Flink（六）Flink自定义Data Sink

傷城~ 2022-02-19 04:19 265阅读 0赞

## 前言 ##

这篇文章将写一个 demo 教大家将从 Kafka Source 的数据 Sink 到 MySQL 中去。

## 准备工作 ##

我们先来看下 Flink 从 Kafka topic 中获取数据的 demo，首先你需要安装好了 Flink 和 Kafka 。

运行启动 Flink、Zookepeer、Kafka

![Image 1][]

好了，都启动了！

## 数据库建表 ##

DROP TABLE IF EXISTS `student`;
    CREATE TABLE `student` (
      `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
      `name` varchar(25) COLLATE utf8_bin DEFAULT NULL,
      `password` varchar(25) COLLATE utf8_bin DEFAULT NULL,
      `age` int(10) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

## 实体类 ##

Student.java

package com.zhisheng.flink.model;
    
    /**
     * Desc:
     * weixin: zhisheng_tian
     * blog: http://www.54tianzhisheng.cn/
     */
    public class Student {
        public int id;
        public String name;
        public String password;
        public int age;
    
        public Student() {
        }
    
        public Student(int id, String name, String password, int age) {
            this.id = id;
            this.name = name;
            this.password = password;
            this.age = age;
        }
    
        @Override
        public String toString() {
            return "Student{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", password='" + password + '\'' +
                    ", age=" + age +
                    '}';
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    }

## 工具类 ##

工具类往 kafka topic student 发送数据

import com.alibaba.fastjson.JSON;
    import com.zhisheng.flink.model.Metric;
    import com.zhisheng.flink.model.Student;
    import org.apache.kafka.clients.producer.KafkaProducer;
    import org.apache.kafka.clients.producer.ProducerRecord;
    
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Properties;
    
    /**
     * 往kafka中写数据
     * 可以使用这个main函数进行测试一下
     * weixin: zhisheng_tian
     * blog: http://www.54tianzhisheng.cn/
     */
    public class KafkaUtils2 {
        public static final String broker_list = "localhost:9092";
        public static final String topic = "student";  //kafka topic 需要和 flink 程序用同一个 topic
    
        public static void writeToKafka() throws InterruptedException {
            Properties props = new Properties();
            props.put("bootstrap.servers", broker_list);
            props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
            props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
            KafkaProducer producer = new KafkaProducer<String, String>(props);
    
            for (int i = 1; i <= 100; i++) {
                Student student = new Student(i, "zhisheng" + i, "password" + i, 18 + i);
                ProducerRecord record = new ProducerRecord<String, String>(topic, null, null, JSON.toJSONString(student));
                producer.send(record);
                System.out.println("发送数据: " + JSON.toJSONString(student));
            }
            producer.flush();
        }
    
        public static void main(String[] args) throws InterruptedException {
            writeToKafka();
        }
    }

## SinkToMySQL ##

该类就是 Sink Function，继承了 RichSinkFunction ，然后重写了里面的方法。在 invoke 方法中将数据插入到 MySQL 中。

package com.zhisheng.flink.sink;
    
    import com.zhisheng.flink.model.Student;
    import org.apache.flink.configuration.Configuration;
    import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    
    /**
     * Desc:
     * weixin: zhisheng_tian
     * blog: http://www.54tianzhisheng.cn/
     */
    public class SinkToMySQL extends RichSinkFunction<Student> {
        PreparedStatement ps;
        private Connection connection;
    
        /**
         * open() 方法中建立连接，这样不用每次 invoke 的时候都要建立连接和释放连接
         *
         * @param parameters
         * @throws Exception
         */
        @Override
        public void open(Configuration parameters) throws Exception {
            super.open(parameters);
            connection = getConnection();
            String sql = "insert into Student(id, name, password, age) values(?, ?, ?, ?);";
            ps = this.connection.prepareStatement(sql);
        }
    
        @Override
        public void close() throws Exception {
            super.close();
            //关闭连接和释放资源
            if (connection != null) {
                connection.close();
            }
            if (ps != null) {
                ps.close();
            }
        }
    
        /**
         * 每条数据的插入都要调用一次 invoke() 方法
         *
         * @param value
         * @param context
         * @throws Exception
         */
        @Override
        public void invoke(Student value, Context context) throws Exception {
            //组装数据，执行插入操作
            ps.setInt(1, value.getId());
            ps.setString(2, value.getName());
            ps.setString(3, value.getPassword());
            ps.setInt(4, value.getAge());
            ps.executeUpdate();
        }
    
        private static Connection getConnection() {
            Connection con = null;
            try {
                Class.forName("com.mysql.jdbc.Driver");
                con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8", "root", "root123456");
            } catch (Exception e) {
                System.out.println("-----------mysql get connection has exception , msg = "+ e.getMessage());
            }
            return con;
        }
    }

## Flink 程序 ##

这里的 source 是从 kafka 读取数据的，然后 Flink 从 Kafka 读取到数据（JSON）后用阿里 fastjson 来解析成 student 对象，然后在 addSink 中使用我们创建的 SinkToMySQL，这样就可以把数据存储到 MySQL 了。

package com.zhisheng.flink;
    
    import com.alibaba.fastjson.JSON;
    import com.zhisheng.flink.model.Student;
    import com.zhisheng.flink.sink.SinkToMySQL;
    import org.apache.flink.api.common.serialization.SimpleStringSchema;
    import org.apache.flink.streaming.api.datastream.DataStreamSource;
    import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
    import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
    import org.apache.flink.streaming.api.functions.sink.PrintSinkFunction;
    import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer011;
    import org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011;
    
    import java.util.Properties;
    
    /**
     * Desc:
     * weixin: zhisheng_tian
     * blog: http://www.54tianzhisheng.cn/
     */
    public class Main3 {
        public static void main(String[] args) throws Exception {
            final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
    
            Properties props = new Properties();
            props.put("bootstrap.servers", "localhost:9092");
            props.put("zookeeper.connect", "localhost:2181");
            props.put("group.id", "metric-group");
            props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
            props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
            props.put("auto.offset.reset", "latest");
    
            SingleOutputStreamOperator<Student> student = env.addSource(new FlinkKafkaConsumer011<>(
                    "student",   //这个 kafka topic 需要和上面的工具类的 topic 一致
                    new SimpleStringSchema(),
                    props)).setParallelism(1)
                    .map(string -> JSON.parseObject(string, Student.class)); //Fastjson 解析字符串成 student 对象
    
            student.addSink(new SinkToMySQL()); //数据 sink 到 mysql
    
            env.execute("Flink add sink");
        }
    }

## 结果 ##

运行 Flink 程序，然后再运行 KafkaUtils2.java 工具类，这样就可以了。

如果数据插入成功了，那么我们查看下我们的数据库：

![Image 1][]

数据库中已经插入了 100 条我们从 Kafka 发送的数据了。证明我们的 SinkToMySQL 起作用了。

原创地址为：[http://www.54tianzhisheng.cn/2018/10/28/flink-sources/][http_www.54tianzhisheng.cn_2018_10_28_flink-sources]

[Image 1]: 
[http_www.54tianzhisheng.cn_2018_10_28_flink-sources]: http://www.54tianzhisheng.cn/2018/10/28/flink-sources/