I have a maven project with a parent module and 6 sub-modules. 3 of them are applications and the rest are the common modules that the 3 apps depend on.

The parent module only has a pom.xml without any code. I’m trying to use proguard to obfuscate all the 6 modules. The proguard maven plugin is defined in the parent pom.

The issue is when I run mvn package, I got error

 [proguard] java.io.IOException: The input is empty. You have to specify one or more '-injars' options.

I think it’s because the parent module doesn’t have any code (thus no class files or jars) so it cannot find a input jar. My proguard config is as below:

        <plugin>
            <groupId>com.github.wvengen</groupId>
            <artifactId>proguard-maven-plugin</artifactId>
            <version>2.6.1</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>proguard</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <injar>${project.build.finalName}.jar</injar>
                <outjar>${project.build.finalName}-small.jar</outjar>
                <obfuscate>true</obfuscate>
                <proguardInclude>${project.basedir}/../proguard.cfg</proguardInclude>
                <libs>
                    <lib>${java.home}/jmods/java.base.jmod</lib>
                    <lib>${java.home}/jmods/java.management.jmod</lib>
                    <lib>${java.home}/jmods/jdk.management.jmod</lib>
                    <lib>${java.home}/jmods/java.sql.jmod</lib>
                    <lib>${java.home}/jmods/java.xml.jmod</lib>
                </libs>
                <outputDirectory>${project.basedir}/target</outputDirectory>
            </configuration>
        </plugin>

I also tried to run it in a child module and it succeeded. So I guess it just couldn’t find a ${project.build.finalName}.jar in the parent module.

I wonder if I can fix it by:

• Tweak some configs in proguard OR
• use another obfuscation plugin if proguard doesn’t support my case OR
• Do not run the plugin in parent module, only run it in the child modules. (not sure if possible?)