cascading.operation.expression
Class ExpressionFilter

java.lang.Object
  cascading.operation.BaseOperation<ExpressionOperation.Context>
      cascading.operation.expression.ExpressionOperation
          cascading.operation.expression.ExpressionFilter

All Implemented Interfaces:

Filter<ExpressionOperation.Context>, Operation<ExpressionOperation.Context>, Serializable

public class ExpressionFilter
extends ExpressionOperation
implements Filter<ExpressionOperation.Context>

Class ExpressionFilter dynamically resolves a given expression using argument Tuple values. Any Tuple that returns true for the given expression will be removed from the stream. This Filter is based on the Janino compiler.

Specifically this filter uses the ExpressionEvaluator, thus the syntax from that class is inherited here.

An expression may use field names directly as parameters in the expression, or field positions with the syntax "$n", where n is an integer.

Given an argument tuple with the fields "a" and "b", the following expression returns true:
a + b == $0 + $1

Further, the types of the tuple elements will be coerced into the given parameterTypes. Regardless of the actual tuple element values, they will be converted to the types expected by the expression.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class cascading.operation.expression.ExpressionOperation

ExpressionOperation.Context

Field Summary

Fields inherited from class cascading.operation.expression.ExpressionOperation

expression

Fields inherited from class cascading.operation.BaseOperation

fieldDeclaration, numArgs, trace

Fields inherited from interface cascading.operation.Operation

ANY

Constructor Summary

ExpressionFilter(String expression, Class parameterType)
Constructor ExpressionFilter creates a new ExpressionFilter instance.

ExpressionFilter(String expression, String[] parameterNames, Class[] parameterTypes)
Constructor ExpressionFilter creates a new ExpressionFilter instance.

Method Summary

boolean

isRemove(FlowProcess flowProcess, FilterCall<ExpressionOperation.Context> filterCall) Method isRemove returns true if input should be removed from the tuple stream.

Methods inherited from class cascading.operation.expression.ExpressionOperation

equals, evaluate, hashCode, prepare

Methods inherited from class cascading.operation.BaseOperation

cleanup, flush, getFieldDeclaration, getNumArgs, getTrace, isSafe, printOperationInternal, toString, toStringInternal

Methods inherited from class java.lang.Object

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

Methods inherited from interface cascading.operation.Operation

cleanup, flush, getFieldDeclaration, getNumArgs, isSafe, prepare

Constructor Detail

ExpressionFilter

@ConstructorProperties(value={"expression","parameterType"})
public ExpressionFilter(String expression,
                                                   Class parameterType)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

Parameters:

expression - of type String

parameterType - of type Class

ExpressionFilter

@ConstructorProperties(value={"expression","parameterNames","parameterTypes"})
public ExpressionFilter(String expression,
                                                   String[] parameterNames,
                                                   Class[] parameterTypes)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

Parameters:

expression - of type String

parameterNames - of type String[]

parameterTypes - of type Class[]

Method Detail

isRemove

public boolean isRemove(FlowProcess flowProcess,
                        FilterCall<ExpressionOperation.Context> filterCall)

Description copied from interface: Filter

Method isRemove returns true if input should be removed from the tuple stream.

Specified by:

isRemove in interface Filter<ExpressionOperation.Context>

Parameters:

flowProcess - of type FlowProcess

filterCall - of type FilterCall

Returns:

boolean