cascading.operation.expression
Class ExpressionFilter

java.lang.Object
  cascading.operation.BaseOperation
      cascading.operation.expression.ExpressionOperation
          cascading.operation.expression.ExpressionFilter

All Implemented Interfaces:

Filter, Operation, Serializable

public class ExpressionFilter
extends ExpressionOperation
implements Filter

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.

Specifially 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

Field Summary

Fields inherited from class cascading.operation.expression.ExpressionOperation

expression, parameterTypes

Fields inherited from class cascading.operation.BaseOperation

fieldDeclaration, numArgs

Fields inherited from interface cascading.operation.Operation

ANY

Constructor Summary

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

Method Summary

boolean

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

Methods inherited from class cascading.operation.expression.ExpressionOperation

evaluate

Methods inherited from class cascading.operation.BaseOperation

getFieldDeclaration, getNumArgs, printOperationInternal, toString, toStringInternal

Methods inherited from class java.lang.Object

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

Methods inherited from interface cascading.operation.Operation

getFieldDeclaration, getNumArgs

Constructor Detail

ExpressionFilter

public ExpressionFilter(String expression,
                        Class... parameterTypes)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

Parameters:

expression - of type String

parameterTypes - of type Class[]

Method Detail

isRemove

public boolean isRemove(TupleEntry input)

Description copied from interface: Filter

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

Specified by:

isRemove in interface Filter

Parameters:

input - of type TupleEntry

Returns:

boolean

See Also:

Filter.isRemove(TupleEntry)