Maven exec:java goal on a multi-module project

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.

Answer 2

• You should bind the exec-maven-plugin to a maven lifecycle goal, say verify.
• Since you want the plugin to be executed only for module2, define the plugin configurations in the parent pom within pluginManagement. Use the same only in module 2.
• Then run the following:

mvn verify -Dexec.mainClass=MyMain.

parent pom

<build>     <pluginManagement>         <plugins>             <plugin>                 <groupId>org.codehaus.mojo</groupId>                 <artifactId>exec-maven-plugin</artifactId>                 <version>1.2.1</version>                 <executions>                  <execution>                      <phase>verify</phase>                      <goals>                          <goal>java</goal>                      </goals>                  </execution>                 </executions>             </plugin>         </plugins>     </pluginManagement> </build> 

module 2

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