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本文主要研究一下flink的CsvTableSink
TableSink
flink-table_2.11-1.7.1-sources.jar!/org/apache/flink/table/sinks/TableSink.scala
trait TableSink[T] {
/**
* Returns the type expected by this [[TableSink]].
*
* This type should depend on the types returned by [[getFieldNames]].
*
* @return The type expected by this [[TableSink]].
*/
def getOutputType: TypeInformation[T]
/** Returns the names of the table fields. */
def getFieldNames: Array[String]
/** Returns the types of the table fields. */
def getFieldTypes: Array[TypeInformation[_]]
/**
* Return a copy of this [[TableSink]] configured with the field names and types of the
* [[Table]] to emit.
*
* @param fieldNames The field names of the table to emit.
* @param fieldTypes The field types of the table to emit.
* @return A copy of this [[TableSink]] configured with the field names and types of the
* [[Table]] to emit.
*/
def configure(fieldNames: Array[String],
fieldTypes: Array[TypeInformation[_]]): TableSink[T]
}
复制代码- TableSink定义了getOutputType、getFieldNames、getFieldTypes、configure三个方法
BatchTableSink
flink-table_2.11-1.7.1-sources.jar!/org/apache/flink/table/sinks/BatchTableSink.scala
trait BatchTableSink[T] extends TableSink[T] {
/** Emits the DataSet. */
def emitDataSet(dataSet: DataSet[T]): Unit
}
复制代码- BatchTableSink继承了TableSink，定义了emitDataSet方法
StreamTableSink
flink-table_2.11-1.7.1-sources.jar!/org/apache/flink/table/sinks/StreamTableSink.scala
trait StreamTableSink[T] extends TableSink[T] {
/** Emits the DataStream. */
def emitDataStream(dataStream: DataStream[T]): Unit
}
复制代码- StreamTableSink继承了TableSink，定义了emitDataStream方法
TableSinkBase
flink-table_2.11-1.7.1-sources.jar!/org/apache/flink/table/sinks/TableSinkBase.scala
trait TableSinkBase[T] extends TableSink[T] {
private var fieldNames: Option[Array[String]] = None
private var fieldTypes: Option[Array[TypeInformation[_]]] = None
/** Return a deep copy of the [[TableSink]]. */
protected def copy: TableSinkBase[T]
/**
* Return the field names of the [[Table]] to emit. */
def getFieldNames: Array[String] = {
fieldNames match {
case Some(n) => n
case None => throw new IllegalStateException(
"TableSink must be configured to retrieve field names.")
}
}
/** Return the field types of the [[Table]] to emit. */
def getFieldTypes: Array[TypeInformation[_]] = {
fieldTypes match {
case Some(t) => t
case None => throw new IllegalStateException(
"TableSink must be configured to retrieve field types.")
}
}
/**
* Return a copy of this [[TableSink]] configured with the field names and types of the
* [[Table]] to emit.
*
* @param fieldNames The field names of the table to emit.
* @param fieldTypes The field types of the table to emit.
* @return A copy of this [[TableSink]] configured with the field names and types of the
* [[Table]] to emit.
*/
final def configure(fieldNames: Array[String],
fieldTypes: Array[TypeInformation[_]]): TableSink[T] = {
val configuredSink = this.copy
configuredSink.fieldNames = Some(fieldNames)
configuredSink.fieldTypes = Some(fieldTypes)
configuredSink
}
}
复制代码- TableSinkBase继承了TableSink，它实现了getFieldNames、getFieldTypes、configure方法
CsvTableSink
flink-table_2.11-1.7.1-sources.jar!/org/apache/flink/table/sinks/CsvTableSink.scala
class CsvTableSink(
path: String,
fieldDelim: Option[String],
numFiles: Option[Int],
writeMode: Option[WriteMode])
extends TableSinkBase[Row] with BatchTableSink[Row] with AppendStreamTableSink[Row] {
/**
* A simple [[TableSink]] to emit data as CSV files.
*
* @param path The output path to write the Table to.
* @param fieldDelim The field delimiter, ',' by default.
*/
def this(path: String, fieldDelim: String = ",") {
this(path, Some(fieldDelim), None, None)
}
/**
* A simple [[TableSink]] to emit data as CSV files.
*
* @param path The output path to write the Table to.
