Java tutorial
/* * 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 * * 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.streams.rss.provider; import org.apache.streams.config.ComponentConfigurator; import org.apache.streams.config.StreamsConfiguration; import org.apache.streams.config.StreamsConfigurator; import org.apache.streams.core.StreamsDatum; import org.apache.streams.core.StreamsProvider; import org.apache.streams.core.StreamsResultSet; import org.apache.streams.jackson.StreamsJacksonMapper; import org.apache.streams.rss.RssStreamConfiguration; import org.apache.streams.rss.provider.perpetual.RssFeedScheduler; import org.apache.streams.util.ComponentUtils; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.google.common.annotations.VisibleForTesting; import com.google.common.base.Preconditions; import com.google.common.util.concurrent.Uninterruptibles; import com.typesafe.config.Config; import com.typesafe.config.ConfigFactory; import com.typesafe.config.ConfigParseOptions; import org.joda.time.DateTime; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.PrintStream; import java.math.BigInteger; import java.util.Queue; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ConcurrentLinkedQueue; import java.util.concurrent.ExecutorService; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicBoolean; /** * RSS {@link org.apache.streams.core.StreamsProvider} that provides content from rss feeds in boilerpipe format */ public class RssStreamProvider implements StreamsProvider { private static final String STREAMS_ID = "RssStreamProvider"; private static final Logger LOGGER = LoggerFactory.getLogger(RssStreamProvider.class); private static final int MAX_SIZE = 1000; private RssStreamConfiguration config; private boolean perpetual; private ExecutorService executor; private BlockingQueue<StreamsDatum> dataQueue; private AtomicBoolean isComplete; @VisibleForTesting protected RssFeedScheduler scheduler; public RssStreamProvider() { this(new ComponentConfigurator<>(RssStreamConfiguration.class) .detectConfiguration(StreamsConfigurator.getConfig().getConfig("rss")), false); } public RssStreamProvider(boolean perpetual) { this(new ComponentConfigurator<>(RssStreamConfiguration.class) .detectConfiguration(StreamsConfigurator.getConfig().getConfig("rss")), perpetual); } public RssStreamProvider(RssStreamConfiguration config) { this(config, false); } public RssStreamProvider(RssStreamConfiguration config, boolean perpetual) { this.perpetual = perpetual; this.config = config; } @Override public String getId() { return STREAMS_ID; } @Override public void startStream() { LOGGER.trace("Starting Rss Scheduler"); this.executor.submit(this.scheduler); } @Override public StreamsResultSet readCurrent() { Queue<StreamsDatum> batch = new ConcurrentLinkedQueue<>(); int batchSize = 0; while (!this.dataQueue.isEmpty() && batchSize < MAX_SIZE) { StreamsDatum datum = ComponentUtils.pollWhileNotEmpty(this.dataQueue); if (datum != null) { ++batchSize; batch.add(datum); } } this.isComplete.set(this.scheduler.isComplete() && batch.isEmpty() && this.dataQueue.isEmpty()); return new StreamsResultSet(batch); } @Override public StreamsResultSet readNew(BigInteger sequence) { return null; } @Override public StreamsResultSet readRange(DateTime start, DateTime end) { return null; } @Override public boolean isRunning() { return !this.isComplete.get(); } @Override public void prepare(Object configurationObject) { this.executor = new ThreadPoolExecutor(1, 4, 15L, TimeUnit.SECONDS, new LinkedBlockingQueue<>()); this.dataQueue = new LinkedBlockingQueue<>(); this.scheduler = getScheduler(this.dataQueue); this.isComplete = new AtomicBoolean(false); int consecutiveEmptyReads = 0; } @VisibleForTesting protected RssFeedScheduler getScheduler(BlockingQueue<StreamsDatum> queue) { if (this.perpetual) { return new RssFeedScheduler(this.executor, this.config.getFeeds(), queue); } else { return new RssFeedScheduler(this.executor, this.config.getFeeds(), queue, 0); } } @Override public void cleanUp() { this.scheduler.stop(); ComponentUtils.shutdownExecutor(this.executor, 10, 10); } /** * To use from command line: * * <p/> * Supply configuration similar to src/test/resources/rss.conf * * <p/> * Launch using: * * <p/> * mvn exec:java -Dexec.mainClass=org.apache.streams.rss.provider.RssStreamProvider -Dexec.args="rss.conf articles.json" * @param args args * @throws Exception Exception */ public static void main(String[] args) throws Exception { Preconditions.checkArgument(args.length >= 2); String configfile = args[0]; String outfile = args[1]; Config reference = ConfigFactory.load(); File file = new File(configfile); assert (file.exists()); Config testResourceConfig = ConfigFactory.parseFileAnySyntax(file, ConfigParseOptions.defaults().setAllowMissing(false)); Config typesafe = testResourceConfig.withFallback(reference).resolve(); StreamsConfiguration streamsConfiguration = StreamsConfigurator.detectConfiguration(typesafe); RssStreamConfiguration config = new ComponentConfigurator<>(RssStreamConfiguration.class) .detectConfiguration(typesafe, "rss"); RssStreamProvider provider = new RssStreamProvider(config); ObjectMapper mapper = StreamsJacksonMapper.getInstance(); PrintStream outStream = new PrintStream(new BufferedOutputStream(new FileOutputStream(outfile))); provider.prepare(config); provider.startStream(); do { Uninterruptibles.sleepUninterruptibly(streamsConfiguration.getBatchFrequencyMs(), TimeUnit.MILLISECONDS); for (StreamsDatum datum : provider.readCurrent()) { String json; try { json = mapper.writeValueAsString(datum.getDocument()); outStream.println(json); } catch (JsonProcessingException ex) { System.err.println(ex.getMessage()); } } } while (provider.isRunning()); provider.cleanUp(); outStream.flush(); } }