本文将会实现flink连接MySQL，废话不多说，上代码。本文章中的数据库表名为token，只有两个字段code和state

1、pom.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>flink-demo1</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>flink-mysql</artifactId>

    <properties>
        <java.version>1.8</java.version>
        <maven.compiler.source>${java.version}</maven.compiler.source>
        <maven.compiler.target>${java.version}</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.17</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.flink/flink-jdbc -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-jdbc_2.12</artifactId>
            <version>1.10.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_2.12</artifactId>
            <version>1.12.2</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients_2.12</artifactId>
            <version>1.12.2</version>
        </dependency>
    </dependencies>
</project>

2、读取数据源

import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.functions.source.RichSourceFunction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;


public class MysqlSource extends RichSourceFunction<TokenVO> {

    private static final Logger logger = LoggerFactory.getLogger(MysqlSource.class);
    private Connection connection = null;
    private PreparedStatement ps = null;
    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        //加载数据库驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //获取连接
        connection = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "123456");
        //构建读取SQL
        ps = connection.prepareStatement("select *  from token");
    }

    @Override
    public void run(SourceContext<TokenVO> sourceContext) throws Exception {
        try {
            //执行读取操作
            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next()) {
                TokenVO vo = new TokenVO();
                vo.setCode(resultSet.getString("code"));
                vo.setState(resultSet.getString("state"));
                sourceContext.collect(vo);
            }
        } catch (Exception e) {
            logger.error("runException:{}", e);
        }
    }

    @Override
    public void cancel() {
        try {
            super.close();
            if (connection != null) {
                connection.close();
            }
            if (ps != null) {
                ps.close();
            }
        } catch (Exception e) {
            logger.error("runException:{}", e);
        }
    }
}

3、更新和写入数据

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;

public class MysqlSink extends RichSinkFunction<TokenVO> {
    private Connection connection;
    private PreparedStatement preparedStatement;

    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        //加载数据库驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //获取连接
        connection = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "123");
        //构建执行SQL
        preparedStatement = connection.prepareStatement("UPDATE token SET code = ?,state = ?");
    }

    @Override
    public void close() throws Exception {
        super.close();
        if (preparedStatement != null) {
            preparedStatement.close();
        }
        if (connection != null) {
            connection.close();
        }
        super.close();
    }

    @Override
    public void invoke(TokenVO value, Context context) throws Exception {
        try {
            //添加新数据，执行SQL
            preparedStatement.setString(1, "new code 1");
            preparedStatement.setString(2, "new state 1");
            preparedStatement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4、启动类

import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

public class Test {
    public static void main(String[] args) throws Exception {
        //获取执行环境
        StreamExecutionEnvironment fsEnv = StreamExecutionEnvironment.getExecutionEnvironment();
        //获取数据源
        DataStreamSource<TokenVO> source = fsEnv.addSource(new MysqlSource());
        //输出数据
        source.addSink(new MysqlSink());
        //执行该逻辑
        fsEnv.execute();
    }
}

5、source、sink介绍

source

数据源是程序读取数据的来源，用户可以通过env.addSource(SourceFunction),将SourceFunction添加到程序中。Flink内置许多已知实现的SourceFunction，但是用户可以自定义实现SourceFunction(非并行化的接口)接口或者实现ParallelSourceFunction(并行化)接口，如果需要有状态管理还可以继承RichParallelSourceFunction

sink

Data Sink使用DataStreams并将其转发到文件，Socket，外部系统或打印它们。Flink带有多种内置输出格式，这些格式封装在DataStreams的操作后面。

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