| /* |
| Licensed to the Apache Software Foundation (ASF) under one |
| or more contributor license agreements. See the NOTICE file |
| distributed with this work for additional information |
| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, |
| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| KIND, either express or implied. See the License for the |
| specific language governing permissions and limitations |
| under the License. |
| */ |
| |
| package org.apache.edgent.samples.topology; |
| |
| import java.util.Random; |
| import java.util.concurrent.TimeUnit; |
| |
| import org.apache.edgent.providers.direct.DirectProvider; |
| import org.apache.edgent.topology.TStream; |
| import org.apache.edgent.topology.Topology; |
| |
| /** |
| * Periodic polling of source data. |
| * |
| */ |
| public class PeriodicSource { |
| /** |
| * Shows polling a data source to periodically obtain a value. |
| * Polls a random number generator for a new value every second |
| * and then prints out the raw value and a filtered and transformed stream. |
| * @param args command arguments |
| * @throws Exception on failure |
| */ |
| public static void main(String[] args) throws Exception { |
| |
| DirectProvider tp = new DirectProvider(); |
| |
| Topology t = tp.newTopology("PeriodicSource"); |
| |
| // Since this is the Direct provider the graph can access |
| // objects created while the topology is being defined |
| // (in this case the Random object r). |
| Random r = new Random(); |
| TStream<Double> gaussian = t.poll(() -> r.nextGaussian(), 1, TimeUnit.SECONDS); |
| |
| // Peek at the value on the Stream printing it to System.out |
| gaussian = gaussian.peek(g -> System.out.println("R:" + g)); |
| |
| // A filter |
| gaussian = gaussian.filter(g -> g > 0.5); |
| |
| // A transformation |
| TStream<String> gs = gaussian.map(g -> "G:" + g + ":"); |
| gs.print(); |
| |
| tp.submit(t); |
| } |
| } |