[Tm4j-developers] bug in TopicMapWalker

[Conal T. <Con...@vu...>]

We're writing a new back end which supports only "static merging" and
this caused us to discover a bug in TM4J.

On line 85 of org.tm4j.topicmap.util.TopicMapWalker it assumes that a
Topic must have a non-null "base topic", though the javadoc for
Topic.getBaseTopic() says that it may return null if a topic has no
"base topic".

Because our back end uses static (eager) merging, we don't have "base
topics" at all, so we had an Topic implementation like this:

	public Topic getBaseTopic() {
		// doesn't support dynamic merging so this doesn't apply
		return null;
	}

BTW to keep TopicMapWalker happy I've since changed it to:

	public Topic getBaseTopic() {
		// doesn't support dynamic merging so this doesn't apply
		return this;
	}

Cheers

Con