cascading.operation.expression
Class ExpressionFunction

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

All Implemented Interfaces:

Function, Operation, Serializable

public class ExpressionFunction
extends ExpressionOperation
implements Function

Class ExpressionFunction dynamically resolves a given expression using argument Tuple values. This Function is based on the Janino compiler.

Specifially this function 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

ExpressionFunction(Fields fieldDeclaration, String expression, Class... parameterTypes)
Constructor ExpressionFunction creates a new ExpressionFunction instance.

Method Summary

void	operate(TupleEntry input, TupleCollector outputCollector) Method operate provides the implementation of this Function.

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

ExpressionFunction

public ExpressionFunction(Fields fieldDeclaration,
                          String expression,
                          Class... parameterTypes)

Constructor ExpressionFunction creates a new ExpressionFunction instance.

Parameters:

fieldDeclaration - of type Fields

expression - of type String

parameterTypes - of type Class[]

Method Detail

operate

public void operate(TupleEntry input,
                    TupleCollector outputCollector)

Description copied from interface: Function

Method operate provides the implementation of this Function.

Specified by:

operate in interface Function

Parameters:

input - of type TupleEntry

outputCollector - of type TupleEntryListIterator

See Also:

Function.operate(cascading.tuple.TupleEntry,cascading.tuple.TupleCollector)