一、写在前面

在实际的生产环境中，我们经常会把Flink处理的数据写入MySQL、Doris等数据库中，下面以MySQL为例，使用JDBC的方式将Flink的数据实时数据写入MySQL。

二、代码示例

2.1 版本说明

        <flink.version>1.14.6</flink.version>
        <spark.version>2.4.3</spark.version>
        <hadoop.version>2.8.5</hadoop.version>
        <hbase.version>1.4.9</hbase.version>
        <hive.version>2.3.5</hive.version>
        <java.version>1.8</java.version>
        <scala.version>2.11.8</scala.version>
        <mysql.version>8.0.22</mysql.version>
        <scala.binary.version>2.11</scala.binary.version>

2.2 导入相关依赖

 <dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-connector-jdbc_2.11</artifactId>
    <version>${flink.version}</version>
</dependency>
<!--mysql连接器依赖-->
<dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>8.0.22</version>
</dependency>

2.3 连接数据库，创建表

mysql> CREATE TABLE `ws` ( 
      `id` varchar(100) NOT NULL
      ,`ts` bigint(20) DEFAULT NULL
      ,`vc` int(11) DEFAULT NULL, PRIMARY KEY (`id`) 
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8

2.4 创建POJO类

package com.flink.POJOs;


import java.util.Objects;

/**
 * TODO POJO类的特点
 * 类是公有（public）的
 * 有一个无参的构造方法
 * 所有属性都是公有（public）的
 * 所有属性的类型都是可以序列化的
 */
public class WaterSensor {
    
    //类的公共属性
    public String id;
    public Long ts;
    public Integer vc;

    //无参构造方法
    public WaterSensor() {
    
        //System.out.println("调用了无参数的构造方法");
    }

    public WaterSensor(String id, Long ts, Integer vc) {
    
        this.id = id;
        this.ts = ts;
        this.vc = vc;
    }

    //生成get和set方法
    public void setId(String id) {
    
        this.id = id;
    }

    public void setTs(Long ts) {
    
        this.ts = ts;
    }

    public void setVc(Integer vc) {
    
        this.vc = vc;
    }

    public String getId() {
    
        return id;
    }

    public Long getTs() {
    
        return ts;
    }

    public Integer getVc() {
    
        return vc;
    }

    //重写toString方法
    @Override
    public String toString() {
    
        return "WaterSensor{" +
                "id='" + id + '\'' +
                ", ts=" + ts +
                ", vc=" + vc +
                '}';
    }

    //重写equals和hasCode方法
    @Override
    public boolean equals(Object o) {
    
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        WaterSensor that = (WaterSensor) o;
        return id.equals(that.id) && ts.equals(that.ts) && vc.equals(that.vc);
    }

    @Override
    public int hashCode() {
    
        return Objects.hash(id, ts, vc);
    }
}
//scala的case类？

2.5 自定义map函数

package com.flink.POJOs;

import org.apache.flink.api.common.functions.MapFunction;

public class WaterSensorMapFunction implements MapFunction<String, WaterSensor> {
    
    @Override
    public WaterSensor map(String value) throws Exception {
    
        String[] datas = value.split(",");
        return new WaterSensor(datas[0], Long.valueOf(datas[1]), Integer.valueOf(datas[2]));
    }
}

2.5 Flink2MySQL

package com.flink.DataStream.Sink;

import com.flink.POJOs.WaterSensor;
import com.flink.POJOs.WaterSensorMapFunction;
import org.apache.flink.connector.jdbc.JdbcConnectionOptions;
import org.apache.flink.connector.jdbc.JdbcExecutionOptions;
import org.apache.flink.connector.jdbc.JdbcSink;
import org.apache.flink.connector.jdbc.JdbcStatementBuilder;
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.SinkFunction;

import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * Flink 输出到 MySQL（JDBC）
 */
public class flinkSinkJdbc {
    
    public static void main(String[] args) throws Exception {
    
        //TODO 创建Flink上下文执行环境
        StreamExecutionEnvironment streamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment();
        streamExecutionEnvironment.setParallelism(1);
        //TODO Source
        DataStreamSource<String> dataStreamSource = streamExecutionEnvironment.socketTextStream("localhost", 8888);
        //TODO Transfer
        SingleOutputStreamOperator<WaterSensor> waterSensorSingleOutputStreamOperator = dataStreamSource.map(new WaterSensorMapFunction());
        /**TODO 写入 mysql
         * 1、只能用老的 sink 写法
         * 2、JDBCSink 的 4 个参数:
         *   第一个参数： 执行的 sql，一般就是 insert into
         *   第二个参数： 预编译 sql， 对占位符填充值
         *   第三个参数： 执行选项 ---->攒批、重试
         *   第四个参数： 连接选项---->url、用户名、密码
         */
        SinkFunction<WaterSensor> sinkFunction = JdbcSink.sink("insert into ws values(?,?,?)",
                new JdbcStatementBuilder<WaterSensor>() {
    
                    @Override
                    public void accept(PreparedStatement preparedStatement, WaterSensor waterSensor) throws SQLException {
    
                        preparedStatement.setString(1, waterSensor.getId());
                        preparedStatement.setLong(2, waterSensor.getTs());
                        preparedStatement.setInt(3, waterSensor.getVc());
                        System.out.println("数据写入成功："+'('+waterSensor.getId()+","+waterSensor.getTs()+","+waterSensor.getVc()+")");
                    }
                }
                , JdbcExecutionOptions
                        .builder()
                        .withMaxRetries(3)         // 重试次数
                        .withBatchSize(100)        // 批次的大小：条数
                        .withBatchIntervalMs(3000) // 批次的时间
                        .build(),
                new JdbcConnectionOptions.JdbcConnectionOptionsBuilder()
                        .withUrl("jdbc:mysql://localhost:3306/dw?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=UTF-8")
                        .withUsername("root")
                        .withPassword("********")
                        .withConnectionCheckTimeoutSeconds(60) // 重试的超时时间
                        .build()
        );
        //TODO 写入到Mysql
        waterSensorSingleOutputStreamOperator.addSink(sinkFunction);

        streamExecutionEnvironment.execute();
    }
}

2.6 启动necat、Flink，观察数据库写入情况

nc -lk 9999 #启动necat、并监听8888端口，写入数据

启动Flink程序

查看数据库写入是否正常