Maven doesn't recognize sibling modules when running mvn dependency:tree

94
votes

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...

8
javamavenmaven-2dependencies
Ahhh, The edit is perfect. Why didn't you write this in the first intention? Also, maybe consider changing the title :) I don't mean to be picky, this is just for the sake of clarity and classification. This will help the whole community in the future when searching for a similar issue (which is not crystal clear with the actual title and content that is about dependency:tree) – Pascal Thivent
Hi. Did you find the solution? I have this problem too :( – user168237
Does compilation fail, or just the dependency:tree goal alone? See Don Willis' answer. – metamatt
OMG so in one module if it fails because it cannot find symbols of another module, the other should be added as dependency and installed as JAR? This is the key.... – WesternGun
it's sad maven 3.6 does not solve this problem yet – yuxh

8 Answers

22
votes

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.

112
votes

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.

8
votes

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.

7
votes

Bonusing off the answer from Don Willis:

If your build creates test-jars to share test code among your reactor submodules you should use:

mvn test-compile dependency:tree

which will allow dependency:tree to run to completion in this case.

3
votes

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.

2
votes

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.

2
votes

In a Maven module structure like this:

- parent
  - child1
  - child2

You will have in the parent pom this:

<modules>
  <module>child1</module>
  <module>child2</module>
</modules>

If you now depend on child1 in child2 by putting the following in your <dependencies> in child2:

<dependency>
  <groupId>example</groupId>
  <artifactId>child1</artifactId>
</dependency>

You will receive an error that the JAR for child1 cannot be found. This can be solved by declaring a <dependencyManagement> block including child1 in the pom for parent:

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>example</groupId>
      <artifactId>child1</artifactId>
      <version>${project.version}</version>
    </dependency>
  </dependencies>
</dependencyManagement>

child1 will now be build when you run a compile or package etc. goal on parent, and child2 will find child1's compiled files.

-1
votes

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.