Maven variable for reactor root

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 开发者_JAVA技巧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).

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.

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

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

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...

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.

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>

As far I think, there is no such variable. There are only workaround like in accepted answer of Maven2 property that indicates the parent directory .