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007-DataStream与MySql自定义sink和source(Scala版)002

三、自定义source

1.source主程序

package code.book.stream.customsinkandsource.jdbc.scalaimport java.sql.{Connection, DriverManager, PreparedStatement}import org.apache.flink.configuration.Configurationimport org.apache.flink.streaming.api.functions.source.RichSourceFunctionimport org.apache.flink.streaming.api.functions.source.SourceFunction.SourceContextclass StudentSourceFromMysql extends RichSourceFunction[Student] {  private var connection: Connection = null  private var ps: PreparedStatement = null  /**    * 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 def open(parameters: Configuration): Unit = {    super.open(parameters)    val driver = "com.mysql.jdbc.Driver"    val url = "jdbc:mysql://qingcheng11:3306/flinktest"    val username = "root"    val 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    val 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 def run(sourceContext: SourceContext[Student]): Unit = {    try {      //4.执行查询，封装数据      val resultSet = ps.executeQuery()      while (resultSet.next()) {        val student = Student(resultSet.getInt("stuid"), resultSet.getString("stuname").trim,         resultSet.getString("stuaddr").trim, resultSet.getString("stusex").trim)        sourceContext.collect(student)      }    } catch {      case e: Exception => println(e.getMessage)    }  }  override def cancel(): Unit = {  }  /**    * 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 def close(): Unit = {    //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.scalaimport org.apache.flink.streaming.api.scala.{StreamExecutionEnvironment, _}object StudentSourceFromMysqlTest {  def main(args: Array[String]): Unit = {    //1.创建流执行环境    val env = StreamExecutionEnvironment.getExecutionEnvironment    //2.从自定义source中读取数据    val dataStream: DataStream[Student] = env.addSource(new StudentSourceFromMysql)    //3.显示结果    dataStream.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。