Finding the root directory of a multi module Maven reactor project

Maven Problem Overview

Is there an easy way to find the root of a multi-module Maven project, like Gradle's rootDir?

Background:

I want to use the maven-dependency-plugin to copy artifacts from all sub-modules of my multi-module project to a directory that is relative to the root directory of the entire project.

That is, my layout looks similar to this, names changed:

to-deploy/
my-project/
    module-a/
    module-b/
    more-modules-1/
        module-c/
        module-d/
    more-modules-2/
        module-e/
        module-f/
    ...

And i want all the artifacts to be copied from the target-directories of their respective modules to my-project/../to-deploy so i end up with

to-deploy/
    module-a.jar
    module-b.jar
    module-c.jar
    module-d.jar
    module-e.jar
    module-f.jar
my-project/
    ...

I could do it with a relative path in each module, like so:

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>copy</id>
                    <phase>install</phase>
                    <goals>
                        <goal>copy</goal>
                    </goals>
                    <configuration>
                        <artifactItems>
                            <artifactItem>
                                <groupId>${project.groupId}</groupId>
                                <artifactId>${project.artifactId}</artifactId>
                                <version>${project.version}</version>
                                <type>jar</type>
                                <outputDirectory>../../to-deploy</outputDirectory>
                            </artifactItem>
                        </artifactItems>
                    </configuration>
                </execution>
            </executions>
        </plugin>

But i'd rather not specify a relative path in the <outputDirectory> element. I'd prefer something like ${reactor.root.directory}/../to-deploy, but i can't find anything like this.

Also, i'd prefer if there was some way to inherit this maven-dependency-plugin configuration so i don't have to specify it for each module.

I also tried inheriting a custom property from the root pom:

<properties>
    <myproject.root>${basedir}</myproject.root>
</properties>

But when i tried to use ${myproject.root} in the module POM's, the ${basedir} would resolve to the basedir of the module.

Also, i found http://labs.consol.de/lang/de/blog/maven/project-root-path-in-a-maven-multi-module-project/ where it's suggested that each developer and presumably the continuous integration server should configure the root directory in a profiles.xml file, but i don't consider it a solution.

So is there an easy way to find the root of a multi-module project?

Maven Solutions

Solution 1 - Maven

use `${session.executionRootDirectory}`

For the record, ${session.executionRootDirectory} works for me in pom files in Maven 3.0.3. That property will be the directory you're running in, so run the parent project and each module can get the path to that root directory.

I put the plugin configuration that uses this property in the parent pom so that it's inherited. I use it in a profile that I only select when I know that I'm going to run Maven on the parent project. This way, it's less likely that I'll use this variable in an undesired way when I run Maven on a child project (because then the variable would not be the path to the parent).

For example,

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-dependency-plugin</artifactId>
    <executions>
        <execution>
            <id>copy-artifact</id>
            <phase>package</phase>
            <goals>
                <goal>copy</goal>
            </goals>
            <configuration>
                <artifactItems>
                    <artifactItem>
                        <groupId>${project.groupId}</groupId>
                        <artifactId>${project.artifactId}</artifactId>
                        <version>${project.version}</version>
                        <type>${project.packaging}</type>
                    </artifactItem>
                </artifactItems>
                <outputDirectory>${session.executionRootDirectory}/target/</outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>

Solution 2 - Maven

Since Maven 3.3.1, you can use ${maven.multiModuleProjectDirectory} for this purpose. (thanks to https://stackoverflow.com/a/48879554/302789)

edit: this seems to only work properly when you have a .mvn folder at the root of your project.

Solution 3 - Maven

Something which I have used in my projects is to override the property in the sub-module poms.

    root:           <myproject.root>${basedir}</myproject.root>
moduleA:        <myproject.root>${basedir}/..</myproject.root>
other/moduleX:  <myproject.root>${basedir}/../..</myproject.root>

This way you still have the relative paths, but you can define a plugin once in the root module, and your modules will inherit it with the right substitution for myproject.root.

Solution 4 - Maven

There is a maven plugin that solves this particular problem: directory-maven-plugin

It will assign the root path of your project to a property of your choosing. See highest-basedir goal in the docs.

