Java specification version comparison fails for single-number versions
JavaSpecVersion.java is used to compare Java Specification Versions (the result of System.getProperty( "java.specification.version" ) ).
The code expects the version number to have have a major and minor version part, separated by a dot: 1.8.
Java 11 returns only a single value: 11.
As a result, Openfire incorrectly assumes that Java 11 is older than Java 8, which prevents plugins that require Java 8 or newer, from being loaded.