Maven doesn't recognize sibling modules when r

Question

I'm trying to set up a multi-module Maven project, and the inter-module dependencies are apparently not being set up correctly.

I have:

<modules>
  <module>commons</module>
  <module>storage</module>
</modules>

in the parent POM (which has a packaging-type pom) and then subdirectories commons/ and storage/ which define JAR poms with the same name.

Storage depends on Commons.

In the main (master) directory, I run mvn dependency:tree and see:

[INFO] Building system
[INFO]    task-segment: [dependency:tree]
[INFO] ------------------------------------------------------------------------
[INFO] [dependency:tree {execution: default-cli}]
[INFO] domain:system:pom:1.0-SNAPSHOT
[INFO] \- junit:junit:jar:3.8.1:test
[INFO] ------------------------------------------------------------------------
[INFO] Building commons
[INFO]    task-segment: [dependency:tree]
[INFO] ------------------------------------------------------------------------
[INFO] [dependency:tree {execution: default-cli}]
...correct tree...
[INFO] ------------------------------------------------------------------------
[INFO] Building storage
[INFO]    task-segment: [dependency:tree]
[INFO] ------------------------------------------------------------------------
Downloading: http://my.repo/artifactory/repo/domain/commons/1.0-SNAPSHOT/commons-1.0-SNAPSHOT.jar
[INFO] Unable to find resource 'domain:commons:jar:1.0-SNAPSHOT' in repository my.repo (http://my.repo/artifactory/repo)
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Failed to resolve artifact.

Missing:
----------
1) domain:commons:jar:1.0-SNAPSHOT

Why does the dependency on "commons" fail, even though the reactor has obviously seen it because it successfully processes its dependency tree? It should definitely not be going to the 'net to find it as it's right there...

The pom for storage:

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <packaging>jar</packaging>
  <parent>
    <artifactId>system</artifactId>
    <groupId>domain</groupId>
    <version>1.0-SNAPSHOT</version>
  </parent>
  <groupId>domain</groupId>
  <artifactId>storage</artifactId>
  <name>storage</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <!-- module dependencies -->
    <dependency>
      <groupId>domain</groupId>
      <artifactId>commons</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>

    <!-- other dependencies -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

Thanks for any suggestions!

(Edit)

To clarify, what I am looking for here is this: I don't want to have to install module X to build module Y which depends on X, given that both are modules referenced from the same parent POM. This makes intuitive sense to me that if I have two things in the same source tree, I shouldn't have to install intermediate products to continue the build. Hopefully my thinking makes some sense here...

Answer 1

As discussed in this maven mailing list thread, the dependency:tree goal by itself will look things up in the repository rather than the reactor. You can work around this by mvn installing, as previously suggested, or doing something less onerous that invokes the reactor, such as

mvn compile dependency:tree

Works for me.

Answer 2

Realizing this is an older thread but it seems that either the tool evolved or this might have been missed the first time around.

It is possible to perform a build that makes dependencies resolved without installing by doing a reactor build.

If you start your build in the parent that describes the module structure of your project then your dependencies between your modules will be resolved during the build itself through the internal Maven reactor.

Of course this is not the perfect solution since it does not solve the build of a single individual module within the structure. In this case Maven will not have the dependencies in his reactor and will bee looking to resolve it in the repository. So for individual builds you still have to install the dependencies first.

Here is some reference describing this situation.

Answer 3

for me, what led me to this thread was a similar problem and the solution was to ensure all module dependency pom's had

 <packaging>pom</packaging>

the parent had

pom

my model dep had pom - so there was no jar to be found.

Answer 4

The only thing that workd for me : switching to gradle :(

I have

Parent
  +---dep1
  +---war1 (using dep1)

and I can just cd in war1 and use mvn tomcat7:run-war. I always have to install the whole project before, despite war1 references his parent and the parent references war1 and dep1 (as modules) so all dependencies should be known.

I don't understand what the problem is.

Answer 5

Make sure the module which is failing gets resolved in the pom, is pointing to the right parent by including the configurations in the pom file of the module.

Answer 6

I think the problem is that when you specify a dependency Maven expects to have it as jar (or whatever) packaged and available from at least a local repo. I'm sure that if you run mvn install on your commons project first everything will work.