For example:

<!-- Directory plugin to find parent root directory absolute path -->
<plugin>
  <groupId>org.commonjava.maven.plugins</groupId>
  <artifactId>directory-maven-plugin</artifactId>
  <version>0.1</version>
  <executions>
    <execution>
      <id>directories</id>
      <goals>
        <goal>highest-basedir</goal>
      </goals>
      <phase>initialize</phase>
      <configuration>
        <property>main.basedir</property>
      </configuration>
    </execution>
  </executions>
</plugin>

Then use ${main.basedir} anywhere in your parent / child pom.xml.

Solution 5 - Maven

As others have suggested, directory-maven-plugin is the way to go. However, I found it works best with the directory-of goal, as described here: https://stackoverflow.com/a/37965143/6498617.

I prefer that as using highest-basedir didn't work for me with a multi-module project, with nested multi-module poms. The directory-of goal lets you set a property to the path of any module in the whole project, including the root of course. It is also way better than ${session.executionRootDirectory}, because it always works, regardless of whether you build the root or a sub-module, and irrespective of the current working directory where you mvn from.

Solution 6 - Maven

The following small profile worked for me. I needed such a configuration for CheckStyle, which I put into the config directory in the root of the project, so I can run it from the main module and from submodules.

<profile>
    <id>root-dir</id>
    <activation>
        <file>
            <exists>${project.basedir}/../../config/checkstyle.xml</exists>
        </file>
    </activation>
    <properties>
        <project.config.path>${project.basedir}/../config</project.config.path>
    </properties>
</profile>

It won't work for nested modules, but I'm sure it can be modified for that using several profiles with different exists's. (I have no idea why there should be "../.." in the verification tag and just ".." in the overriden property itself, but it works only in that way.)

Solution 7 - Maven

Currently, Maven does not provide such the «Root project directory path» property out of the box.
«Root project» means the «topmost» parent project.

Please, refer to the ticket and consider voting for it: [MNG-7038] Introduce public property to point to a root directory of (multi-module) project - ASF JIRA.

Solution 8 - Maven

I encountered similar problem as i needed to copy files between projects. What Maven does is logical because it will keep the pom.xml installed in repository away from hard coded value.

My solution was to put copied dir in a Maven artifact, then employ Ant to extract/copy

Solution 9 - Maven

I'm not aware of a "nice" way to find the root of a multi-module project. But you can maybe improve a bit your current approach.

A first alternative would be to create an additional module directly under the root project, to declare all EARs as dependencies in it and to use dependency:copy-dependencies to copy the dependencies of the module to the to-deploy directory (relatively). Yes the path would still be relative but since the dependency plugin configuration would be centralized, I don't find it that annoying.

A second alternative would be to use the Maven Assembly Plugin instead of the Maven Dependency Plugin to create a distribution using the dir format (this will create a distribution in a directory). This is actually what I would do.

Solution 10 - Maven

Another solution would be to use an ant task to write "rootdir=${basedir}" to a target/root.properties in the root project, and then use the Properties Plugin to read that file back in. I haven't tried it myself, but I guess it should work..?

Solution 11 - Maven

Except use absolutely root path, in some case, I have another way to solve the problem.

Use maven plugin combine.children feature, refs: maven plugin

I can write my code:

parent pom:

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-dependency-plugin</artifactId>
      <executions>
          <execution>
              <id>copy-dependencies</id>
              <phase>package</phase>
              <goals>
                  <goal>copy-dependencies</goal>
              </goals>
              <configuration>
                  <includeScope>runtime</includeScope>
                  <outputDirectory combine.children="override">${project.basedir}/to-deploy</outputDirectory>
              </configuration>
          </execution>
      </executions>
    </plugin>
  </plugins>
</build>

or write in plugin management, if parent pom doesn't use this plugin.

child pom:

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-dependency-plugin</artifactId>
      <executions>
          <execution>
              <!--same as parent plugin id-->
              <id>copy-dependencies</id>
              <configuration>
                  <outputDirectory combine.children="override">${project.parent.basedir}/to-deploy</outputDirectory>
              </configuration>
          </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Similar way grandchild pom:

<outputDirectory combine.children="override">${project.parent.parent.basedir}/to-deploy</outputDirectory>

Solution 12 - Maven

so that: somewhere in properties of some parent Project I've the file which i need to relate later, what's why i need absolute path on it everywhere. So, i get it with help of groovy:

