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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@Overridepublic String toString() {return "WaterSensor{" +"id='" + id + '\'' +", ts=" + ts +", vc=" + vc +'}';}//重写equals和hasCode方法@Overridepublic 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);}@Overridepublic 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> {@Overridepublic 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 SourceDataStreamSource<String> dataStreamSource = streamExecutionEnvironment.socketTextStream("localhost", 8888);//TODO TransferSingleOutputStreamOperator<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>() {@Overridepublic 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MysqlwaterSensorSingleOutputStreamOperator.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