public final T walk(T context, JobNode jn) {
		if (jn instanceof Flow) {
			return walk(context, (Flow) jn);
		}
		else if (jn instanceof JobDefinition) {
			return walk(context, (JobDefinition) jn);
		}
		else if (jn instanceof JobReference) {
			return walk(context, (JobReference) jn);
		}
		else if (jn instanceof Split) {
			return walk(context, (Split) jn);
		}
		else {
			throw new IllegalStateException("nyi:" + jn.getClass().getName());
		}
	}
Called to start a visit of a specific JobSpec.
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/job/dsl/JobSpecificationVisitor.java