Flink--将表转换为DataStream或DataSet

A Table可以转换成a DataStream或DataSet。通过这种方式，可以在Table API或SQL查询的结果上运行自定义的DataStream或DataSet程序

将表转换为DataStream

有两种模式可以将 Table转换为DataStream：

1：Append Mode

将一个表附加到流上

2：Retract Mode

将表转换为流

语法格式：

 

// get TableEnvironment. 
// registration of a DataSet is equivalent
// ge val tableEnv = TableEnvironment.getTableEnvironment(env)

// Table with two fields (String name, Integer age)
val table: Table = ...

// convert the Table into an append DataStream of Row
val dsRow: DataStream[Row] = tableEnv.toAppendStream[Row](table)

// convert the Table into an append DataStream of Tuple2[String, Int]
val dsTuple: DataStream[(String, Int)] dsTuple = 
  tableEnv.toAppendStream[(String, Int)](table)

// convert the Table into a retract DataStream of Row.
//   A retract stream of type X is a DataStream[(Boolean, X)]. 
//   The boolean field indicates the type of the change. 
//   True is INSERT, false is DELETE.
val retractStream: DataStream[(Boolean, Row)] = tableEnv.toRetractStream[Row](table)

例子:

object TableTODataSet_DataStream {
  def main(args: Array[String]): Unit = {
    //构造数据，转换为table
    val data = List(
      Peoject(1L, 1, "Hello"),
      Peoject(2L, 2, "Hello"),
      Peoject(3L, 3, "Hello"),
      Peoject(4L, 4, "Hello"),
      Peoject(5L, 5, "Hello"),
      Peoject(6L, 6, "Hello"),
      Peoject(7L, 7, "Hello World"),
      Peoject(8L, 8, "Hello World"),
      Peoject(8L, 8, "Hello World"),
      Peoject(20L, 20, "Hello World"))

    val env = StreamExecutionEnvironment.getExecutionEnvironment
    env.setParallelism(1)
    val tEnv = TableEnvironment.getTableEnvironment(env)
    val stream = env.fromCollection(data)
    val table: Table = tEnv.fromDataStream(stream)
    //TODO 将table转换为DataStream----将一个表附加到流上Append Mode
    val appendStream: DataStream[Peoject] = tEnv.toAppendStream[Peoject](table)
    //TODO 将表转换为流Retract Mode true代表添加消息，false代表撤销消息
    val retractStream: DataStream[(Boolean, Peoject)] = tEnv.toRetractStream[Peoject](table)
    retractStream.print()
    env.execute()

  }
}

case class Peoject(user: Long, index: Int, content: String)

将表转换为DataSet

语法格式：

// get TableEnvironment 
// registration of a DataSet is equivalent
val tableEnv = TableEnvironment.getTableEnvironment(env)

// Table with two fields (String name, Integer age)
val table: Table = ...

// convert the Table into a DataSet of Row
val dsRow: DataSet[Row] = tableEnv.toDataSet[Row](table)

// convert the Table into a DataSet of Tuple2[String, Int]
val dsTuple: DataSet[(String, Int)] = tableEnv.toDataSet[(String, Int)](table)

例子：

case class Peoject(user: Long, index: Int, content: String)

object TableTODataSet{
  def main(args: Array[String]): Unit = {

    //构造数据，转换为table
    val data = List(
      Peoject(1L, 1, "Hello"),
      Peoject(2L, 2, "Hello"),
      Peoject(3L, 3, "Hello"),
      Peoject(4L, 4, "Hello"),
      Peoject(5L, 5, "Hello"),
      Peoject(6L, 6, "Hello"),
      Peoject(7L, 7, "Hello World"),
      Peoject(8L, 8, "Hello World"),
      Peoject(8L, 8, "Hello World"),
      Peoject(20L, 20, "Hello World"))
    //初始化环境，加载table数据
    val env = ExecutionEnvironment.getExecutionEnvironment
    env.setParallelism(1)
    val tableEnvironment = TableEnvironment.getTableEnvironment(env)
    val collection: DataSet[Peoject] = env.fromCollection(data)
    val table: Table = tableEnvironment.fromDataSet(collection)
    //TODO 将table转换为dataSet
    val toDataSet: DataSet[Peoject] = tableEnvironment.toDataSet[Peoject](table)
    toDataSet.print()
//    env.execute()
  }
}