com.google.appengine.tools.mapreduce.inputs

Class ForwardingInputReader<T>

java.lang.Object

com.google.appengine.tools.mapreduce.InputReader<T>

com.google.appengine.tools.mapreduce.inputs.ForwardingInputReader<T>

Type Parameters:

T - type of values returned by this reader

All Implemented Interfaces:

Serializable

public abstract class ForwardingInputReader<T>
extends InputReader<T>

An InputReader delegates to another implementation.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ForwardingInputReader()

Method Summary

Methods

Modifier and Type	Method and Description
void	beginShard() Performs setup at the beginning of the shard.
void	beginSlice() Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.
void	endShard() Called after endSlice if there will not be any subsequent calls to beginSlice or next.
void	endSlice() Prepares the InputReader for serialization.
long	estimateMemoryRequirement() Returns the estimated memory that will be used by this reader in bytes.
ShardContext	getContext() Returns the current context, or null if none.
protected abstract InputReader<T>	getDelegate()
Double	getProgress() Returns the relative progress reading this input as a number from 0 to 1.
T	next() Returns the next input value, or throws NoSuchElementException when there is no more input data.
void	setContext(ShardContext context) Used internally to sets the context to be used for the processing that follows.

Methods inherited from class com.google.appengine.tools.mapreduce.InputReader

close, open

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardingInputReader

public ForwardingInputReader()

Method Detail

getDelegate

protected abstract InputReader<T> getDelegate()

next

public T next()
       throws IOException,
              NoSuchElementException

Description copied from class: InputReader

Returns the next input value, or throws NoSuchElementException when there is no more input data. This is done rather than providing a hasNext() function, to allow the implementation to deal with streams and remain serializable, even if the item being read is not.

Specified by:

next in class InputReader<T>

Throws:

IOException

NoSuchElementException

getProgress

public Double getProgress()

Description copied from class: InputReader

Returns the relative progress reading this input as a number from 0 to 1. Returns null if relative progress cannot be determined.

Overrides:

getProgress in class InputReader<T>

beginSlice

public void beginSlice()
                throws IOException

Description copied from class: InputReader

Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.

Overrides:

beginSlice in class InputReader<T>

Throws:

IOException - in the event of failure

endSlice

public void endSlice()
              throws IOException

Description copied from class: InputReader

Prepares the InputReader for serialization.

Overrides:

endSlice in class InputReader<T>

Throws:

IOException - in the event of failure

beginShard

public void beginShard()
                throws IOException

Description copied from class: InputReader

Performs setup at the beginning of the shard. This method is invoked before the first call to InputReader.beginSlice(). It will not be invoked again unless the shard restarts. When a shard is restarted, this method is invoked and the input should be read from the beginning.

Overrides:

beginShard in class InputReader<T>

Throws:

IOException - in the event of failure

endShard

public void endShard()
              throws IOException

Description copied from class: InputReader

Called after endSlice if there will not be any subsequent calls to beginSlice or next. This may be used to teardown or finalize any state if required.

Overrides:

endShard in class InputReader<T>

Throws:

IOException - in the event of failure

estimateMemoryRequirement

public long estimateMemoryRequirement()

Description copied from class: InputReader

Returns the estimated memory that will be used by this reader in bytes. (This is normally just set to the size of the buffers used by the implementation)

Overrides:

estimateMemoryRequirement in class InputReader<T>

setContext

public void setContext(ShardContext context)

Description copied from class: InputReader

Used internally to sets the context to be used for the processing that follows.

Overrides:

setContext in class InputReader<T>

getContext

public ShardContext getContext()

Description copied from class: InputReader

Returns the current context, or null if none.

Overrides:

getContext in class InputReader<T>