* @param fieldDelim The field delimiter.
* @param numFiles The number of files to write to.
* @param writeMode The write mode to specify whether existing files are overwritten or not.
*/
def this(path: String, fieldDelim: String, numFiles: Int, writeMode: WriteMode) {
this(path, Some(fieldDelim), Some(numFiles), Some(writeMode))
}
override def emitDataSet(dataSet: DataSet[Row]): Unit = {
val csvRows = dataSet.map(new CsvFormatter(fieldDelim.getOrElse(",")))
if (numFiles.isDefined) {
csvRows.setParallelism(numFiles.get)
}
val sink = writeMode match {
case None => csvRows.writeAsText(path)
case Some(wm) => csvRows.writeAsText(path, wm)
}
if (numFiles.isDefined) {
sink.setParallelism(numFiles.get)
}
sink.name(TableConnectorUtil.generateRuntimeName(this.getClass, getFieldNames))
}
override def emitDataStream(dataStream: DataStream[Row]): Unit = {
val csvRows = dataStream.map(new CsvFormatter(fieldDelim.getOrElse(",")))
if (numFiles.isDefined) {
csvRows.setParallelism(numFiles.get)
}
val sink = writeMode match {
case None => csvRows.writeAsText(path)
case Some(wm) => csvRows.writeAsText(path, wm)
}
if (numFiles.isDefined) {
sink.setParallelism(numFiles.get)
}
sink.name(TableConnectorUtil.generateRuntimeName(this.getClass, getFieldNames))
}
override protected def copy: TableSinkBase[Row] = {
new CsvTableSink(path, fieldDelim, numFiles, writeMode)
}
override def getOutputType: TypeInformation[Row] = {
new RowTypeInfo(getFieldTypes: _*)
}
}
/**
* Formats a [[Row]] into a [[String]] with fields separated by the field delimiter.
*
* @param fieldDelim The field delimiter.
*/
class CsvFormatter(fieldDelim: String) extends MapFunction[Row, String] {
override def map(row: Row): String = {
val builder = new StringBuilder
// write first value
val v = row.getField(0)
if (v != null) {
builder.append(v.toString)
}
// write following values
for (i <- 1 until row.getArity) {
builder.append(fieldDelim)
val v = row.getField(i)
if (v != null) {
builder.append(v.toString)
}
}
builder.mkString
}
}
/**
* Formats a [[Row]] into a [[String]] with fields separated by the field delimiter.
*
* @param fieldDelim The field delimiter.
*/
class CsvFormatter(fieldDelim: String) extends MapFunction[Row, String] {
override def map(row: Row): String = {
val builder = new StringBuilder
// write first value
val v = row.getField(0)
if (v != null) {
builder.append(v.toString)
}
// write following values
for (i <- 1 until row.getArity) {
builder.append(fieldDelim)
val v = row.getField(i)
if (v != null) {
builder.append(v.toString)
}
}
builder.mkString
}
}
复制代码- CsvTableSink继承了TableSinkBase，实现了BatchTableSink及AppendStreamTableSink接口，而AppendStreamTableSink则继承了StreamTableSink
- emitDataSet及emitDataStream都使用了CsvFormatter，它是一个MapFunction，将Row类型转换为String
- CsvTableSink有一个名为writeMode的可选参数，WriteMode是一个枚举，它有NO_OVERWRITE及OVERWRITE两个枚举值，用于写csv文件时指定是否要覆盖已有的同名文件
小结
- TableSink定义了getOutputType、getFieldNames、getFieldTypes、configure三个方法；BatchTableSink继承了TableSink，定义了emitDataSet方法；StreamTableSink继承了TableSink，定义了emitDataStream方法；TableSinkBase继承了TableSink，它实现了getFieldNames、getFieldTypes、configure方法
- CsvTableSink继承了TableSinkBase，实现了BatchTableSink及AppendStreamTableSink接口，而AppendStreamTableSink则继承了StreamTableSink；emitDataSet及emitDataStream都使用了CsvFormatter，它是一个MapFunction，将Row类型转换为String
- CsvTableSink有一个名为writeMode的可选参数，WriteMode是一个枚举，它有NO_OVERWRITE及OVERWRITE两个枚举值，用于写csv文件时指定是否要覆盖已有的同名文件