cascading.scheme

Class NullScheme<Config,Input,Output,SourceContext,SinkContext>

java.lang.Object

cascading.scheme.Scheme<Config,Input,Output,SourceContext,SinkContext>

cascading.scheme.NullScheme<Config,Input,Output,SourceContext,SinkContext>

All Implemented Interfaces:

Traceable, java.io.Serializable

public class NullScheme<Config,Input,Output,SourceContext,SinkContext>
extends Scheme<Config,Input,Output,SourceContext,SinkContext>

Class NullScheme is a Scheme that neither reads or writes any values.

It is typically used as a placeholder where a Scheme instance is needed but generally ignored.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
NullScheme()
NullScheme(Fields sourceFields, Fields sinkFields)

Method Summary

Modifier and Type	Method and Description
void	sink(FlowProcess<? extends Config> flowProcess, SinkCall<SinkContext,Output> sinkCall) Method sink writes out the given Tuple found on SinkCall.getOutgoingEntry() to the SinkCall.getOutput().
void	sinkConfInit(FlowProcess<? extends Config> flowProcess, Tap<Config,Input,Output> tap, Config conf) Method sinkInit initializes this instance as a sink.
boolean	source(FlowProcess<? extends Config> flowProcess, SourceCall<SourceContext,Input> sourceCall) Method source will read a new "record" or value from SourceCall.getInput() and populate the available Tuple via SourceCall.getIncomingEntry() and return true on success or false if no more values available.
void	sourceConfInit(FlowProcess<? extends Config> flowProcess, Tap<Config,Input,Output> tap, Config conf) Method sourceInit initializes this instance as a source.
java.lang.String	toString()

Methods inherited from class cascading.scheme.Scheme

equals, getNumSinkParts, getSinkFields, getSourceFields, getTrace, hashCode, isSink, isSource, isSymmetrical, presentSinkFields, presentSinkFieldsInternal, presentSourceFields, presentSourceFieldsInternal, retrieveSinkFields, retrieveSourceFields, setNumSinkParts, setSinkFields, setSourceFields, sinkCleanup, sinkPrepare, sinkWrap, sourceCleanup, sourcePrepare, sourceRePrepare, sourceWrap

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

NullScheme

public NullScheme()

NullScheme

public NullScheme(Fields sourceFields,
                  Fields sinkFields)

Method Detail

sourceConfInit

public void sourceConfInit(FlowProcess<? extends Config> flowProcess,
                           Tap<Config,Input,Output> tap,
                           Config conf)

Description copied from class: Scheme

Method sourceInit initializes this instance as a source.

This method is executed client side as a means to provide necessary configuration parameters used by the underlying platform.

It is not intended to initialize resources that would be necessary during the execution of this class, like a "formatter" or "parser".

See Scheme.sourcePrepare(cascading.flow.FlowProcess, SourceCall) if resources much be initialized before use. And Scheme.sourceCleanup(cascading.flow.FlowProcess, SourceCall) if resources must be destroyed after use.

Specified by:

sourceConfInit in class Scheme<Config,Input,Output,SourceContext,SinkContext>

Parameters:

flowProcess - of type FlowProcess

tap - of type Tap

conf - of type Config

sinkConfInit

public void sinkConfInit(FlowProcess<? extends Config> flowProcess,
                         Tap<Config,Input,Output> tap,
                         Config conf)

Description copied from class: Scheme

Method sinkInit initializes this instance as a sink.

This method is executed client side as a means to provide necessary configuration parameters used by the underlying platform.

It is not intended to initialize resources that would be necessary during the execution of this class, like a "formatter" or "parser".

See Scheme.sinkPrepare(cascading.flow.FlowProcess, SinkCall) if resources much be initialized before use. And Scheme.sinkCleanup(cascading.flow.FlowProcess, SinkCall) if resources must be destroyed after use.

Specified by:

sinkConfInit in class Scheme<Config,Input,Output,SourceContext,SinkContext>

Parameters:

flowProcess - of type FlowProcess

tap - of type Tap

conf - of type Config

source

public boolean source(FlowProcess<? extends Config> flowProcess,
                      SourceCall<SourceContext,Input> sourceCall)
               throws java.io.IOException

Description copied from class: Scheme

Method source will read a new "record" or value from SourceCall.getInput() and populate the available Tuple via SourceCall.getIncomingEntry() and return true on success or false if no more values available.

It's ok to set a new Tuple instance on the incomingEntry TupleEntry, or to simply re-use the existing instance.

Note this is only time it is safe to modify a Tuple instance handed over via a method call.

This method may optionally throw a TapException if it cannot process a particular instance of data. If the payload Tuple is set on the TapException, that Tuple will be written to any applicable failure trap Tap.

Specified by:

source in class Scheme<Config,Input,Output,SourceContext,SinkContext>

Parameters:

flowProcess - of type FlowProcess

sourceCall - of SourceCall

Returns:

returns true when a Tuple was successfully read

Throws:

java.io.IOException

sink

public void sink(FlowProcess<? extends Config> flowProcess,
                 SinkCall<SinkContext,Output> sinkCall)
          throws java.io.IOException

Description copied from class: Scheme

Method sink writes out the given Tuple found on SinkCall.getOutgoingEntry() to the SinkCall.getOutput().

This method may optionally throw a TapException if it cannot process a particular instance of data. If the payload Tuple is set on the TapException, that Tuple will be written to any applicable failure trap Tap. If not set, the incoming Tuple will be written instead.

Specified by:

sink in class Scheme<Config,Input,Output,SourceContext,SinkContext>

Parameters:

flowProcess - of Process

sinkCall - of SinkCall

Throws:

java.io.IOException

toString

public java.lang.String toString()

Overrides:

toString in class Scheme<Config,Input,Output,SourceContext,SinkContext>