项目实战 从 0 到 1 学习之Flink（22）读mysql并写入mysql

在Flink文档中，提供connector读取源数据和把处理结果存储到外部系统中。但是没有提供数据库的connector，如果要读写数据库，官网给出了异步IO(Asynchronous I/O)专门用于访问外部数据，详细可看：

https://ci.apache.org/projects/flink/flink-docs-release-1.6/dev/stream/operators/asyncio.html

还有一种方法是继承RichSourceFunction，重写里面的方法，具体如下：

读取mysql的类：

package com.my.flink.utils.streaming.mysql;
 
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.functions.source.RichSourceFunction;
import org.apache.flink.streaming.api.functions.source.SourceFunction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import com.my.flink.utils.config.ConfigKeys;
 
/**
 * @Description mysql source
 * @Author jiangxiaozhi
 * @Date 2018/10/15 17:05
 **/
public class JdbcReader extends RichSourceFunction<Tuple2<String,String>> {
    private static final Logger logger = LoggerFactory.getLogger(JdbcReader.class);
 
    private Connection connection = null;
    private PreparedStatement ps = null;
 
    //该方法主要用于打开数据库连接，下面的ConfigKeys类是获取配置的类
    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        Class.forName(ConfigKeys.DRIVER_CLASS());//加载数据库驱动
        connection = DriverManager.getConnection(ConfigKeys.SOURCE_DRIVER_URL(), ConfigKeys.SOURCE_USER(), ConfigKeys.SOURCE_PASSWORD());//获取连接
        ps = connection.prepareStatement(ConfigKeys.SOURCE_SQL());
    }
 
    //执行查询并获取结果
    @Override
    public void run(SourceContext<Tuple2<String, String>> ctx) throws Exception {
        try {
            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next()) {
                String name = resultSet.getString("nick");
                String id = resultSet.getString("user_id");
                logger.error("readJDBC name:{}", name);
                Tuple2<String,String> tuple2 = new Tuple2<>();
                tuple2.setFields(id,name);
                ctx.collect(tuple2);//发送结果，结果是tuple2类型，2表示两个元素，可根据实际情况选择
            }
        } catch (Exception e) {
            logger.error("runException:{}", e);
        }
 
    }
     
    //关闭数据库连接
    @Override
    public void cancel() {
        try {
            super.close();
            if (connection != null) {
                connection.close();
            }
            if (ps != null) {
                ps.close();
            }
        } catch (Exception e) {
            logger.error("runException:{}", e);
        }
    }
}

 写入mysql的类：

package com.my.flink.utils.streaming.mysql;
 
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;
import org.apache.flink.streaming.api.functions.sink.SinkFunction;
import scala.Tuple2;
 
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import com.my.flink.utils.config.ConfigKeys;
 
/**
 * @Description mysql sink
 * @Author jiangxiaozhi
 * @Date 2018/10/15 18:31
 **/
public class JdbcWriter extends RichSinkFunction<Tuple2<String,String>> {
    private Connection connection;
    private PreparedStatement preparedStatement;
    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        // 加载JDBC驱动
        Class.forName(ConfigKeys.DRIVER_CLASS());
        // 获取数据库连接
        connection = DriverManager.getConnection(ConfigKeys.SINK_DRIVER_URL(),ConfigKeys.SINK_USER(),ConfigKeys.SINK_PASSWORD());//写入mysql数据库
        preparedStatement = connection.prepareStatement(ConfigKeys.SINK_SQL());//insert sql在配置文件中
        super.open(parameters);
    }
 
    @Override
    public void close() throws Exception {
        super.close();
        if(preparedStatement != null){
            preparedStatement.close();
        }
        if(connection != null){
            connection.close();
        }
        super.close();
    }
 
    @Override
    public void invoke(Tuple1<String,String> value, Context context) throws Exception {
        try {
            String name = value._1;//获取JdbcReader发送过来的结果
            preparedStatement.setString(1,name);
            preparedStatement.executeUpdate();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

程序入口核心代码：

  //scala代码
  val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
  env.enableCheckpointing(5000)
  env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
  env.getCheckpointConfig.setCheckpointingMode(CheckpointingMode.EXACTLY_ONCE)
  val dataStream =  env.addSource(new JdbcReader())//，读取mysql数据，获取dataStream后可以做逻辑处理，这里没有
做
  dataStream.addSink(new JdbcWriter())//写入mysql
  env.execute("flink mysql demo")//运行程序

运行程序就可以在数据库表中看到写入的数据了。