1.先写TestForeachWriter需要extends ForeachWriter，代码如下：

class TestForeachWriter extends ForeachWriter[Row] with Serializable {
    var connection:Connection = _
    var statement:Statement = _
    val ip = " "
    val port = "3306"
    val user = " "
    val database = " "
    val password = ""
    val url = s"jdbc:mysql://$ip:$port/$database?useUnicode=true&characterEncoding=UTF-8"

    override def open(partitionId: Long, version: Long): Boolean = {
        Class.forName("com.mysql.jdbc.Driver")
        connection = DriverManager.getConnection(url, user, password)
        statement = connection.createStatement
        true
    }

    override def process(value: Row): Unit = {
        statement.execute(s"insert into stream_word values ('${value.get(0)}',${value.get(1)})")
    }

    override def close(errorOrNull: Throwable): Unit = {
        connection.close()
    }
}

2.监控目录文件将数据插入mysql

def main(args: Array[String]): Unit = {
        val spark = SparkSession.builder().master("local[1]").getOrCreate()
        import spark.implicits._
        val wordCounts  = spark.readStream.text("D:\\tmp\\streaming\\struct")
            .as[String].flatMap(_.split(" "))
            .groupBy("value").count()

        val query = wordCounts.writeStream
                .foreach(new TestForeachWriter())
            .outputMode("complete")//complete  append
            .trigger(ProcessingTime("10 seconds"))
            .start()
        query.awaitTermination()

    }

3.向监控目录写文件

public static void main(String[] args) {
        try {
            FileOutputStream fos = new FileOutputStream("D:\\tmp\\streaming\\struct\\c.txt");
            try {
                fos.write("c c c c c\r\nb a b\r\nc a a".getBytes());
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }