Flink入门程序

Flink的WordCount

使用idea创建一个flink的模板项目：

使用该模板创建项目时，需要安装Scala插件（这个烦请自己找资源）。

准备工作做好之后，就可以操作了。当模板项目创建好之后，发现有2个模板类，一个是流式处理，一个是批量处理。

这里我将代码写进去进行执行：

下面这是批量处理的类。

/*
 * 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.feng;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.operators.AggregateOperator;
import org.apache.flink.api.java.operators.DataSource;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.util.Collector;


import java.util.Collection;

/**
 * Skeleton for a Flink Batch Job.
 *
 * <p>For a tutorial how to write a Flink batch application, check the
 * tutorials and examples on the <a href="http://flink.apache.org/docs/stable/">Flink Website</a>.
 *
 * <p>To package your application into a JAR file for execution,
 * change the main class in the POM.xml file to this class (simply search for 'mainClass')
 * and run 'mvn clean package' on the command line.
 * @author Feng
 */
public class BatchJob {

	public static void main(String[] args) throws Exception {
		// set up the batch execution environment
		final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

		DataSource<String> dataSource = env.readTextFile("D:\\jee-2019-7-idea-maven-workspace\\flink\\target\\classes" +
				"\\txt\\wordcount.txt", "UTF-8");

		dataSource.flatMap(new WordFlatFunction())
				.groupBy(0)
				.sum(1)
				.print();
	}

	private static class WordFlatFunction implements FlatMapFunction<String, Tuple2<String, Integer>>{
		private static final long serialVersionUID = -868609327661485759L;
		private String space = " ";

		@Override
		public void flatMap(String words, Collector<Tuple2<String, Integer>> collector) throws Exception {
			for (String word : words.toLowerCase().split(space)) {
				collector.collect(new Tuple2<>(word, 1));
			}
		}
	}
}

执行代码时，若出现类加载不到，就查看下面图中的这个位置（我的这个状态是可以执行的）：

这是因为依赖的Scope的问题，创建好的项目是将运provide。不会在运行时打包的。

然后是运行流处理的那个类：

/*
 * 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.feng;

import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.util.Collector;


/**
 * Skeleton for a Flink Streaming Job.
 *
 * <p>For a tutorial how to write a Flink streaming application, check the
 * tutorials and examples on the <a href="http://flink.apache.org/docs/stable/">Flink Website</a>.
 *
 * <p>To package your application into a JAR file for execution, run
 * 'mvn clean package' on the command line.
 *
 * <p>If you change the name of the main class (with the public static void main(String[] args))
 * method, change the respective entry in the POM.xml file (simply search for 'mainClass').
 * @author Feng
 */
public class StreamingJob {

	public static void main(String[] args) throws Exception {
		/// nc -l -p 12345 监听12345端口
		// set up the streaming execution environment
		final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
		DataStream<String> dataStream = env.socketTextStream("localhost", 12345);

		String regx = "\\W+";
		DataStream<Tuple2<String, Integer>> dataStream1 = dataStream
			.flatMap((String words, Collector<Tuple2<String, Integer>> collector)->{
				for (String word : words.toLowerCase().split(regx)) {
					collector.collect(new Tuple2<>(word, 1));
				}
			}).returns(Types.TUPLE(Types.STRING, Types.INT));

		// 对Tuple的第一个字段分组
		dataStream1.keyBy(0)
			.timeWindowAll(Time.seconds(1))
			// 对Tuple的第二个字段求和
			.sum(1)
			.print()
			.setParallelism(1);

		env.execute("Flink Streaming Java API Skeleton");
	}
}

流处理的这个程序是监听一个本地的端口，使用netcat往该端口上发送数据即可监听到。在本地运行时，需要安装netcat的windows版本（https://eternallybored.org/misc/netcat/）。点击这里的连接，下载1.1.2版本。之后解压该压缩包，将里边的所有子文件复制到System32文件夹下，就可以用cmd去访问了。命令是nc -l -p [port]，我这里监听的是12345端口。注意程序的启动顺序，打开cmd的窗口，输入命令，再去启动你的flink程序。整个过程不需要任何Flink环境（不用下载Flink压缩包）。