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:

```java 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:

```java 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<String,Object> 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<String,Object> 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