Question

I’m trying to run exec-maven-plugin‘s exec:java goal on a simple two-module project where one module depends on the other. So far I can’t find a configuration that works. Here’s a boiled-down test case:

+ exec-multi-module-test/
    + pom.xml
    + module1/
        + pom.xml
        + src/
            + main/
                + java/
                    + HelloPrinter.java
    + module2/
        + pom.xml
        + src/
            + main/
                + java/
                    + MyMain.java

Here’s the parent pom:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mkscrg.sandbox</groupId>
    <artifactId>exec-multi-module-test</artifactId>
    <version>1.0</version>
    <packaging>pom</packaging>

    <modules>
        <module>module1</module>
        <module>module2</module>
    </modules>

    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.2.1</version>
            </plugin>
        </plugins>
    </build>
</project>

module1‘s pom:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <artifactId>exec-multi-module-test</artifactId>
        <groupId>com.mkscrg.sandbox</groupId>
        <version>1.0</version>
    </parent>

    <artifactId>module1</artifactId>
</project>

module2‘s pom:

4.0.0

    <parent>
        <artifactId>exec-multi-module-test</artifactId>
        <groupId>com.mkscrg.sandbox</groupId>
        <version>1.0</version>
    </parent>

    <artifactId>module2</artifactId>

    <dependencies>
        <dependency>
            <groupId>com.mkscrg.sandbox</groupId>
            <artifactId>module1</artifactId>
            <version>${project.version}</version>
        </dependency>
    </dependencies>
</project>

This project compiles successfully from the top, but running mvn exec:java -Dexec.mainClass=myMain fails:

[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] exec-multi-module-test
[INFO] module1
[INFO] module2
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building exec-multi-module-test 1.0
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ exec-multi-module-test >>>
[INFO] 
[INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ exec-multi-module-test <<<
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ exec-multi-module-test ---
[WARNING] 
java.lang.ClassNotFoundException: MyMain
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:285)
        at java.lang.Thread.run(Thread.java:680)
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] exec-multi-module-test ............................ FAILURE [0.363s]
[INFO] module1 ........................................... SKIPPED
[INFO] module2 ........................................... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.566s
[INFO] Finished at: Mon Jun 18 14:11:54 PDT 2012
[INFO] Final Memory: 3M/81M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project exec-multi-module-test: An exception occured while executing the Java class. MyMain -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

What’s the right way to configure this project to allow exec:java to see MyMain?

EDIT: Here’s a gist if you’d like to try this yourself: https://gist.github.com/2950830

EDIT: Clarification: I know it’s possible to mvn install and then either run exec:java from module2‘s directory or use the -pl flag from the top. However, I’d like to avoid running mvn install. It shouldn’t be necessary to modify my local repository in order to run this goal in a multi-module project. Just as mvn compile "just works" with a multi-module project, so should other goals/phases.

Answer 1

Goals in a multi-module project, when run from the parent, will run against all modules. I don’t think that’s what you want. You can try:

mvn exec:java -pl module2 -Dexec.mainClass=MyMain

That might work? More info:

• Running a specific Maven plugin goal from the command line in a sub-module of a multi-module reactor project

However, I think it’s more intuitive to change directory to the sub-module containing the executable before running it.