Maven variable for reactor root

Question

In a multi-module maven project, is there a variable that points to the root project folder?

• ${project.basedir} points to the current project's directory,
• ${project.parent.basedir} points to the parent project's directory,

but is there a variable that always points to the root directory (the one from which the maven command was executed), no matter from which project inside the reactor?

---

I realized that the problem I wanted to solve is pretty much unsolvable. I wanted a variable that pointed to either project.basedir, project.parent.basedir, project.parent.parent.basedir etc, whichever is higher. But since a project's parent pom need not be it's parent in the file system, my whole approach won't help. So I am accepting Pascal's answer because it answers my question (even if my question does not solve my problem).

Answer 1

Use directory-maven-plugin with directory-of goal.

Unlike other suggestions:

• This solution works for multi-module projects.
• It works whether you build the whole project or a sub-module
• It works whether you run maven from the root folder or a sub-module (unlike ${session.executionRootDirectory}
• There's no need to set a relative path property in each and every sub-module!

The plugin lets you set a property of your choice to the absolute-path of any of the project's modules. In my case I set it to the root module... In my project root pom:

 <plugin>
                <groupId>org.commonjava.maven.plugins</groupId>
                <artifactId>directory-maven-plugin</artifactId>
                <version>0.1</version>
                <executions>
                    <execution>
                        <id>directories</id>
                        <goals>
                            <goal>directory-of</goal>
                        </goals>
                        <phase>initialize</phase>
                        <configuration>
                            <property>myproject.basedir</property>
                            <project>
                                <groupId>com.my.domain</groupId>
                                <artifactId>my-root-artifact</artifactId>
                            </project>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

From then on, ${myproject.basedir} in any sub-module pom always has the path of the project root module. And of course, you can set the property to any module, not just the root...

Answer 2

For me, there was a need for root directory during variable interpolation, not for plugins section - for local directory relative to root with hand-crafted jars. I know this is a bad practice to have local directory with jars, but this was a requirement of project.

Why I was unable to use different solutions:

• ${session.executionRootDirectory} and ${user.dir} are tied with directory from which maven command was executed. I want to refer to the same directory independently of directory, from which maven was launched.
• ${project.basedir} ,as mentioned above, points to current project directory, so child modules will search for jars in wrong location.
• I had about 100 projects, so defining relative paths or usage of accepted answer for this question is quite complex in my case.
• Directory plugin can be used only for plugin configurations, not for variable interpolation

So, in my case with bad requirements I have used environment variable which refers project root and used it in pom.xml. Use it as last resort, when other solutions do not work. Here is example, how I use environment variable in my case:

<repositories>
    <repository>
        <id>local-maven-repo</id>
        <!--NOTE: export PROJECT_ROOT=<location>-->
        <url>file:///${env.PROJECT_ROOT}/local-repo</url>
    </repository>
</repositories>

Answer 3

In Maven 3, ${session.executionRootDirectory} is "a variable that always points to the ... directory ... from which the maven command was executed."

Note that this is distinct from a property that gives the top-level root directory of a multi-module project, regardless of where in the directory structure mvn is executed from. Such a property does not exist to my knowledge, but you can use the ${basedir}/.. hack to achieve it. See this thread on maven-users for more details.

See also: Finding the root directory of a multi module maven reactor project

Answer 4

Such property can be created using: directory-maven-plugin. Using the plugin's highest-basedir goal you can assign the root path to any property you specify.

Answer 5

is there a variable that always points to the root directory (the one from which the maven command was executed)

user.dir (the working directory) should be that directory.

Answer 6

In the latest maven, you can use ${maven.multiModuleProjectDirectory}.