Although JavaDoc finds errors and these are displayed in the console for that build, the warnings plugin does not show them in its report.
There are five successful builds in the history before I triggerd the job again. Below i will paste some output from the console:
[javadoc] Generating Javadoc
[javadoc] Javadoc execution
[javadoc] Loading source files for package XXX...
[javadoc] Constructing Javadoc information...
[javadoc] Standard Doclet version 1.8.0_45
[javadoc] Building tree for all the packages and classes...
[javadoc] /home/XXX/.jenkins/jobs/SDK/workspace/Commons/src/de/XXX/XXX/commons/JBossDatasourceController.java:12: error: package org.jboss.as.cli does not exist
[javadoc] import org.jboss.as.cli.CommandContext;
[... more Javadoc errors are displayed ...]
[javadoc] 9 errors
Total time: 4 seconds
[... TASKS plugin output ...]
[WARNINGS] Parsing warnings in console log with parser Java Compiler (javac)
[WARNINGS] Parsing warnings in console log with parser JavaDoc Tool
[WARNINGS] Computing warning deltas based on reference build #57
[WARNINGS] Ignore new warnings since this is the first valid build
[WARNINGS] Plug-in Resultat: Erfolgreich - Kein Grenzwert wurde überschritten
As you can see, there are errors but they are either ignored or not found.
As a side note, many other plugins like TASKS, CHECKSTYLE and FINDBUGS also print "Ignore new warnings since this is the first valid build" during the post build process, so maybe the root of this problem is not the warnings plugin?