<properties>	
<source> import java.io.File; 
        String p =project.properties['env-properties-file']; 
        File f = new File(p); 
        if (!f.exists()) 
        { 
           f = new File("../" + p); 
          if (!f.exists()) 
          { 
             f = new File("../../" + p); 
          } 
        } 
        // setting path together with file name in variable xyz_format 
        project.properties['xyz_format'] =f.getAbsolutePath() 
                            + File.separator 
                            + "abc_format.xml"; 
</source>
</properties>

and then:

  <properties>
	 <snapshots>http://localhost:8081/snapshots<snapshots>
	 <releases>http://localhost:8081/releases</releases>
	 <sonar>jdbc:oracle:thin:sonar/sonar@localhost/XE</sonar>
	 <sonar.jdbc.username>sonar</sonar.jdbc.username>
	 <format.conf> ${xyz_format}</format.conf>  <---- here is it!
    </properties>

it works!

Solution 13 - Maven

You can go with something like this. Note, that you have to define two profiles - one which will be activated for the root directory and one for children. Obviously this assumes children will have the same structure but this can be easily adapted.

    <profiles>
        <profile>
            <id>root-dir</id>
            <activation>
                <file>
                    <exists>${basedir}/lib</exists>
                </file>
            </activation>
            <properties>
                <project.libdir>${basedir}/lib</project.libdir>
            </properties>
        </profile>
        <profile>
            <id>child-dir</id>
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
            <properties>
                <project.libdir>${basedir}/../../lib</project.libdir>
            </properties>
        </profile>
    </profiles>

Solution 14 - Maven

With Maven 3.6.1, from a child project, ${parent.basedir} returns the fully qualified directory of the parent project.

Solution 15 - Maven

I've got root directory for parent pom with ${project.parent.basedir}.

Content Type	Original Author	Original Content on Stackoverflow
Question	Christoffer Hammarström	View Question on Stackoverflow
Solution 1 - Maven	anonymous	View Answer on Stackoverflow
Solution 2 - Maven	Grégory Joseph	View Answer on Stackoverflow
Solution 3 - Maven	Karel Vervaeke	View Answer on Stackoverflow
Solution 4 - Maven	Andrejs	View Answer on Stackoverflow
Solution 5 - Maven	sparkyd	View Answer on Stackoverflow
Solution 6 - Maven	Vic	View Answer on Stackoverflow
Solution 7 - Maven	Sergey Vyacheslavovich Brunov	View Answer on Stackoverflow
Solution 8 - Maven	Hoang TO	View Answer on Stackoverflow
Solution 9 - Maven	Pascal Thivent	View Answer on Stackoverflow
Solution 10 - Maven	neu242	View Answer on Stackoverflow
Solution 11 - Maven	markhuang1994	View Answer on Stackoverflow
Solution 12 - Maven	Iakov Senatov	View Answer on Stackoverflow
Solution 13 - Maven	kboom	View Answer on Stackoverflow
Solution 14 - Maven	devdanke	View Answer on Stackoverflow
Solution 15 - Maven	Vlad Cheremisin	View Answer on Stackoverflow

Finding the root directory of a multi module Maven reactor project

Maven Problem Overview

Maven Solutions

Solution 1 - Maven

use `${session.executionRootDirectory}`

Solution 2 - Maven

Solution 3 - Maven

Solution 4 - Maven

Solution 5 - Maven

Solution 6 - Maven

Solution 7 - Maven

Solution 8 - Maven

Solution 9 - Maven

Solution 10 - Maven

Solution 11 - Maven

Solution 12 - Maven

Solution 13 - Maven

Solution 14 - Maven

Solution 15 - Maven

Where does Git store files?

Is the C99 preprocessor Turing complete?

Attributions

Maven Problem Overview

Maven Solutions

Solution 1 - Maven

use ${session.executionRootDirectory}

Solution 2 - Maven

Solution 3 - Maven

Solution 4 - Maven

Solution 5 - Maven

Solution 6 - Maven

Solution 7 - Maven

Solution 8 - Maven

Solution 9 - Maven

Solution 10 - Maven

Solution 11 - Maven

Solution 12 - Maven

Solution 13 - Maven

Solution 14 - Maven

Solution 15 - Maven

Where does Git store files?

Is the C99 preprocessor Turing complete?

Attributions

use `${session.executionRootDirectory}`