云星数据---Apache Flink实战系列(精品版)】：Flink流处理API详解与编程实战010-DataStream与MySql自定义sink和source(Java版)002

三、自定义source

1.自定义source

package code.book.stream.customsinkandsource.jdbc.java;import org.apache.flink.configuration.Configuration;import org.apache.flink.streaming.api.functions.source.RichSourceFunction;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;public class StudentSourceFromMysql extends RichSourceFunction<Student> {    PreparedStatement ps;    private Connection connection;    /**     * 一、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。     */    @Override    public void open(Configuration parameters) throws Exception {        super.open(parameters);        String driver = "com.mysql.jdbc.Driver";        String url = "jdbc:mysql://qingcheng11:3306/flinktest";        String username = "root";        String password = "qingcheng";        //1.加载驱动        Class.forName(driver);        //2.创建连接        connection = DriverManager.getConnection(url, username, password);        //3.获得执行语句        String sql = "select stuid,stuname,stuaddr,stusex from Student;";        ps = connection.prepareStatement(sql);    }    /**     * 二、DataStream调用一次run()方法用来获取数据     */    @Override    public void run(SourceContext<Student> sourceContext) throws Exception {        try {            //4.执行查询，封装数据            ResultSet resultSet = ps.executeQuery();            while (resultSet.next()) {                Student student = new Student(                resultSet.getInt("stuid"),                resultSet.getString("stuname").trim(),                resultSet.getString("stuaddr").trim(),                 resultSet.getString("stusex").trim());                sourceContext.collect(student);            }        } catch (Exception e) {            e.printStackTrace();        }    }    @Override    public void cancel() {    }    /**     * 三、 程序执行完毕就可以进行，关闭连接和释放资源的动作了     */    @Override    public void close() throws Exception {        //5.关闭连接和释放资源        super.close();        if (connection != null) {            connection.close();        }        if (ps != null) {            ps.close();        }    }}

2.source测试程序

package code.book.stream.customsinkandsource.jdbc.java;import org.apache.flink.streaming.api.datastream.DataStream;import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;public class StudentSourceFromMysqlTest {    public static void main(String[] args) throws Exception {        //1.创建流执行环境        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();        //2.从自定义source中读取数据        DataStream<Student> students=env.addSource(new StudentSourceFromMysql());        //3.显示结果        students.print();        //4.触发流执行        env.execute();    }}

3.source测试效果

能够正确查询出mysql中的数据。