org.apache.flink.streaming.api.functions.source

Class FromElementsFunction<T>

java.lang.Object

org.apache.flink.streaming.api.functions.source.FromElementsFunction<T>

Type Parameters:

T - The type of elements returned by this function.

All Implemented Interfaces:

Serializable, Function, Checkpointed<Integer>, CheckpointedAsynchronously<Integer>, SourceFunction<T>

public class FromElementsFunction<T>
extends Object
implements SourceFunction<T>, CheckpointedAsynchronously<Integer>

A stream source function that returns a sequence of elements.

Upon construction, this source function serializes the elements using Flink's type information. That way, any object transport using Java serialization will not be affected by the serializability of the elements.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.streaming.api.functions.source.SourceFunction

SourceFunction.SourceContext<T>

Constructor Summary

Constructors

Constructor and Description
FromElementsFunction(TypeSerializer<T> serializer, Iterable<T> elements)
FromElementsFunction(TypeSerializer<T> serializer, T... elements)

Method Summary

Methods

Modifier and Type	Method and Description
void	cancel() Cancels the source.
static <OUT> void	checkCollection(Collection<OUT> elements, Class<OUT> viewedAs) Verifies that all elements in the collection are non-null, and are of the given class, or a subclass thereof.
int	getNumElements() Gets the number of elements produced in total by this function.
int	getNumElementsEmitted() Gets the number of elements emitted so far.
void	restoreState(Integer state) Restores the state of the function or operator to that of a previous checkpoint.
void	run(SourceFunction.SourceContext<T> ctx) Starts the source.
Integer	snapshotState(long checkpointId, long checkpointTimestamp) Gets the current state of the function of operator.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FromElementsFunction

public FromElementsFunction(TypeSerializer<T> serializer,
                    T... elements)
                     throws IOException

Throws:

IOException

FromElementsFunction

public FromElementsFunction(TypeSerializer<T> serializer,
                    Iterable<T> elements)
                     throws IOException

Throws:

IOException

Method Detail

run

public void run(SourceFunction.SourceContext<T> ctx)
         throws Exception

Description copied from interface: SourceFunction

Starts the source. You can use the Collector parameter to emit elements. Sources that implement Checkpointed must lock on the checkpoint lock (using a synchronized block) before updating internal state and/or emitting elements. Also, the update of state and emission of elements must happen in the same synchronized block.

Specified by:

run in interface SourceFunction<T>

Parameters:

ctx - The context for interaction with the outside world.

Throws:

Exception

cancel

public void cancel()

Description copied from interface: SourceFunction

Cancels the source. Most sources will have a while loop inside the SourceFunction.run(org.apache.flink.streaming.api.functions.source.SourceFunction.SourceContext<T>) method. You need to ensure that the source will break out of this loop. This can be achieved by having a volatile field "isRunning" that is checked in the loop and that is set to false in this method.

Specified by:

cancel in interface SourceFunction<T>

getNumElements

public int getNumElements()

Gets the number of elements produced in total by this function.

Returns:

The number of elements produced in total.

getNumElementsEmitted

public int getNumElementsEmitted()

Gets the number of elements emitted so far.

Returns:

The number of elements emitted so far.

snapshotState

public Integer snapshotState(long checkpointId,
                    long checkpointTimestamp)

Description copied from interface: Checkpointed

Gets the current state of the function of operator. The state must reflect the result of all prior invocations to this function.

Specified by:

snapshotState in interface Checkpointed<Integer>

Parameters:

checkpointId - The ID of the checkpoint.

checkpointTimestamp - The timestamp of the checkpoint, as derived by System.currentTimeMillis() on the JobManager.

Returns:

A snapshot of the operator state.

restoreState

public void restoreState(Integer state)

Description copied from interface: Checkpointed

Restores the state of the function or operator to that of a previous checkpoint. This method is invoked when a function is executed as part of a recovery run. Note that restoreState() is called before open().

Specified by:

restoreState in interface Checkpointed<Integer>

Parameters:

state - The state to be restored.

checkCollection

public static <OUT> void checkCollection(Collection<OUT> elements,
                         Class<OUT> viewedAs)

Verifies that all elements in the collection are non-null, and are of the given class, or a subclass thereof.

Type Parameters:

OUT - The generic type of the collection to be checked.

Parameters:

elements - The collection to check.

viewedAs - The class to which the elements must be assignable to.