When building https://gerrit.wikimedia.org/r/wmf-jvm-utils with Java 11 I encounter:
```counterexample
[INFO] --- maven-javadoc-plugin:3.2.0:jar (attach-javadocs) @ http-client-utils ---
[ERROR] MavenReportException: Error while generating Javadoc: Unable to find javadoc command: The environment variable JAVA_HOME is not correctly set.
org.apache.maven.reporting.MavenReportException: Unable to find javadoc command: The environment variable JAVA_HOME is not correctly set.
at org.apache.maven.plugins.javadoc.AbstractJavadocMojo.executeReport (AbstractJavadocMojo.java:2019)
...
Caused by: java.io.IOException: The environment variable JAVA_HOME is not correctly set.
```
The reason is Java 9 moved `javadoc` to `JAVA_HOME/bin/javadoc` and the Maven javadoc plugin 3.2.0 does not take that in account. A workaround is to set `javadocExecutable` using Maven profiles varying based on the JDK version has I have done in https://gerrit.wikimedia.org/g/integration/gearman-java
:
```
lang=xml,name=pom.xml
<profiles>
<profile>
<id>jdk-8-config</id>
<activation>
<jdk>1.8</jdk>
</activation>
<properties>
<javadocExecutable>${java.home}/../bin/javadoc</javadocExecutable>
</properties>
</profile>
<profile>
<id>jdk-11-config</id>
<activation>
<jdk>11</jdk>
</activation>
<properties>
<javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
</properties>
</profile>
```
After some digging, that got fixed upstream [[ https://issues.apache.org/jira/browse/MJAVADOC-650 | MJAVADOC-650 ]] / [[ https://github.com/apache/maven-javadoc-plugin/pull/60/files | Pull request 60 ]] which handles the relocation.
The fix has been released in maven-javadoc-plugin 3.3.0.
Both wmf-jvm-utils and integration/gearman-java get it from our parent-pom https://gerrit.wikimedia.org/g/wikimedia/discovery/discovery-parent-pom/+/refs/heads/master which has:
```
lang=xml,name=pom.xml
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>3.2.0</version>
```
It should be upgraded to 3.3.0 and the downstream repositories updated.