From Evgeny Goldin

Introduction

Most of the time POMs operate on files located somewhere relative to ${project.basedir}:

• ${project.basedir}/src/main/java
• ${project.basedir}/src/main/scripts
• ${project.basedir}/../otherModule

Sometimes, file or directory path can not be expressed as a function of ${project.basedir}. It happens if some plugin is configured in aggregator/parent POM and needs an access to a certain directory. This "special" directory may contain a script to run or a data file to use. Since ${project.basedir}-related expressions are evaluated in the context of currently executing POM we can't use them in aggregator/parent POM: something that is "${project.basedir}/../../specialDir" in one child module, can be "${project.basedir}/../specialDir" or "${project.basedir}/specialDir" in another.

We need a way to get an absolute, not relative path:

<plugin>
    <groupId>com.github.goldin</groupId>
    <artifactId>find-maven-plugin</artifactId>
    <version>0.2.5</version>
    <executions>
        <execution>
            <id>find-special-dir</id>
            <goals>
                <goal>find</goal>
            </goals>
            <phase>validate</phase>
            <configuration>
                <runIf>{{ .. }}</runIf>
                <propertyName>special.dir.path</propertyName>
                <sysPropertyName>special.dir.path</sysPropertyName>
                <file>SPECIAL_DIR</file>
                <!-- Default value -->
                <startDir>${project.basedir}</startDir>
                <!-- Default value -->
                <failIfNotFound>true</failIfNotFound>
            </configuration>
        </execution>
    </executions>
</plugin>

• <runIf> is optional. It specifies if plugin needs to be run, see "copy-maven-plugin" documentation for more details.
• "find-maven-plugin" "climbs up" directories starting from the <startDir> and looking for "SPECIAL_DIR" directory. It goes up until it either finds the "SPECIAL_DIR" or gets to the top and fails, if <failIfNotFound> is "true".
• When found, Maven property ${special.dir.path} is set to directory's canonical path.
• If <sysPropertyName> is specified, system property with name specified is set as well.
• If executed again in the same build, "find-maven-plugin" does nothing since all variables are already set, so the "climbing" process only happens once.

Files can be searched for as well:

<plugin>
    <groupId>com.github.goldin</groupId>
    <artifactId>find-maven-plugin</artifactId>
    <version>0.2.5</version>
    <executions>
        <execution>
            <id>find-about-file</id>
            <goals>
                <goal>find</goal>
            </goals>
            <phase>validate</phase>
            <configuration>
                <propertyName>about.file.path</propertyName>
                <file>src/main/scripts/about.xml</file>
            </configuration>
        </execution>
    </executions>
</plugin>

Now, having ${special.dir.path} and ${about.file.path} properties set we can use them for any purpose, as a usual Maven property. This time it is not ${project.basedir}-related expression and always contains the same full path of directory or file found in any child POM, regardless of its depth.

Details