pom,
fetches from repository, starts to resolve dependencies, fetches older
services client - services-client-17.jar.

3) services-client-17.jar gets installed in local repo

4) During build, code that uses services-client-19.jar code fails
compilation because that jar never actually gets installed until Maven
gets to the top most pom.xml

I haven't verified this with the Maven mailing list yet, this is just
my interpretation of what the problems have been.


The moral of the story is: When working on a multi-module project,
remember to update ALL pom.xml files, not just one version. Update
from the top-level often.


I have updated at the top level and the parent versions are now
consistent - 0.1203.0.140 all the way.

$ find . -name "pom.*" -exec grep -i "0.1203." {} /dev/null \;
./domain/pom.xml: <version>0.1203.0.140-SNAPSHOT</version>
./extension/pom.xml: <version>0.1203.0.140-SNAPSHOT</version>
./front-end/pom.xml: <version>0.1203.0.140-SNAPSHOT</version>
./pom.xml: <version>0.1203.0.140-SNAPSHOT</version>