@Override
    public UserPageAdClick apply(PageView pv, AdClick ac) {
      return new UserPageAdClick(pv.getUserId(), pv.getPageId(), ac.getAdId());
    }
A {@link StreamApplication} that demonstrates a partitionBy, stream-stream join and a windowed count.
samza-test/src/test/java/org/apache/samza/test/operator/RepartitionJoinWindowApp.java