Java版Flink使用指南——自定义无界流生成器_Java

大纲

新建工程
- 自定义无界流
使用
打包、提交、运行
工程代码

在《java版flink使用指南——从rabbitmq中队列中接入消息流》一文中，我们让外部组件rabbitmq充当了无界流的数据源，使得flink进行了流式处理。在《java版flink使用指南——将消息写入到rabbitmq的队列中》一文中，我们使用了flink自带的数据生成器，生成了有限数据，从而让flink以批处理形式运行了该任务。
本文我们将自定义一个无界流生成器，以方便后续测试。

新建工程

我们新建一个名字叫unboundedstreamgenerator的工程。
archetype：org.apache.flink:flink-quickstart-java
版本：1.19.1
在这里插入图片描述

自定义无界流

新建src/main/java/org/example/generator/unboundedstreamgenerator.java
然后unboundedstreamgenerator实现richsourcefunction接口

public abstract class richsourcefunction<out> extends abstractrichfunction
        implements sourcefunction<out> {

    private static final long serialversionuid = 1l;
}

主要实现sourcefunction接口的run和cancel方法。run方法用来获取获取，cancel方法用于终止任务。

package org.example.generator;

import org.apache.flink.streaming.api.functions.source.richsourcefunction;

public class unboundedstreamgenerator extends richsourcefunction<long> {
    private volatile boolean isrunning = true;

    @override
    public void run(sourcecontext<long> ctx) throws exception {
        long count = 0l;
        while (isrunning) {
            thread.sleep(1000); // simulate delay
            ctx.collect(count++); // emit data
        }
    }

    @override
    public void cancel() {
        isrunning = false;
        system.out.println("unboundedstreamgenerator canceled");
    }
}

在run方法中，我们每隔一秒产生一条数据，且这个数字自增。

使用

我们使用addsource方法，将该无界流生成器添加成数据源。然后将其输出到日志。

/*
 * 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.example;

import org.apache.flink.streaming.api.environment.streamexecutionenvironment;
import org.example.generator.unboundedstreamgenerator;

/**
 * skeleton for a flink datastream job.
 *
 * <p>for a tutorial how to write a flink application, check the
 * tutorials and examples on the <a href="https://flink.apache.org">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').
 */
public class datastreamjob {

	public static void main(string[] args) throws exception {
		// sets up the execution environment, which is the main entry point
		// to building flink applications.
		final streamexecutionenvironment env = streamexecutionenvironment.getexecutionenvironment();
		env.addsource(new unboundedstreamgenerator()).name("custom stream source")
            .setparallelism(1) 
            .print(); // for demonstration, print the stream to stdout

		// execute program, beginning computation.
		env.execute("flink java api skeleton");
	}
}