public class MicrobatchSource.Reader extends Source.Reader<T>
BoundedReadFromUnboundedSource's
UnboundedToBoundedSourceAdapter, with some adjustments for Spark specifics.
This Reader reads until one of the following thresholds has been reached:
| Modifier and Type | Method and Description |
|---|---|
boolean |
advance()
Advances the reader to the next valid record.
|
void |
close()
Closes the reader.
|
CheckpointMarkT |
getCheckpointMark() |
T |
getCurrent()
Returns the value of the data item that was read by the last
Source.Reader.start() or Source.Reader.advance() call. |
Source<T> |
getCurrentSource()
Returns a
Source describing the same input that this Reader currently reads
(including items already read). |
Instant |
getCurrentTimestamp()
Returns the timestamp associated with the current data item.
|
Instant |
getWatermark() |
boolean |
start()
Initializes the reader and advances the reader to the first record.
|
public boolean start()
throws java.io.IOException
Source.ReaderThis method should be called exactly once. The invocation should occur prior to calling
Source.Reader.advance() or Source.Reader.getCurrent(). This method may perform expensive operations that
are needed to initialize the reader.
start in class Source.Reader<T>true if a record was read, false if there is no more input available.java.io.IOExceptionpublic boolean advance()
throws java.io.IOException
Source.ReaderIt is an error to call this without having called Source.Reader.start() first.
advance in class Source.Reader<T>true if a record was read, false if there is no more input available.java.io.IOExceptionpublic T getCurrent() throws java.util.NoSuchElementException
Source.ReaderSource.Reader.start() or Source.Reader.advance() call. The returned value must be effectively immutable and remain valid
indefinitely.
Multiple calls to this method without an intervening call to Source.Reader.advance() should
return the same result.
getCurrent in class Source.Reader<T>java.util.NoSuchElementException - if Source.Reader.start() was never called, or if the last
Source.Reader.start() or Source.Reader.advance() returned false.public Instant getCurrentTimestamp() throws java.util.NoSuchElementException
Source.ReaderIf the source does not support timestamps, this should return BoundedWindow.TIMESTAMP_MIN_VALUE.
Multiple calls to this method without an intervening call to Source.Reader.advance() should
return the same result.
getCurrentTimestamp in class Source.Reader<T>java.util.NoSuchElementException - if the reader is at the beginning of the input and Source.Reader.start() or Source.Reader.advance() wasn't called, or if the last Source.Reader.start() or Source.Reader.advance() returned false.public void close()
throws java.io.IOException
Source.Readerclose in interface java.lang.AutoCloseableclose in class Source.Reader<T>java.io.IOExceptionpublic Source<T> getCurrentSource()
Source.ReaderSource describing the same input that this Reader currently reads
(including items already read).
Usually, an implementation will simply return the immutable Source object from
which the current Source.Reader was constructed, or delegate to the base class. However,
when using or implementing this method on a BoundedSource.BoundedReader, special
considerations apply, see documentation for BoundedSource.BoundedReader.getCurrentSource().
getCurrentSource in class Source.Reader<T>public CheckpointMarkT getCheckpointMark()
public Instant getWatermark()