@Override public boolean matches(ConditionContext context, AnnotatedTypeMetadata a) {
      return !isEmpty(
        context.getEnvironment().getProperty("zipkin.collector.activemq.url")) &&
        notFalse(context.getEnvironment().getProperty("zipkin.collector.activemq.enabled"));
    }
This condition passes when {@link ZipkinActiveMQCollectorProperties#getUrl()}} is set to
non-empty.

<p>This is here because the yaml defaults this property to empty like this, and spring-boot
doesn't have an option to treat empty properties as unset.

<pre>{@code
url: ${ACTIVEMQ_URL:}
}</pre>
zipkin-server/src/main/java/zipkin2/server/internal/activemq/ZipkinActiveMQCollectorConfiguration.java