Pattern API

Apache Flink provides a pattern API to apply complex event processing on the data stream. Some important methods are:

• begin: This defines the pattern starting state and can be written as follows:

Pattern<Event, ?> start = Pattern.<Event>begin("start");

• followedBy: This appends a new pattern state but here other events can occur between two matching events as follows:

Pattern<Event, ?> followedBy = start.followedBy("next");

• where: This defines a filter condition for the current pattern state and, if the event passes the filter, it can match the state as follows:

patternState.where(new FilterFunction <Event>() {
@Override
    public boolean filter(Event value) throws Exception {
        return ... // some condition
    }
});

• within: This defines the maximum time interval for an event sequence to match the pattern post that is discarded. It's written as follows:

patternState.within(Time.seconds(10));

• subtype(subClass): This defines a subtype condition for the current...