How to force a javadoc jar even though there is no (public) Javadoc?

Question

I have a Maven multi module project of which some of the sub modules are only for internal use. I don't wish to publish any visible Javadoc for it, as it should not be used directly by 3rd parties. There is not a single public package in them (the package name itself has something like a.b.c.internal.d).

However, to release a jar to Maven Central, OSS Sonatype requires that all library jars have accompanying sources and javadoc jars.

How can I force a javadoc jar to be created with a fixed index or so that tells the purpose of the sub module? A package-info.java comes to mind, but I have no public packages (all packages with the word "internal" in it are ignored).

Answer 1

Don't use the Javadoc tool to produce a jar with non-standard content: use maven-jar-plugin instead to manually create one.

Initial solution taken from https://vzurczak.wordpress.com/2014/08/01/generate-an-empty-javadoc-jar-file/

Here's the final solution I settled on and works generically for all submodules when configured in the parent pom:

Define two profiles:

• one to execute the standard javadoc plugin if no custom javadoc folder is present in the submodule (src/main/javadoc is missing)
• one to execute custom javadoc by means of jar plugin if a custom javadoc folder is present in the submodule (src/main/javadoc is present)

Maven config:

<profiles>
    <profile>
        <id>standard-javadoc</id>
        <activation>
            <file><missing>src/main/javadoc</missing></file>
        </activation>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-javadoc-plugin</artifactId>
                    <executions>
                        <execution>
                            <id>attach-javadocs</id>
                            <goals>
                                <goal>jar</goal>
                            </goals>
                            <phase>package</phase>
                            <configuration>
                                <show>public</show>
                                <failOnError>false</failOnError>
                                <detectOfflineLinks>false</detectOfflineLinks>
                                <doclint>all,-missing</doclint>
                                <nohelp>true</nohelp>
                                <excludePackageNames>*.internal.*,testutil,demo</excludePackageNames>
                                <quiet>true</quiet>
                            </configuration>
                        </execution>
                    </executions>
                    <configuration>
                        <failOnError>false</failOnError>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </profile>

    <profile>
        <id>custom-javadoc</id>
        <activation>
            <file><exists>src/main/javadoc</exists></file>
        </activation>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-jar-plugin</artifactId>
                    <executions>
                        <execution>
                            <phase>package</phase>
                            <goals>
                                <goal>jar</goal>
                            </goals>
                            <configuration>
                                <classifier>javadoc</classifier>
                                <classesDirectory>${project.basedir}/src/main/javadoc</classesDirectory>
                            </configuration>
                        </execution>
                    </executions>
                </plugin>
            </plugins>
        </build>
    </profile>
</profiles>