org.apache.storm.trident.operation.builtin

Class Negate

java.lang.Object

org.apache.storm.trident.operation.builtin.Negate

All Implemented Interfaces:

Serializable, EachOperation, Filter, Operation

public class Negate
extends Object
implements Filter

A Filter implementation that inverts another delegate Filter.

The Negate.isKeep() method simply returns the opposite of the delegate’s isKeep() method:

public boolean isKeep(TridentTuple tuple) {
     return !this.delegate.isKeep(tuple);
}

The Negate filter is useful for dividing a Stream in two based on some boolean condition.

Suppose we had a Stream named userStream containing information about users, and a custom Filter implementation, RegisteredUserFilter that filtered out unregistered users. We could divide the userStream Stream into two separate Streams – one for registered users, and one for unregistered users – by doing the following:

Stream userStream = ...

Filter registeredFilter = new ResisteredUserFilter();
Filter unregisteredFilter = new Negate(registeredFilter);

Stream registeredUserStream = userStream.each(userStream.getOutputFields(), registeredFilter);
Stream unregisteredUserStream = userStream.each(userStream.getOutputFields(), unregisteredFilter);

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Negate(Filter delegate)

Method Summary

Modifier and Type	Method and Description
void	cleanup() When running in local mode, called when the local cluster is being shut down.
boolean	isKeep(TridentTuple tuple) Determines if a tuple should be filtered out of a stream
void	prepare(Map conf, TridentOperationContext context) Called when the Operation is first initialized.

Methods inherited from class java.lang.Object

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

Constructor Detail

Negate

public Negate(Filter delegate)

Method Detail

isKeep

public boolean isKeep(TridentTuple tuple)

Description copied from interface: Filter

Determines if a tuple should be filtered out of a stream

Specified by:

isKeep in interface Filter

Parameters:

tuple - the tuple being evaluated

Returns:

false to drop the tuple, true to keep the tuple

prepare

public void prepare(Map conf,
                    TridentOperationContext context)

Description copied from interface: Operation

Called when the Operation is first initialized.

Specified by:

prepare in interface Operation

Parameters:

conf - the Storm configuration map

context - the operation context which provides information such as the number of partitions in the stream, and the current partition index. It also provides methods for registering operation-specific metrics.

See Also:

TridentOperationContext

cleanup

public void cleanup()

Description copied from interface: Operation

When running in local mode, called when the local cluster is being shut down.

Specified by:

cleanup in interface Operation